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THE PROPAGATION OF MICROWAVES ON LINE-OF-SIGHT OVERSEA PATHS

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CANADIAN THESES ON MICROFICHE
9
I.S.B.N.
THESES CANADIENNES SUR MICROFICHE
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PERMISSION TO MICROFILM — AUTORISATIONDE M1CROFILMER
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Please print or type — Ecrire en lettres moulees ou dactylographier
Full Name of Author—'Nom complet de I’auteur
'
.
WANG-LEUNG IGNATIUS LAM
--
Date of Birth- — Date de naissance
1955
Country of Birth — Lieu de naissance
HONG KONG
t
Permanent Address — Residence fixe
c /o . F acu lty o f Engineering S c ie n c e ,
E . M . S c . Bui j d i n g ,
The U n i v e r s i t y o f W estern O n t a r i o ,
L ondon, O n t a r i o N6A 3K7•
•
*»
Title of Thesis — Titre de la these
THE PROPAGATION OF MICROWAVES ON LINE-OF-SJGHT OVERSEA PATHS
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V
f
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6
University—1University
i
1
THE UNIVERSITY OF WESTERN “ONTARIO
»
Degree for which thesis was presented — Grade poui* lequel cettd these fut presentee
*
*
DOCTOR OF PHILOSOPHY
Year this degree conferred — Annee d obtention de ce grade
Name of Supervisor — Nom du directeur de these
)
DR. A. R. WEBSTER
FALL 19 83
^
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«•
Date
Signature
J u ly 12,
J".
1983
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THE PROPAGATION OF -MICROWAVES ON
IjINE-OF-SIGHT OVEftSEA PATHS
\
by
i
W an g-Leu ng I g n a t i u s Lam
F a c u lty o f E n g in ee rin g S cience
Subm itted i n p a r t i a l f u l f i l l m e n t
o f tlie r e q u ir e m e n ts f o r t h e d e g r e e o f
D octor o f P h ilo so p h y
/
F a c u lty o f G raduate S tu d ie s
The U n i v e r s i t y o f W e s t e r n O n t a r i o
London, O n t a r i o
A p r i l , 1983
,
■
\
©
W a n g - L e u n g . - I g n a t i u s Lam
198*3.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
The University of, Western Ontario
Faculty of Graduat* Studies
* i/
In ther interests o f facilitating research by others at this institution and elsewhere, I hereby
grant a licence to:
THE UNIVERSITY OF WESTERN ONTARIO
to make copies o f my thesis
THE PROPAGATION OF MICROWAVES ON LINE-OF-SIGHT OVERSEA PATHS
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V
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National Library o f Canada ,
f signature o f witness
Ju ly 1 2 , 1983
(date)
(signature o f student).
P h.D .
(degree)
E n g in e e rin g S cience
(department o f student)
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TH^UNIVERSITY. OF WESTERN' ONTARIO - FACULTY OF
‘ GRADUATE STUDIES
,'
♦
<3«
CERTIFICATE OF EXAMINATION
,
Exam ining Board
C h ief A dvisor
6
.,
A d v is o r y Committee
The t h e s i s T5y
W an g - L e u n g I g n a t i u s Lam
4
i
1
en titled
The P r o p a g a t i o n o f M i c r o w a v e s on
>
L in e - o f - s ig h t O versea P aths
i
is accepted in p a r t i a l f u lf illm e n t of th e
re q u ire m e n ts 'o f th e d egree of
D octor o f P h ilo so p h y
Date
,
” c h a ir m a n o f Exam ining Board
ii
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
/
^
I
ABSTRACT
o
The
Bay
p resents
of
a
Fundy,
h o stile
w ith
its
h u m id
environm ent
'V '
, m icrow ave d i g i t a l r a d i o
for
system s
fadingi s
the
of
d esig n ers.
operation'
to
thefre q u e n t
T herefore,
r a y £>ath c h a r a c t e r i s t i c s
value
to
system
and
clim ate,
the
due
o c c u rre n c e tjf m u l t i p a t h p r o p a g a t i o n .
kn o w le d g e * o f
m aritim e
of
a d etailed
during m u ltip a th
p ropagation
path
"
i
,
Two r a i c r b w a v e
propagation
experim ents
were
conducted
V
o n .sep arate
oversea
p a t h s a c r o s s t h e Bay o f
and
A, s w e e p
frequency
1981.
operated w ith
used.
The
a frequency
data
from
provide-
*
o ft the
received
to
system
1 0 . 5 . <SHz was
inform ation
ray(s%
am plitude,
a n g l e - o f - a r r i v a l , ..and
each
A d ig ital
ray.
9.5
1980
on
v arious
i
ch ara c te ristic s
radio
test
These ilic lu d e
relativ e
delay
•
t h e 1981 e x p e r i m e n t o n a n e s s e n t i a l l y
the
tim e
was a l s o c o n d ^ t e d
*
*■
in
m icrow ave, d ia g n o stic
sweep
co llected
Fundy
.of
during
»
id e n tic a l propagation
path.
The
resu lts
illu strate
.the
.
severe
v
fading
ad d itio n ,
from
these
activ ities
an g les-o f-arriv al,
observed
ire
These
. tim es, .
resu lts
are
presented
asso ciated
across
p resented
delay.
^p erform ance of th e d i g i t a l
.
are
p r o p a g a t i o n . m echanism s
'
* *
sta tistics
d istrib u tio n s^
experim ents
on
the
p ay
and
*
w ith
bay/*
In
am plitudes,
fade
related
radio.
iii
’
to
4
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
.depth
to
the
It
is
found t h a t most of
the
r e s u l t from t h e com bined e f f e c t s
th e sea
*
ray are
reflectio n .
discussed
roughness
of
a tm o s p h e ric l a y e r s and
The p r o p e r t i e s
in
d e ta il as
iv’
atm ospheric
and
P articu larly
severe fading a c t i v i t i e s
sig n ifican t
is
the
of ..th e s e s ’ re fle c te d
a fu n ctio n
of
sea
surface
y
refractiv e
in flu en ce
•
p ro p erties.
of
atm o sp h eric
•
l a y e r s on t h e r e f l e c t e d r a y .
T h e se l a y e r s 'h a v e t h e e f f e c t
e
/
of
substan tially
re fle c te d 'ra y
*,
•
in creasin g th e r e la tiv e
t o more t h a n
delay
10 n a n o s e c o n d s .
tjime o f t h e
A uxiliary
ray
p a t h s w i t h such lo n g d e la y tim e s ,, w hich a r e r a r e l y found i n
th e l i t e r a t u r e ,
d ig ital
h a v e s i g n i f i c a n t i m p a c t , on t h e o p e r a t i o n o f
0
ra d io system s,
frequency
d iv ersity
in p a r t i c u l a r ,
p ro tectio n
th e e f f e c t i v e n e s s of
schemes
are
much
when t h e s e l o n g d e l a y r a y p a t h s a r e p r e s e n t ' .
iv
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
reduced
kaitiWUEDG SHUTS
I . would
P rofessor
lllce
Alan
ex cellen t'
t o , e x p r e s s my S i n c e r e * g r a t i t u d e
to
’
■
r
‘ *
W e b s t e r , my t h e s i s a d v i s o r , ' f o r h i s
R'.
guidance.
experim ents
H is
effo rts
in
organising
the
and h i s a c t i v e ,in v o lv em en t i n t h e r e s e a r c h a r e
v e r y i^uch a p p r e c i a t e d .
~
c
Thanks
go
.
.
to
S r
for
M.P.
Hr.
P othier
for
’
d is c u s s io n s and
t h e e x t r a e f f o r t s beyond
*
I
d u t i e s j a t ’M.T.fc T d u r i n g t h e 1981 e x p e r i m e n t .
Many
thanks
also,
go - t o
enco u rag em en t and g r e a t h e l p
in
the
h is
M rs . M. M e ig h e n
the
typing;
f o r d r a w i n g some o f t h e d i a g r a m s ; a n d Mr. R . J .
useful
normal
for
her
Ms. S.- F r a n k
H aycock f o r
h i s h e lp d uring th e p r e p a r a tio n of th e ex p erim en ts.
0
*
"\
I would a l s o l i k e t o acknow ledge t h e f i n a n c i a l s u p p o r t '
p r o v i d e d by t h e C o m m u n i c a t i o n s R e s e a r c h C e n t r e , , a n d f o r t h e
♦
u s e o f v a r i o u s e q u i p m e n t a n d f a c i l i t i e s p r o v i d e d by t h e |
C entre
for
Radio
Science
«
d u rin g
The
close
9
c o o p e r a t i o n of M aritime, T e le g ra p h
<
‘
’
B ru n sw ic k - Telephone
d u rin g
the
*
app reciated .
t h e . work.
*
and
T e l e p h o n e - a n d New
>
‘*
experim ents
is
much
'
•
•
'
. .
,
»
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
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" ■•', **’-vv .
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♦
Page
•
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t •
CERTIFICATE OF EXAMINATION
, ...........................................
ABSTRACT . . ' . . . . ......................................
ACKNOWLEDGEMENTS .....................
. » ..........................
TABLE OF CONTENTS ............... ...............................
LIST OF T A B L E S ' . . . . * ......................
LIST OF FIGURES
...............
NOMENCLATURE .............................................................’. ...................................
4
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u
iii
v
vi
ix
x
xvi
*
CHAPTER 1 - INTRODUCTION ......................................
, 1 . 1 . B a c k g r o u n d .....................................
1 . 2 . O b j e c t i v e s a nd T h e s i s F o r m a t . . .......................... . . . s .
* *N
*
CHAPTER 2 - MICROWAVE PROPAGATION IN THE
TROPOSPHERE .....................
. . . . . . . ' ____
2 . 1 / T h e R e f r a c t i v e I n d e x i n t h e * T r o p o s p h e r e .............
• 2 . 2 . P r o p a g a t i o n i n an A t m o s p h e r e w i t h ? U n i f o r m
1
R efractiv ity G r a d ie n t
. . . . . ..................................
| , 2 . 3 . Ray - T r a c i f i g and t h e M o d i f i e d R e f r a c t i v e
I .
Index . . . i .
........................................................
2 . 4 . P r o p a g a t i o n i n an A t m o s p h e r e - w i t h N o n - u h i f o r m
..................................
>
.R e f r a c tiv ity G radient
2 . 4 . 1 . Anomalous P r o p a g a t i o n
..................
2 . 4 .2 . E f f e c t s of A tm ospheric L a y e r s
......
2 .4 .3 . M u ltip a th P ro p a g a tio n in a T u rb u le n t
A t m o s p h e r e ......................................................; . . . . .
2 . 5 . T e r r a i n E f f e c t s on R a d i o . W a v e P r o p a g a t i o n . . . 2 . 5 . 1 . P a t h C l e a r a n c e andv t h e F r e s n e l Zone . . .
2 . 5 . 2 . R e f l e c t i o n from T e r r a i a S t r u c t u r e s . . . .
1
1
.5
7
7
10
1
18
18
19
29
31
31
32'
CHAPTER .3
THE EXPERIMENTAL EQUIPMENT . . . y
t . . ..
36
. 3.1. in tro d u c tio n
....................................................
' 3 . 2 . ’T h e M i c r o w a v e D i a g n o s t i c S y s t e m
............................
36
*
3 . 2 . 1 . G e n e r a l D e s c r i p t i o n . . ' .............................................
36
3 .2 .2 . P r in c ip le of O peration
................................ * 37
3 . 2 . 3 . Equipm ent D e t a i l s ^
................. I ................
44
3 . 3 . T-he D a t a . A c q u i s i t i o n S y s t e m ...................................
48
3 . 3 . 1 . G e n e r a l D e s c r i p t i o n ...................................
48
3 . 3 . 2 1 S y s t e m C d n f i g u r a t i p n ...................................
.49
3 . 4 . The| D i g i t a l f i a d i x K / .
........................................
52
. 3 , 4 . 1 . t3&nef a l ^ f J e w r a i p t i o n
52
' 3 , 4 . 2 . E q u i p m e n t D e r a i l s ............................
53'
'%•
CHAPTER 4 - THE PROPAGATION EXPERIMENTS ...............
56
4.1. I n tr o d u c tio n .
» . . . , .......................................
56
4 . 2 . T h e P r o p a g a t i o n P a t h i n t h e 19 80 E x p e r i m e n t ' . .
594 . 3 . T h e P r o p a g a t i o f t P a t h i n t h e 1981 E x p e r i m e n t . .
67
.............................................
72
4 . 4 . Data A n a l y s i s
e,
4 . 4 . 1 . D a ta from th e P r o p a g a t io n E x p e rim e n ts .
72
vi
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
4 .4 .2 .
D a t a fro m t h e D i g i t a l R a d i o T e s t
............
80
' . CHAPTER 5 - MICROWAVE PROPAGATION ACROSS THE BAY OF
FUNDY — AYLESFORD TO O^PTER'LAKE ..................
82
5 . 1 . I n t r o d u c t i o n ............... » . . . , ...........................’
82
5 . 2 . G e n e r a l E x p e r i m e n t a l O b s e r v a t i o n s .......................
83
‘ 5 . 3 . P ro p a g a tio n During N o n -fad in g P e r io d s
86
5 . 3 . 1 . Ray A m p l i t u d e s and D e l a y T i m e s
. ‘ 86
5 . 3 . 2 . M ain Ray A n g l e - o f - A r r i v a l ............................ .'
.93
5 . 3 . 3 . R e f r a c t i v i t y G r a d i e n t V a r i a t i o n s .............
95
5 . 4 . The S e a R e f l e c t i o n .............
98
5 .4 .1 . R eflectio n C o efficien t
................... ' . . . .
98
101
5 . 4 . 2 . The R e f l e c t i n g A r e a ..............................
5 . 4 . 3 . E f f e c t s o f S e a S u r f a c e R o u g h n e s s .......... .'
101
5 .4 . 4 . ' D i f f u s e S c a t t e r i n g C o m p o n e n t " ......................
106
107
5 . 5 . P r o p a g a t i o n D u r i n g F a d i n g P e r i o d s ...........................
5 . 5 . 1 . R e s u l t s on Day 250................
107
5 . 5 . 2 . R e s u l t s qn Day 258 i .............................................
118
5 . 6 . Ray P a t h S t a t i s t i c s ................................
118
5 . 7 . Summary ............................................ i ................ ,....................
126
CHAPTER 6 - MICROWAVE PROPAGATION ACROSS THE BAY OF
FUNDY — OTTER LAKE TO NICTAUX SfXJTH ____
6 . 1 . I n t r o d u c t i o n ............. . . . . . . . . ...............................................
6 . 2 . G e n e r a l E x p e r i m e n t a l O b s e r v a t i o n s . . . . » ................
6 . 3 . P r o p a g a t i o n D u r i n g N o n - F a d i n g P e r i o d s ..................
6 . 4 . A n o m a lo u s P r o p a g a t i o n ..........................................................
6 . 5 . A t m o s p h e r i c L a y e r s ..............................
6 . 6 . Ray P a t h S t a t i s t i c s .................
6 . 7 . Summary .........................
128
128
129
132
141
147
188
160
CHAPTER 7 - THE STATISTICS OF SIGNAL FADING . . . . . . . . .
. 7-<l. I n t r o d u c t i o n . ..........................-............... .............................» . . .
7 . 2 . S i g n a l L e v e l D i s t r i b u t i o n s ..............................................
7 . 2 . 1 . S t a t i s t i c a l M o d e l s ............
7 .2 .2 . P rev io u s E x p erim ental F in d in g s . . . . . . . . .
7 . 3 . E x p e r i m e n t a l R e s u l t s on Fade D epth
- D i s t r i b u t i o n s ..............................................................................
7 .3 .1 . G eneral D escrip tio n s
......................................
• 7 . 3 . 2 - . S i g n a l F a d i n g S t a t i s t i c s ...............
7 . 3 . 3 v S i g n a l E n h a n c e m e n t S t a t i s t i c s ....................
7 . 3 . 4 . O t h e r A s p e c t s . t .....................
• 7 . 4 . Summary
.....................................
163;
16L
162
162
166
CHAPTER 8 - THE DIGITAL RADIO .’ .....................................................
8 . 1 . I n t r o d u c t i o n . . . . . . . . ..................................................
8 . 2 . M icc#wave D i g i t a l R a d i o S y s t e m s ............
8 . 2 . 1 . B a c k g r o u n d ...................................................■................
8 . 2 . 2 . P r o p a g a t i o n I m p a i r m e n t s on D i g i t a l
Radio S ystem s
........................................ . .
8 .2 * 3 . Space D i v e r s i t y Combining and
A daptive E q u a liz a tio n
....................................
179
179
180
180
v ii
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
167
167
168
172
175
177
182
187
*
•
:
"
mi
>
'
<
4
’ ’
«tr
P e rfo rm a n c e of D i g i t a l ’ R adio A c r o s s t h e
,, ’
B ay o f F u n d y . . . . . * ......................................... ^ ......................
8 . 3 . 1 . System R e l i a b i l i t y O b j e c t i v e s
.............
8 . , 3 . 2 . E x p e r i m e n t a l 1 R e s u l t s ............................................
% . 3 . 3 . S t a t i s t i c a l R e s u l t s ..............................................
,
8 . 4 . Summary
8 .3 .
^
188
188
189
197
199
♦
CHAPTER 9 -
SUMMARY AND CONCLUSIONS
..............................,. . .
201
APPENDIX 1.
D im e n sio n s o £ the f i r s t F r e s n e l E l l i p s e
on t h e g r o u n q f o r S p e c u l a r R e f l e c t i o n
on LOS M ic r o w a v e L i n k s
..............................
205
APPENDIX 2 .
Summary o f D i a g n o s t i c S y s t e m P a r a m e t e r s .
209
APPENDIX 3 .
D e t a i l s o f th e Data A c q u i s i t i o n System
210
APPENDIX 4 .
P aram eters of the P ro p ag atio n P aths
..
.....
213
i
*
APPENDIX 5 . A n a l y s i s o f Sw ee p F r e q u e n c y A m p l i t u d e
R e c o r d s ...............
♦
"
2-14
*
APPENDIX 6 . Summary o f R e s u l t s o f t h e 1980 1
..........................................................
E xperim ent
219
APPENDIX 7 . S u n m a r y o f R e s u l t s o f
„ E x p erim en t
225
*
}
*
t h e 1981
.........................................
REFERElfcES
..................................... . . . . . . . .....................
VITA . . . * . .......................................................
‘
♦
♦
✓
H1
.
•
*
f
’
*
v iii ^
»
*
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
244
250
LIST
Tabl-e
2.1
5.1
5.2
5.3
5.4
TABLES
. D escription
* .
.Page
'
'
"
.
Some r e p o r t e d v a l u e s o f d u c t p a r a m e t e r s
in c lu d in g h e ig h t of occurrence h , duct
s t r e n g t h AN r and* anomaly* t h i c k n e s s Ah
E x p e rim e n ta l and p r e d i c t e d ra y p a th
c h a r a c t e r i s t i c s f o r t h e 1980
' non-fading d ata
'
W o r ld M e t e o r o l o g i c a l O r g a n i z a t i o n
S e a - s ta te Scale
[37]
..
*
23
91.
(WMO)
^
104
P e r c e n t a g e o c c u r r e n c e o f wave h e i g h t s f o r
t h e ocean a s a w hole
[37]
104
Comparison o f e x p e r i m e n t a l r e s u l t s and ra £ \
path p aram eters e s tim a te d w ith ray tr a c in g
f q r a l a y e r p r e s e n t below t h e a n t e n n a s
115
ix
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
>
*
\
*
-
*
*
#
4
r
L I S T OF^flGORES
*
D escription
fig u re
*
»
i
P age
V a ria tio n of r e f r a c t i v i t y N w ith tem perature
t and r e l a t i v e r l s j g n i d i t y H a t a p r e s s u r e of
1000 mb.
2.1
9
•u
*
; M o d e ls f o r r e p r e s e n t i n g r a y p a t h p r o p a g a t i n g
oyer e a rth su rfa c e
•
'
The Ray T r a c i n g g e o m e t r y
2.2
»
I
n
t
2.3
'
t
w
The M- artd N- p r o f i l e s f o r
elevated duct
2.4
12 .
-6
V
an i d e a l i z e d ,
20
*
R e p r e s e n t a t i v e r a y s la u n c h e d from v a r i o u s
p o i n t s r e l a t i v e t o a, p r o p a g a t i o n d u c t
2.5
„
25
-
2.6
>
*
P ropagation i n , t h e
(a) r a y s l a u n c h e d
(b) r a y s l a u n c h e d
(c) r a y s l a u n c h e d
‘
>
2.7
D iffra c tio n lo s s versus te r r a in
3.1
The p h a s e -s w e p t i n t e r f e r o m e t e r
3.2
28
38'
[7|r
-
41
> A m p l^ u d e c h a r a c t e r i s t i c s ,o f . t h e r e s u l t a n t of
two s i g n a l s w i t h r e l a t i v e t i m e d e l a y o f At
’
3.4
*
33
clearance
V e c t o r a d d i t i o n o f two s i g n a l s w i t h a
. r e l a t i v e t i m e d e l a y o f At
‘
3.3 *
‘
presence of a d u c t:'
from above t h e d u c t
from w i t h i n t h e d u c t
from below t h e d u c t
1
41
»
S y n t h e s i z e d sw eep f r e q u e n c y a m p l i t u d e and
p h a s e r e c o r d f o r tw o r e c e i v e d r a y p a t h s
43
B lock d iag ram of t h e D i a g n o s t i c System .
tran sm itter
^
r
45
B lock diagram of t h e D i a g n o s t i c System ’
receiv er
*
.
4d
C o n f i g u r a t i o n of t h e D ata A c q u i s i t i o n
System
50
B lock d iag ram of t h e D i g i t a l R adio
R eceiver
>
1 -
54
*
3*E>
3.6
t
3.7
-
t
.
■<
3 .8
.
4
The p r o p a g a t i o n p a t h s a c r o s s t h e Bay o f
Fundy
4.1
>
*
*
«
i
X
‘N
•*
.
''
. ■ ''
r v
R e p r o d u c e d with p e r m i s s io n of t h e co p y rig h t o w n e r. F u r th e r r e p r o d u c tio n prohibited w ith o u t p e r m is s io n .
•
58 -
4 .2
P ath p r o f i l e fo r
p ro p ag atio n path
4.a
th e A ylesford
*
- O t t e r Lake
60.
Seasonal p r o b a b ility d i s t r i b u t i o n of
ground-based r e f r a c t i v i t y g ra d ie n ts fo r
(a) P o r t l a n d , M e., and
(b) S a b l e
*
I s l a n d , NS
[3]
'
>.
62
..
4.4
S ea'so n al b e h a v i o u r o f t h e s u r f a c e
r e f r a c t i v i t y f o r : ; (a) P o r t l a n d , M e., and
(b) S a b l e I s l a n d , N S *
[3]
•
4.5
63
Ray T r a c i n g o n A y l e s f o r d - O t t e r L a k e p a t h
for th re e re p re s e n ta tiv e v alu es of th e
re fr a c tiv ity g rad ien t
,
65'
y
.
.
1 -■
.
Ray p a t h c h a r a c t e r i s t i c s f o r A y l e s f o r d O t t e r L a k e p a t h u n d e r c o n d i t i o n s o f u n i f o r m ««. •
r e fr a c tiv ity g rad ien t
' 66
*
4.6
4.7
^
P a th p r o f i l e f o r t h e O t t e r Lake S outh p r o p a g a t i o n 'p a t h
’
4.8
N ictaux
Ray T r a c i n g o n t h e O t t e r L a k e - N i c t a u x
S outh p ath fo r th r e e r e p r e s e n ta tiv e v a lu e s
of th e r e f r a c t i v i t y g ra d ie n t
,
468
* '
70
p
»
4.9
4.10
j
Ray p a t h c h a r a c t e r i s t i c s f o r t h e O t t e r L a k e N ictau x S outh p a th under c o n d i t i o n s of
uniform r e f r a c t i v i t y g r a d i e n t
71
E stim a tio n of ray a m p litu d e s u sin g th e
a n a ly s is ro u tin e ; th e v e r t i c a l b a rs a re th e
e rro r 'b o u n d s of th e e s tim a te d a m p litu d e s
75
%
4.11
E f f e c t s of* s h o r t d e l a y r a y p a t h s o n t h e
sweep f re q u e n c y r e c o r d s ; t h e broken, l i n e s
show t h e i d e a l p h a s e r e c o r d s i f t h e . s h o r t
d elay ray p a th i s a b s e n t
7.7
‘
«
4.12
I
5.1
5 .2
5.i
S p u rio u s v a r i a t i o n s i n e s t i m a t e d m ain ra y
AOA d u e t o s h o r t d e l a y s e c o n d ^ r a y p a t h
79
■Time c h a r t o f s e l e c t e d e x p e r i m e n t a l ~
o b s e r v a t i o n s f o r t h e 1980 e x p e r i m e n t
85
E xperim ental (d o tte d ) and s y n th e s iz e d d a ta
r e c o r d a t 1 2 : 0 0 : 0 1 ADT o n Day 2 £ 5
87
Ray p a t h c h a r a c t e r i s t i c s o h a n o n - f a d i n g
day (295) i n t h e 1980 e x p e r i m e n t
88
xx
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
r'
5.4
*
5.5
5.6
D i s t r i b u t i o n s o f th e ra y a m p litu d e s and
r e l a t i v e d e l a y t i m e f o r t h e 1980 n o n - f a d i n g
data
»
90
D i s t r i b u t i o n o f t h e j n a i n r a y AOA f o r
1980 n o n - f a d i n g d a t a
94
the
V a r i a t i o n s i n r a y p a t h c h a r a c t e r i s t i c s due
to a suspected v a r ia tio n in th e o v e ra ll
r e fr a c tiv ity g radient
T-
5.7
S '*
5.8
5.9
5.10
sin
5.12
5.13
5.14
I-
/^97
*
The m a g n i t u d e [R0 | a n d p h a s e ^ o f t h e
r e f l e c t i o n c o e f f i c i e n t o f a v e r y smooth
e /e
8 0 , o = 4 mho/m.
[24]
sea.
100
The s c a t t e r i n g c o e f f i c i e n t * a s a f u n c t i o n o f
Ah f o r d i f f e r e n t v a l u e s o f y a t a f r e q u e n c y
o f 10 GHz
103
Ray p a t h c h a r a c t e r i s t i c s on a f a d i n g d a y
(2 50) i n t h e 1980 e x p e r i m e n t
108
E x p erim en tal ( d o tte d ) and s y n th e s iz e d d a ta
r e c o r d a t 1 8 : 0 4 : 5 6 ADT on Day 250,,
111
E xp erim en tal (d o tte d ) and s y n th e s iz e d d a ta
r e c o r d a t 2 1 : 0 0 : 0 6 ADT on Day 250
112
P r o p a g a t i o n on t h e A y l e s f o r d - O t t e r La ke
p a t h when a n a t m o s p h e r i c l a y e r i s p r e s e n t
below t h e a n t e n n a s
114
T e m p e ratu re and*wind s p e e d o b s e rv e d a t
S a i n t J o h n A i r p o r t on Day 250
117
Ray p a t h c h a r a c t e r i s t i c s on a f a d i n g d a y
( 2 5 8 ) ^ i n t h e 19 80 e x p e r i m e n t
5.15
5.16
T em perature and w ind s p eed o b s e rv e d a t
S a i n t J o h n A i r p o r t on D ays 257 a n d 258
120
D i s t r i b u t i o n s o f th e ra y a m p litu d e s and
r e l a t i v e d e l a y t i m e f o r t h e 1980 f a d i n g d a t a
122
9
5.17
*
D i s t r i b u t i o n s of th e r e l a t i v e d elay tim e
(se c o n d ra y r e l a t i v e t o t h e m ain ra y ) f o r
t h e 1980 n o n - f a d i n g a n d f a d i n g d a t a p l o t t e d
o n N orm al P r o b a b i l i t y p a p e r
r
5.18
119
y
k '
i
123
D is tr ib u tio n s of ray am plitudes fo r th e
'
*
1980 n o n - f a d i n g a n d f a d i n g d a t a p l o t t e d on /
N orm al P r o b a b i l i t y p a p e r
124
x ii
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
6.1
Tim e c h a r t o f e x p e r i m e n t a l o b s e r v a t i o n s f o r
t h e 19 8 1 e x p e r i m e n t
6 .2
Summary o f 198 1 e x p e r i m e n t a l r e s u l t s o n a
p e r day b a s i s .
The a r r o w s m a r k t h r e e
d i s t i n c t p e r io d s w ith heavy fa d in g
*
6.3
6.4
131
/
Ray p a t h c h a r a c t e r i s t i c s o n a n o n - f a d i n g
d a y ( 2 1 9 ) i n t h e 19 8 1 e x p e r i m e n t
133
S purious v a r i a t i o n s in th e phase re c o rd
s i Ope c a u s e d b y t h e p r e s e n c e o f a s h o r t
d e la y ra y w ith a slow ly v a ry in g d e la y tim e
135
E x p e rim e n ta l ( d o tte d ) and s y n t h e s i z e d d a ta
r e c o r d a t 0 0 : 0 0 : 0 5 ADT o n Day 2 1 9
136
*
6.5
D i s t r i b u t i o n s of ± h e ray a m p litu d e s and
r e l a t i v e d e l a y t i j p e f o r t h e 198 1
non-fading d ata
*
i
‘
D i s t r i b u t i o n o f t h e m a i n r a y AOA f o r t h e
19 8 1 n o n - f a d i n g d a t a
6.6
6.7
6 .$
6.9
6.10
*
130
137
.
140
Ray p a t h c h a r a c t e r i s t i c s on a f a d i n g d a y
(225) i n t h e 1981 e x p e r i m e n t
142
Ray p a t h c h a r a c t e r i s t i c s on t h e w o r s t f a d i n g
d a y ( 2 4 2 ) i n t h e 19 81 e x p e r i m e n t
144
E x p erim en tal (d o tte d ) and s y n th e s iz e d d a ta
r e c o r d a t 1 0 ^ , 0 4 : 5 2 ADT on Day 242
146
r
6.11
•
P r o p a g a t i o n on t h e O t t e r L a k e - N i c t a u x
S o u t h p a t h when a n a t m o s p h e r i c l a y e r i s
p r e s e n t a t v a r i o u s h e i g h t s : , , (a) l o w - le v e l
layer
(b) m i d - l e v e l l a y e r ‘ ( c ) h i g h l e v e l
layer*
\
6 .12
E f f e c t s o f l a y e r h e i g h t v a r i a t i o n s on r a y
p a t h c h a r a c t e r i s t i c s f o r t h e O t t e r Lake N ic ts a u x S o u t h p a t h .
R .. . . re fle c te d ray,
NM.. . . N o r t h M ounta jw ^ [44]
6.13
* The maximum r e l a t i v e d e l a y o f t h e r e f l e c t e d
r a y ' " c a u s e d by a s i n g l e l a y e r w i t h
s t r e n g t h An
, 4,
148
151
154
t
6.14
6*15
'
D i s t r i b u t i o n s of th e ray a m p litu d e s and
r e l a t i v e d e l a y t i m e f o r t h e 1 9 8 1 vf a d i n g d a t a
156
D i s t r i b u t i o n of th e r e l a t i v e d e la y tim e of
t h e r e f l e c t e d ray, i n t h e 19 8 1 e x p e r i m e n t
p l o t t e d on N o r m a l P r o b a b i l i t y p a p e r
157
X lll
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
6.16
7.1
7.2
7.3
7.4
7.5
8.1
D i s tr ib u tio n s of th e ray am p litu d es j n th e '
1981 e x p e r i m e n t p l o t t e d on N or mal
P r o b a b ility paper
159
Fade d e p th d i s t r i b u t i o n s ^ f o r t h e n o n - f a d i n g
d a t a , f a d in g d a t a , and t h e t o t a l d a t a b a s e s
i n t h e 1980 e x p e r i m e n t
169
Fade d e p t h d i s t r i b u t i o n s f o r t h e n o n - f a d i n g
d a t a , f a d i n g d a t a , and t h e t o t a l d a t a b a s e s
i n t h e 198 1 e x p e r i m e n t
171
D i s t r i b u t i o n s of s ig n a l enhancement fo r th e
19lJ0 e x p e r i m e n t
173
D i s t r i b u t i o n s of s i g n a l ’ enhancement fo r th e
1981 e x p e r i m e n t
£sl
174
S i g n a l l e v e l d i s t r i b u t i o n s f o r t h e 1980 a n d
1981 e x p e r i m e n t s p l o t t e d on R a y l e i g h
C oordinates
176
P ( e ) p e r f o r m a n c e o f M -ar y PSK, QAM, QPR, a n d
M-ary-APR c o h e r e n t s y s t e m s .
The rms C/N i s
s p e c if ie d in th e d o u b le -sid e d N yquist
bandw idth
[34]
183
+
8.2
1
H ig h -sp e e d d i g i t a l r a d i o IF d i s p e r s i v e f a d e
s i m u l a t i o n s , At® 6 . 3 n s , f 0 = - 1 9 . 8 MHz
r e l a t i v e t o t h e c e n t r e of t h e c h a n n e l where
f c i s th e frequency a t th e notch
[56]
184
<
8*.3
8.4
E f f e c t o f l o n g r e l a t i v e d e l a y t i m e on .
d i g i t a l ra d io perform ance
192
D iagram ^to i l l u s t r a t e t h e p r o b a b i l i t y t h a t
a p a r t i c u l a r r a d i o c h a n n e l w i l l c o n t a i n an
i n - b a n d n u l l , g i v e n t h e c o n d i t i o n t h a t two
ray p a th s a re receiv ed
193
A-
8.5
8.6
*'
8.7
8.8
P r o b a b i l i t y of in -b a n d n u l l s V e rsu s
r e l a t i v e d e la y of seaond ray
195
N ull s e p a r a t i o n v e r s u s r e l a t i v e d e la y of
second ray
195
O ccurrence
of i n - b a n d n u l l s on a d j a c e n t
r a d i o c h a n n e l s w i t h b a n d w i d t h s o f 4 0 'MHz
196
Delay tim e
d i s t r i b u t i o n d u rin g p e rio d s
when t h e d i g i t a l r a d i o s u f f e r e d
im pairm ent#,
xiv
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
.1 9 8
8.9
A m plitude d i s t r i b u t i o n d u r in g p e r io d s 'w h e n
th e d i g i t a l rad io su ffe re d im p airm en ts'
A l.l
The F r e s n e l E l l i p s e i n t h e b a s e o f s p e c u l a r
r e f l e c t i o n on LOS p a t h s
A5.1
The v e c t o r a d d i t i o n o f two s i g n a l s w i t h ' a
r e l a t i v e t i m e d e l a y o f At
A5.2
A m plitude c h a r a c t e r i s t i c s o f th e
r e s u l t a n t o f tw o s i g n a l s w i t h r e l a t i v e
tim e d elay of At
*
1
A5.3
A'
S cale f a c to r s re q u ire d to produce c o r r e c t
e s t i m a t e s of. r a y a m p l i t u d e s
•
XV
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
£♦
NOHEHCLATURE
earth
radius
e ffe c tiv e e arth radius,
/ s/H z
b i t s per second per h e r tz
v e l o c i t y of l i g h t
p a r t i a l p re s s u re of w ater vapour
s a t u r a t i o n vapour p r e s s u r e of w ater
f
frequency
h
heig h t
h0
‘ lay er h eight
he
duct thickness
h^
layer
h {4
maximum wave h e i g h t
j
v^T
k
thickness
"*■
,_ b asic . r e f r a c t i v i t y
gradient
*
1
*
p h y s ic a l path len g th
*
mb
100,P ascal
n
refractiv e
t
I*
.
i
index
tem perature
■**
t(L )
a v e r a g e d u r a t i o n o f facies c o r r e s p o n d in g
to lev el L
Al
m ain ray
A2
second ray
ADC
analog to d i g i t a l co n v e rte r
( s t r o n g e s t ray)
(weaker ra y )
ADT
. A t l a n t i c D a y l i g h t Time
AGO
au tom atic g ain c o n tro l
AOA
an g le-o f-arriv al
am plitude
am plitude
xvi
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i
AOA* s
an g les-of-arriyal*
AOAI
m ain r a y a n g l e - o f - a r r i v a l d e r i v e d from
i n t e r c e p t of phase r e c o rd
AOAS
, rfain r a y a n g l e - o f - a r r i v a l d e r i v e d from
- slo p e of phase re c o rd
BER
,
.
*b it-erro r-ra te
*
*■
-
BERT
BPF
b it-erro r-ra te te st
t
band-pass f i l t e r
BPSK
b in a r y phase s h i f t keying
CPU
c e n tra l processing u n it
CCIR
'
set
I n t e r n a t i o n a l ^ a d i o C o n s u l t a t i v e Committee
D
divergence c o e f f i c i e n t
E'
f i e l d strength^
/ ,
"EPROM
■*
•
'
e r a s a b l e - p r o g r a m a b l e r e a d only'm em o ry
rad ius of the f i r s t
F r e s n e l Zone
Fn
U
r a d i u s\ o f t h e n - t h F r e s n e l Zone
FM
frequency m odulation
FSK
frequency s h i f t keying
H
r e l a t i v e hum idity,
IF
in te rm e d ia te frequency
I/O
in p u t-o u tp u t
K
K ilo-byte
K
e ffe c tiv e earth radius facto r
L
phase path le n g th
L
sp e c ifie d sig n al le v e l
LOS
lin e-o f-sig h t
%
.M '
M b/s
•
^
£j*r*
/ rt
•
equal
to
e/es
*
m o d ified r e f r a c t i v e index
M e g a b its per second
,x v u
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MSL
mean s e a l e v e l
M.T.& T
M a r i t i m e T e l e g r a p h a n d T e l e p h o n e Company
N
refractiv ity
N{L)
number o f f a d e s c o r r e s p o n d i n g t o l e v e l L
%
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N0
ground’re f-ra c tiv ity
J
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NU,
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a
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p o w er d e n s i t y
.*
p r o b a b i l i t y ’, o f i n - b a n d n u l l
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P
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<
Pn
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u n its of 1refractiv ity "
y
w
pressure
V
,
e r r o r p r o b a b i l i t y r same a s BER
PCM
pulbe-jpoded m o d u l a ti o n
PSK
phase s h i f t keying
QAM
q u a d ra tu re am plitude m odulation
QPR
quadrature p a r t ia l
R
reflectio n , c o e ffic ie n t
re fle c tio n c o e ffic ie n t for d iffu se
.
r a n d o m - a c c e s s memory
RP
ra d io frequency
t
RX
•
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’
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a b s o lu te te m p e ra tu re in K elvin
TCTS
Trans-Canada Telephone Systfm
tran sm itter
*
*
T
TTY
component
re c e iv e r or re c e iv in g antenna
,
- TX
,
r e f l e c t i o n c o e f f i c i e n t f o r s p e c u l a r component
-
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response
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r e f l e c t i o n c o e f f i c i e n t of p e r f e c tly
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R0
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,
p ro b ab ility ,
'
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•
or t r a n s m i t t i n g an ten n a.
telety p e
n
x y iii
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«
TWT
, trav ellin g -w av ey tu b e* am p lifier
•
'
.
s i g n a l levefl
t
V
»*
*
'3
*
.
a
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X-band
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( Y t t r i u m - I r b n - G a r n e t ) - t u n e d Gunn
dio£e o s c i l l a t o r
•
' .
• '
«
9
ray path angle r e l a t i v e to lo c a l h o r iz o n ta l
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p h y s ic a l path le n g th increm ent
•
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phase j? a t h ‘len g ttT increm ent >
r e l a t i v e phase
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•
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s c a tte rin g c o e f fic ie n t for
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th e specular
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grazing an g le
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c ritic a l
c
earth
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w avelength
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r e l a t i v e tim e d e la y b e tw e e n
1
•
,
*
*
layer
'
•
xix
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
s
•
C hapter 1
,
1.1
INTRODUCTION
Background
"
^
.
•’
*
. The h i s t o r y o f
r a d i p c o m m u n ic a tio n s, d a t e s back to' t h e
*.
‘
M arconi
first
succeeded in tr a n s m i ttin g
•
year
1896
when
'
te le g r a p h m e ss a g e s 'a c ro ss
years,
X
t h e E n g l i s h C h a n n e l by r a d i o .
*
subsequent
*
*
In .
»
L * '*
Advances in r a d io
*
technology r e s u l te d ' ip 4
.th e
use
or
com m unication
p rogressively
purposes.
By
higher
the
frequencies
for
early
195Q*s, m icrow ave
■>
d istance
telephone
«•
r a d i o s were u sed c p m l h e r c i a l ly in
netw orks,
long
i n N o rth A m e ric a . . Accompanying t h e s e a d v a n c e s
.
irt
»
..
tra n sm iss io n technology
were
developm ents
in
m odulation .
t
schemes
from
sin g le
channel
A m plitude
M odulation
to
’
m u ltic h a n n e l Frequency' M odulation te c h n iq u e s , r e s u ltin g '
in
*
i
*
*
m ore e f f i c i e n t
sp ectru m u t i l i z a t i o n s . * These te c h n o lo g ie s
.
4*
'
St
provided th e b a s is
for
telecom m unication
netw orks
•last d e c a d e .
th e .,
.
Iri-response to
\
of
t h e i n c r e a s i n g demands f o r
'
info rm atio n .
,
-
e x c h a n g e / ^ in. t h e m o d e r n s o c i . e t y , f u n d a m e n t a l c h a n g e s - i n t h e ’
C . •' 6
.
■
:'
•
s t r u c t u r e " o f t h e ' t e l e p h o n e sys. te m a r e c u r r e n t l y h e i n g : made '
*
*
w orldw ide.
D ig ita l tra n sm issio n system s, because of t h e i r '
cost
ad v an tag es,-
in terco n n ectio n
fle x ib ility
■»
and e x p a n s i o n ,
in
m u ltip lex in g ,
ease
of
<.
‘
and c o n s i s t e n t t r a n s m i s s i o n
q u a l i t y , u n d e r n d i s y s i t u a t i o n s 9, a r e r e p l a c i n g
conventional
1
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
(
analog
system s
At ' the
as
present
.the b a c k b o n e o f t h e t e l e p h o n e n e t w o r k .
tim e,
microwave
d ig ital
radio
system s
K
>
o p e r a t i n g *' i n
use.
the
2 , 6 , 8 , and 11 GHz b a n d s a r e i n common
I n t h e C a n a d i a n 8 GHz common c a r r i e r , f r e q u e n c y
»
the
band,
*
allocated
channel
bandw idths
are* .40 MHz.
s y s t e m s o p e r a t i n g "in t h i s b a n d p r o v i . d e s i g n a l l i n g
a ^ jro x im ately
90 M b/s
' ■
or
*
T ypical
rates
of
th e *equivalerit o f a p p ro x im a te ly
v'
1300 v o i c e c h a n n e l s , .
The i m p l e m e n ta tip n ; o f microwave d i g i t a l - r a d i o
presents
new * c h a l l e n g e s
requirem ents
*
/
system s
are
’t o t h e r a d i o p a t h d e s i g n e r .
'' a n d ' b e h a v i o u r ° o f ‘ W id e b a n d
’
system ?
,
- V
sig n ifican tly
d i f f e r e n t / from
d ig ital
radio
thos^
o f the
c o n v e n t i o n a l , narrowband ~FM 'anal’dg t ^ d i o p . ' . D i g i t a l r a d i o s ,
because
of
t h e m o d u l a t i o n s c h e m e s an d t h e w i d e b a n d w i d t h ,
*•
are p a r tic u la r l y
susceptib le
to th e
i
s e le c tiv e *m u ltipath
group
delay
and
efffects
of
frequency
»
fading,
d isto rtio n s. t
synchronization
»
fram ing
nam ely,
i n - b a n d a m p l i t u d e and
F urtherm ore,
purposes;
for
a
proper
pulse s tu f f in g
-c #
technique
is
. u su ally
e m p lo y e d '
in.
d ig ital
radios.
V
C onsequently,
bandw idth
*
the
the
radio
is
■*
alw ays
operating
in d e p e n d e n t o f th e a c t u a l amount
system .
of
Since
full*
loading
on
On t h e o t h e r h a n d ,, t h e o p e r a t i n g b a n d w i d t h ' o f
a n a n a l o g 'FM r a d i o i s d i r e c t l y p r o p o r t i o n a l t o
load.
at
severe
m u ltip a th ’ fading
the
/
system
o c c u r s fiore o f t e n
A *
during
loading
t h e n i g h t and
in
is u su ally lig h t,
the
early
its effects
m orning
w hen
are le s s
system
d etrim en tal
t o t h e o p e r a t i o n o f c o n v e n t i o n a l analog, r a d i o s y s te m s .
i
)
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
The a b o v e p r o b l e m s a r e
perform ance
stan d ard s
d ig ita l rad io s.'
sp ecified
by
For,
further
th at
co m pounded by t h e
/
r e g u la te - the
exam ple,
®
one
of
high
operatio n
the
of
requirem ents
**
th e" T ra n s -C a n a d a T e le p h o n e System f o r
8 GHz
*
d i g i t a l radio
is
an a v a i l a b i l i t y o f .
defined
a
hypo th etical
for
6560 km.
i
Whten s c a l e d
m icrow ave
radio
t o wa
to ta l
outage
ty p ical
tim e o f
of
th e
tim e,
c i r c u i t of len g th
lin e-o f-sig h t
50 km, t h e
T his is
(LOS)
av ailab ility
is
e q u i v a l e n t to an a l l o w a b l e
4S7 s jo e r - y e a r
average of 0.13 s p er day.
9
reference
lin k of length
99.99985 % o f th e tim e .
9 9 .9 8 %
( tw o way o u t a g e )
O u tag es due t o
both
or- an
equipm ent
4
-
failu res
and p r o p a g a t i o n i m p a i r m e n t s ' a r e i n c l u d e d and t h e s e
4
•
a r e ’ u su ally
t r e a t e d w ith eq u al w eig h t.
*
Th e
ch aracteristic§
terrestrial
of
lin e-o f-sig h t
featu res
the
o f «*%he
common c a u s e s o f s i g n a l f a d i n g
to
th e " lin e -o f-s ig h t path ,
m ultip ath propagation.
received
m icrowave
the r e f r a c t i v e p r o p e r t ie s o f
topog rap h ical
the
link
sig n al
is
atm osphere
on ^ t h e
terrain .
are d i f f r a c t i o n
•
*
*
may
u su ally
the
propagation
be
r e d u c e d o r a v o i d e d by a c a r e f u l d e s i g n o f
p ath .
Fading
m u ltipath
e f f e c t s , . ' how ever,
atm ospheric
'c o n d itio n s ,
propagation
and
d i f f r a c t i o n * fading
»
G enerally
The
by o b s t a c l e s
a b s o r p t i o n / b y hydroirfeteors,
The e f f e c t s o f
a'
d e p e n d e n t on
and
in terv en in g
on
%
due
are
to
absorption
u su ally
frequency,
a nd
and
dependent
path
on
len g th .
s p e a k i n g , a t f r e q u e n c i e s b e l o w 10 GHz, m u l t i p a t h
is
the
predom inant
cause
of
severe
f a d i n g on t e r r e s t r i a l m i c r o w a v e l i n k s .
«
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
sig n al
F a d in g due t o m u l t i p a t h e f f e c t s
in terferen ce
betw een
au x iliary
rays
d ifferen t
p ath s.
the
th at
d irect
reach
o c c u rs 'a s
ray
the
and
a resu lt
one
receiving
of
or
more
antenna
via
*
ground
reflectio n
reflectio n s
frequency
on
These
or
from
sele ctiv e
r a y s may° a r i s e
anom alous
lay ers.
nature of m u ltip a th
High b i t - e f r o r - r a t e s
even
from
atm ospheric
w ideband d i g i t a l
effects
au x iliary
from a
refractio n
and
Because . o f
the
its
effects
ra d io system s a re p a r t i c u l a r l y
severe.
may
r e s u l t from
when , t h e
fading,
in-band
average s ig n a l le v e l
d isto rtio n
i s w e ll above
-
♦
th resh o ld .
the receiv er
Pes p a r t
of the p r e s e n t
propagation
in v estig atio n ,
experim fents
two
were - p e r f o r m e d
m icrow ave
. on
sep arate
/*
lin e-o f-sig h t,
1980
a nd
oversea paths across
1981.
P rio r
resu lts
on
the '.p a th
of
Fundy
by
the
local*
in
of the te st- in d ic a te d
a
telephone
O s e d i n t h e 1980 e x p e r i m e n t .
The
t h a t th e perform ance , of
.
the
«■
d ig ital
radio in s ta lle d
‘
across
t h e b a y was u n a c c e p t a b l e d u e
r
'
t o unknowh p r o p a g a t i o n e f f e c t s .
were
Bay
t o . th e p r o p a g a t i o n e x p e r i m e n t s ,
d i g i t a l r a d i o t e s t was c o n d u c t e d
com panies
the
'
'
The -e x p e rim e n ts
p e r f o r m e d w i t h t h e a im o f
id en tify in g
th erefo re
the p r o p a g a tio n
m e c h a n i s m s t h a t a r e a s s o c i a t e d w i t h o u t a g e s on t h e
rad io .
In both e x p e rim e n ts,
d ig ital
s w eep f r e q u e n c y r e c o r d s o f
the
*
a m p l i t u d e an d p h a s e
spaced
antennas)
(relativ e
of
Subsequent a n a ly sis - of
estim ates
£
/
of
•
*.
the
■
the
p h a s e b e t w e e n two
received
th ese
am plitudes,
■
v ertic ally
s i g n a l were g a t h e r e d .
s w eep
records
then
gives
a n g l e s - o f - a r r i v a l , * and t h e
'
R e p r o d u c e d with p e r m i s s io n of t h e co p y rig h t o w n e r. F u r th e r r e p r o d u c tio n prohibited w ith o u t p e r m is s io n .
relativ e
delay
of
the
ad d itio n ,
a d ig ital
the
experim ent,
1981
in d iv id u al
r e c e iv e c ^ raV (s).
r a d i o was o p e r a t e d s i m u l t a n e o u s l y w i t h
p roviding
inform ation
C
\^on/
the
*
perform ance
of
such
a
system
under v a r io u s p r o p a g a tio n
co n d itio n s.
1.2
O b j e c t i v e s and T h e s i s F o r m a t
T h e main o b j e c t i v e o f
b etter
p ictu re
the
proposed.
respect
of
of
the
perform ance
fe
provide ' a
of
Fundy.
are a ls o
alw ays
P ossible
examined
of the d i g i t a l
radio
outages
is
not attem pted,
are
attain ed .
However,
c o n t r i b u t i o n i s made t o t h e body
w ith.-the p r o p a g a tio n of
o'f.
nor
discussed.
are
,it
w ith
r a d i o and t h e
th e * complex naturiT 'O f th e s u b j e c t ,
s e t of explanations
.resu lts
to
£3me>pf t h e o b s e r v e d f a d i n g p h e n o m e n a a r e
e v e n ts t h a t led to d i g i t a l
- Because
t h e Bay
The p r o p a g a t i o n r e s u l t s
tp
is
o f th e m echanisms t h a t a r e a s s o c i a t e d w i t h
m icrow ave p r o p a g a t i o n a c r o s s
ex planations
th esis
is
a com plete
co n clu siv e
hoped t h a t a
K now ledge
associated
r a d i o wa ves t h r o u g h t h e a t m o s p h e r e .
JWith t h e a b o v e o b j e c t i v e s
in m ind, t h e
thesis „ s ta rts
w ith a d i s c u s s i o n o f b a s i c microwave p r o p a g a t i o n m echanisms
in th e tr o p o s p h e r e
of
*
i
in C hapter 2 , -w ith d e s c r i p t i o n s of
X .j
some
t h e p a r a m e t e r s and n o t a t i o n s t h a t a r e u s e d i n s u b s e q u e n t
ch ap ters.
C hapter 3
The
experim ental
together
equipm ent
is .'d e s c rib e d
in
w i t h a s e c £ i o i y on t h e c o n f i g u r a t i o n o f
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
'l
th e
d ig ita l
co n tain s
rad io
a
ex p erim en ts
Fundy.
and t h e
u n ce rta in tie s
ex p erim en ts
in
observed
5'
th e
8.
are
p resen ted
s ta tis tic a l
th e
The
and
ex p erim en ts
-~©f
in C h a p te rs
to
4
p ro p ag atio n
th e
th e
Bay
of
asso ciated
d iscu ssed .
resu lts
offered
r.ay p a t h
are
C h ap ter
th e
across
m ethod
resu lts
of
of
p ath s
a n a ly sis
resu lts
are
1981 . e x p e r i m e n t .
d e scrip tio n
to
E x p lan a tio n s
t
th e
p ro p ag atio n
d ata
The m ajor
5
in
d e tailed
. The
C h ap ters
used
are
-th e
p resen ted
1980
and
in
1981
5 and 6 r e s p e c t i v e l y .
account for
th e
e x p e rim e n ta lly
c h a ra c te ristic s.
resu lts
on
t
fade
d ep th
d istrib u tio n s
are
_
p resen ted
in
th e o re tic a l
p re d ic tio n s
ex p erim en ts?
acrpss
th e
C hapter
The
as w e ll
as
The p e rfo rm a n c e o f
in
p ro p ag atio n
p resen ted
7.
bay <5uring‘ t h e
8
fin d in g 's
C h ap ter
th e
lig h t
ex p erim en ts.and
resu lts
from
p rev io u s
a d ig ita l
rad io
in stalled
1981 e x p e r im e n t
of
th e
F in ally ,
recom m endations
in C h a p te r
r e s u l t s a r e com pared w ith
is
exam ined
r e s u lts o b tain ed
a summ ary o f
for
fu tu re
th e
■b
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
th e
m ajor
research
9.
~\
from
in
is
Chapter 2
MICROWAVE PROPAGATION IN THE TROPOSPHERE
t
^ 2 .1
.
The R e f r a c t i v e
Index in th e T ro p o sp h ere
%
The r e g i o n o f t h e lo w e r a tm o s p h e r e
up.
'
;to
ground
lev el
a p p r o x i m a t e l y 10 km h e i g h t i s g e n e r a l l y r e f e r r e d
as the
tro p o sp h ere.
region
is
w hich
from
P ro p ag atio n
governed
is
a
by
of
m icrow aves in
the r e f r a c t i v e
fu n ctio n
of
the
index n of
atm ospheric
to
th is
the a i r
pressure,
*
tem perature,
a nd h u m i d i t y .
S ince
o n l y a s m a ll amount from u n i t y ,
u s u a lly used is
t h e v a l u e o f ri d i f f e r s by
a m ore c o n v e n i e n t p a r a m e t e r
th e r e f r a c t i v i t y N w hich i s g i v e n - b y
»
N = (h - 1 ) . 1 0 ®
(2.1)
'A lth o u g h N is a d im en sio n less q u a n tity ,
.
.
in
N -u n its
(NU) w h i c h r e p r e s e n t s
A t r a d i o f r e q u e n c i e s up
g i v e n by
to
it
is
o fte n
given
"u n its of r e f r a c tiv ity " .
3 0 , GHz,
the
refractiv ity
[1]
N = 77.6 £ + 3.73 x 1 0 s -
w h e r e P(mb)
is
the
(2.2)
T 2
T ■
ab so lu te
atm ospheric
tem perature,
and e(rab)
♦
pressure,
T(K) . i s
the
*
is the p a r t i a l p re s s u re of
.
w ater v ap o u r.
The
tw o
term s ‘ in
Eq.
(2.2)
are
to
refractiv ity ,
■
*
.
as
u su ally
f
,
referred
th e "d ry " and th e "w et" com ponents o f th e
r e s p e c t i v« e l y .
The c o n t r i b u t i o n
of
7
0
is
,
0
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
the
wet
component i s
increases,
s m a l l a t low t e m p e r a t u r e s .
however,
As t h e t e m p e r a tt u r e
th e v a l u e o f N becomes
very
sen sitiv e
*
i
t o s m a l l c h a n g e s i n t h e h u m i d i t y and t h e t e m p e r a t u r e .
is
due t o t h e
pressure
rapid
v
w ith
in crease
«
in
tem perature.
the
satu ratio n
The e f f e c t i s
T h is
vapour
* • \
illu strated
in
P
F ig.
2 . 1 w h i c h sh ow s t h e v a r i a t i o n o f
t('C )
and
re la tiv e
hum idity
_
correspond
to
the
H(%)
O
p r e s s u r e o f 1000 mb.
.N
w ith
tem perature
an
atm o sp h eric
for
■
T h e c u r v e s f o r H = 0 % and
minimum
a nd ' maximum v a l u e s o f N a t a
given tem p eratu re.
For th e s t a n d a r d a tm o s p h e r ic
of
T' = 288 K, and
P = 1 0 1 3 . 0 mb,
re la tiv e
the atm osphere r e s u l t
w ith
elevation .
pressure,
The
tem perature,
condition
e = 1 1 , 9 mb ( a s s u m i n g a
h u m i d i t y o f 70 %) t h e v a l u e o f N i s
The v a r i a t i o n s o f p r e s s u r e ,
in
H = 100 %
tem perature,
326 NU.
and
hum idity
in a co rresp o n d in g v a r i a t i o n o f N
re la tiv e
!
a nd
N - g r a d i e n t may be i l l u s t r a t e d
co n trib u tio n s
hum idity
of
g rad ien ts
by d i f f e r e n t i a t i n g
the
to
Eg.
the
(2.2)
w i t h r e s p e c t t o h e i g h t h w hich g i v e s
dN _
dh
( 7 7 . 6 | dP
I t
I dh
3.73x10 5
For th e s ta n d a rd a tm o sp h e ric
7 7 . 6P . 7 . 4 6 x 1 0 5 \ dT
--------- +
e -=rm 2
m 3
. _ I dh
(2.3)
de
dh
co n d itio n s
sp ecified
above,
o
Eg.
(2.3)
reduces to
dN
_ 0 _ dP
. , dT , , . de
,HK * ° - 27 d h ■ 1 ’ 3 dK + 4 ' 5 3K
(2.4)
I n a w e l l - m i x e d a tm o s p h e r e V ^ th ^ r e f r a c t i v i t y g r a d i e n t dN/dh
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
9
H =100%
500
3
Z
z
%
400
‘>
a>
DC.
20
300
200
-20
10
0
10
20
^
30
Temperature (,’C)
F ig.
2.1
V ariatio n
of re fra c tiv ity N
w ith te m p e ra tu re t and r e l a t i v e
hum idity H a t a p r e s s u re of
1000 mb.
s
\
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
corresponds
to
essen tially
the
lapse
however, th e \a tm o s p h e re
m easu red m edian o f
kilom etre
above
- 4 0 NU/km.
is
t h e mean v a l u e o f
ground
In g e n e r a l ,
h e ig h t accounts for
the
rate-
a nd
has
an
c o n s t a n t v a l u e o f a p p r o x i m a t e l y - 2 3 NU/km.
V
p ractice,
from
'a d ia b a tic
n o t w e l l - m i x e d and t h e
dN/dh
in
,the
in most te m p e r a te r e g i o n s
the
In
v ariatio n
of
first
is
about
pressure
w ith
r o u g h l y - 3 0 NU/km a n d t h e c o n t r i b u t i o n s
com ponents
due
to
the
normal
h u m i d i t y * and
«
tem perature g ra d ie n ts
+8 NU/km
am o u n t t o a p p r o x i m a t e l y - 1 7 NU/km and
resp ectiv ely
refractiv ity
the f i r s t
N
a nd
[2].
V alu es'
of
the
ground
th e average N - g r a d ie n t o b serv ed over
100 m o f t h e a t m o s p h e r e a t v a r i o u s
N o r th A m erica ^are t a b u l a t e d
lo catio n s
in S e g a l and B a r r i n g to n
in
[3].
%
2.2
P r o p a g a t i o n i n an A t m o s p h e r e w i t h U n i f o r m
't
R e f r a c tiv ity G radient
As a r e s u l t o f t h e v e r t i c a l g r a d i e n # i n t h e r e f r a c t i v e
0
V
J
index,
radio
waves
propagating
through
the
atm osphere
*
g e n e r a l l y do n o t t r a v e l a l o n g s t r a i g h t l i n e p a t h s ,
case of a s p h e ric a lly
m odified to g iv e
stra tifie d
atm osphere, S n e l l 's
in
the
law i s
the r e l a t i o n s h i p
n ( h ) .( h + a ) .c o s ^(h)
- C
(2.5)
*
where n(h)
e a r th 's
is
the r e f r a c t i v e
surface,
a
is
index a t h e ig h t
the e a rth r a d iu s ,
h
(hi
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
above
is
the
th e ray
path angle r e l a t i v e
co n stan t
to th e lo c'al h o r i z o n t a l ,
along a ra y .
th e ray p ath
and
C
is ^ a
The l o c a l r a d i u s o f c u r v a t u r e
P
of
i s g i v e n by t h e e q u a t i o n
i
a
: :
p
It
2_______
( d n / d h ) ' c o s i|>
fo llo w s^ iat,
h o riz o n ta l
g rad ien t,
(2.6)
_______________ , ______
in
for
rays launched a t an g les c lo s e
an ,- a t m o s p h e r e
to
the
w ith a uniform r e f r a c t i v i t y
th e ray p a th w i l l approxim ate a c i r c u l a r arc w ith
*
curvature
—
The
f°r
dh
p
inconveniences
n - 1
associated
„ (2 *7 )
w ith
studying
the
p r o p a g a tio n o f a curved ray p ath over a s p h e r i c a l e a r t h are
v
u su ally
th at
a v o i d e d by t r a n s f o r m i n g t h e c u r v a t u r e s e n t i r e l y
of e ith e r
t h e r a y p a t h o r t h a t o f t h e e a r t h - 1s s u r f a c e
a s shown i n F i g .
ray
path
2.2.
propagates
The f o r m e r c a s e ,
over
a
in which
we
have
a
i
e
In
(2.8)
facto r.
g radient
normal
refractiv ity
c o r r e s p o n d s t o a K v a l u e o f J4 / 3 w h i c h i s
the
o v e r a model
= .K a = ( — — ) a
-Ip - a /
effectiv e
as
latter
w h i c h i s g i v e n by
where t h e q u a n t i t y . K i s c a l l e d t h e
A
curved
the
s t r a i g h t ray p a th s t r a v e l l i n g
e a rth of e f f e c t i v e ,e a rth radius a
t
e
0
a
fla tte n e d -e a f 'th , is u su ally
r e f e r r e d to a s th e F l a t t e n e d - E a r t h m odel.
case,
to
stan d ard
efarth-radius
of
o ften
r d r r a q tiv ity . cond itio n .
radius of cu rv atu re for th is co n d itio n
- 4 0 NU/km
has
considered-
The
a
ray path
valpe
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
four
/
(a) Real earth model:
-actual earth ra d iu s / a
• ray path radius of curvature, P
77TT77777
(b) Flattened-earth model:
• flattened-eorth
•ray path effective radius of curvature, P
e
/ 7 / 7 / / v t v / ~?
r;
/
/ / / / s/ r? /"//?
(c) Straight ray path model:
•straight ray path
•effective ,earth radius, a e
r' ffT T T 7~ T T T T T T T 7
F ig.
2.2
M o d e ls f o r r e p r e s e n t i n g - r a y p a t h
propagating o e a r t h , s u rfa c e .
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
V
^
* ,
tim es
the
earth
r a d i u g ( p * 4 a ) and t h e r a y t h e r e f o r e i s
•
« J
'
r e f r a c t e d away f r o m t h e e a r t h s u r f a c e on a- f l a t t e n e d - e a r t h
*r
rep resen tatio n .
*
I
*
*
*
'
,
* '
•
.
9
#
«
E^or v a l u e s o f d N / d h more n e g a t i v e t h a n - 4 0 NU/km*
the
*
*ri s • r e f r a c t e d . m o r e t o w a r d s t h e e a r t h ' s s u r f a c e and t h e
ray
»
c o n d itio n is described
situ atio n
as
su p errefractiv e.
The
opposite
i n w h i c h d N /d h i s l e s s n e g a t i v e t h a n - 4 0 ;N U /k m i s
d e s c rib e d as s u b r e f r a c t i v e .
• '
The
d iu rn al
and
(
seasonal
r e f r a c t i v i t y g ra d ie n t give r is e
v ariatix n is
to co rresponding
-the ray p a th r a d iu s o f c u r v a t u r e .
T h is in
• •*'
changes
in
the
ang le-o f-arriv al
(AOA),
p la n e , o f the receiv ed ray p a th .
path
ang le-o f-arriv al
[4]-[8],
rep o rted .
and a n g l e
In
were,
ranges
The
stu d ied ,
of
up
to
in
various
0 . 9 qleg
[7],
to
*
•
in th e v e r t i c a l
irr r a y p a t h AOA
s i g n a l l o s s d u e fco a n t e n n a d e c o u p l i n g
lead s
v ariatio n s
by
the.
c h a n g e s in
tu rn
ray
w orkers
have » been
t h e c a s e o f n a r r o w beam a n t e n n a s
l e s s ' t h a n 1 d eg ) , v a r i a t i o n s
in
( b e a h i w id th
may
lead
[8].
to
1
I n g e n e r a l ’, t h e o b s e r v e d r a n g e i n a n g l e - o f - a r r i v a l
dependent
r
on t h e p a t h l e n g t h
’
*■
and W e b s t e r
[9]
suggested the
t
—»
use o f a param eter
"sp ecific
change
in
is
1
a n g le-cff'-arrj-v al
A0 * w h i c h i s d e f i n e d a s t h e c h a n g e i n a n g l e - o f - a r r i v a l p e r
2
'
u n it path le n g th .
The r e l a t i o n s h i p .
*
A6s
where;
= -2 .8 6 x 1 0 "5 .
A| ^ j
g radien t
is
producing
a
given
A0g
,
a(
H )
change
was.
,
/
deg/km
in
the
*
(2.9)
refractiv ity
s u g g e s te d t fo*
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
use
in
e s t i m a t i n g5
the v alu e o f
**
*
-
2.3
A0 &- f o r LOS m i c r o w a v e p a t t f s l\
'
>
'
'
Ray T r a c i n g a n d t h e M o d i f i e d R e f r a c t i v e • I n d e x
\
'
k
i
i
A common t e c h n i q u e o f t e n u s e d
stu d ies
|
in m icrow ave p ro p a g ja tio n
is
th a t of ray tracin g
’
in v o lv es the c a l c u l a t i o n ,
b a s e d on g e o m e t r i c a l o p j t i c s .
,
‘
1
T his
by u s i n g E q . ( 2 . 6 ) ,
of
the
I
ray
p aths
follow ed
by
rays
lau n ch ed
a t v a r i o u s ' ij a u n c h
I
a n g le s fro m 'a t r a n s m ittin g a n te n n a .
The r e s u l t a n t ray p a th .
I
may t h e n
be p l o t t e d
u sin g e i t h e r a f l a t t e n e d - e a r t h or a
s t r a i g h t ray
path
•
t r a n s f o r m a t i o n ’s .
.rep resen tatio n
d ifferen t
is
rep resen tatio n
In
th is
th esis,
the
app ro p riate
/
fla tte n e ^ -e a rth
corresponding
r e f r a c t i v i t y p r o f i l e s may, b e p l o t t e d
allow s fp r lo g ic a l
m uIt ip a th
terrain
to
and co m p ared
p r o f i l e . • T his
approach
r e p r e s e n ta tio n s o f ray p a th s under
propag a t io n ^cond i t i o n s .
In applying the
ray
tracin g
c a b le d 'th e m odified r e f r a c t i v e
in stead of
index is
the
vised b e c a u s e r a y p a t h s
'o n t h e same f l a t t e n e d - e a r t h
also
after
t o Ni by
”
,
a
param eter
index M is c o n v e n ie n tly used
t h e r e f r a c t i v i t y N.
related
'•
tech n iq u e,
T his
m odified
refractiv e
*V
M = N + 1 0 6 . l n ( 1 + ‘j- ]
(2.10a)
,
»
*or
+ 106 ( |
)
for
h «
a
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
(2.10b)
15
♦
*'
*
and t h e g r a d i e n t i n M i s , g i ^ e n bY t*16 r e l a t i o n s h i p
v
cm
an
+ 157
,
NU/km
*( 2 . 1 1 )
•i-
When c o n d i t i o n s
are
such t h a t
a ny r a y l a u n c h e d h o r i z o n t a l l y ,
w ill
trav el p a ra lle l
to
dN/dh
is
A ccording
- 1 5 7 NU/km.
the
e a r th 's
surface,
to £q.
th e v alue of
(2 .1 1 ), the v alue o f *
dM /dh i s z e r o f o r s u c h p r o p a g a t i o n c o n d i t i o n s .
F o r p o s i t i v e ’ v a l u e s o f d M /d h , t h e N - g r a d i e n t
negative
t h a n " - 1 5 7 ‘ NU/km a n d t h e r a y i s
is
refracted
away f r o m
f
,
’ the
fla tten e fl-earth .
dN/dh
C onversely,
m ore n e g a t i v e
refracted
less
tow ards
than
the
dM/dh
is
- 1 5 7 NU/km
dM/dh < 0 i s u s u a l l y u s e d f o r
id en tify in g
neg ativ e
and
fla tten e d -« arth .
\
the
The
I
for
ray
is
* •
condition
the o ccu rren c e o f
,a r a d i o d u c t .
„
The ray t r a c i n g
th at
is
developed
by W e b s t e r
shown i n F i g .
angles
to
the
v ariab le.-
i n t o an i n t e g e r
sub ten d ed
angle
curv atu re
a nd
ray
at
The
tyz
are
The
path,
va^ue
of ^ 2 ,
for
lo c a l ray
path
**
using
Eq. (2 .6 )
path
technique
earth
is
successiv e
radius of
w ith
the
of the lo c a l r e f r a q tiv e
ihdex.
R2 ,
q b t a i n e / 3 by
and
6&
a re then
'/.1
f,
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
then
S tart
the
»
as
each
the e a r t h .
p a t h and
is
geom etry
p ropagation p ath
the c e n tre o f
p ropagation
work
th e ray
nu mber o f i n c r e m e n t s
is I calcu lated
ap p ro p riate
values
69
end o f t h e
on a
th esis
The ra y t r a c i n g
lo cal h o riz o n ta l.
subdivided
p oints
in t h i s
6 sub ten d ed a t th e c e n tr e o f th e
independent
a t one
[10].
2 . 3 i n „which
relativ e
u ses the angle
the
te c h n iq u e used
T h e new
'
■
sim ple
0 . . . cent re of earth
^
P .. . Tocal centre of curvature of ray path
*
*
F ig.
2.3
The Ray T r a c i n g g e o m e t r y .
'
I
)
t
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
17
geom etry.
The
ray p ath c o rresp o n d in g
a n g l e i s c a l c u l a t e d and
p lo tted
procedures.
F u rth erm o re, th e
obtained
summing
by
increm ents
by
t o any g i v e n l a u n c h
repeating
phase
above
p a t h l e n g t h L may be
the i n d iv id u a lphase
6 ^ w ith
the
path
length
*
tSL = n . 6 J I
(2.12)
'
i
where n i s th e r e f r a c t i v e
path
length
i n d e x and
increm ent.
5A
is
the
p h y sical
.
**
-i
In th e ^ c a se o f th e
refractiv ity
m odelling
atm osphere
p ro file,
layers.
common a p p r o a c h o f
allow ing
s m o o th
using
considered a b e tte r
reality .
index s t r u c t u r e s
T his
and
a
non-uniform
an a n a l y t i c e x p r e s s i o n
the r e f r a c t i v e
atm ospheric
having
has
a
the
is
used fo r
associated
advantage,
piecew ise
lin ear
w ith
over the
model,
of
c o n t i n u o u s c h a n g e s i n N w h i c h may be
representation
F urtherm ore,
of
the
situ atio n
in
t h e c h a r a c t e r i s t i c s o f t h e l a y e r may
be v a r i e d by c h a n g i n g
the a s s o c ia te d
param eters
in
the
«
analytic
expression.
The m o d e l l i n g o f l a y e r s
is discussed
i n more d e t a i l i n S e c t i o n 2 . 4 . 3 on t h e d u c t i n g p h e n o m e n o n .
Using th e ra y t r a c i n g
* may
ray
be
in v estig ated
p aths
antennas,
joining
(b)' t h e
angles-of-launch
re la tiv e ' delays.
" is
assumed
th at
technique,
in clude:
the
ray
and
path
param eters
th at
t h e number o f p o s s i b l e
transm itting
a nd
am plitudes,
the
(c)
an g les-o f-arriv al,
In estim a tin g
the
( a)
the
receiving
th e ray path
and
(d)
the ray path am p litu d e s,
refractiv e
index
is
the ,
it
h o riz o n ta lly
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
homogeneous.
The
♦
power d e n s i t y P a t t h e r e c e i v e r
is
c a l c u l a t e d b a s e d on.
-
S ip '
(2.13)
Jh
2.4
then
-f
*
P r o p a g a t i o n i n an A t m o s p h e r e w i t h Non
R e f r a c tiv ity G radient
2 .4 .1
A n o m a lo u s P r o p a g a t i o n
In g e n e r a l ,
th at
the
I
the c o n d itio n s
in t h e a tm o sp h e re a re
a u n i f o r m r e f r a c t i v i t y proflsilre i s
height
ad d itio n ,
range
changes
>
o v e r tim e due
d iu rn al
lead
exam ple,
in
to
heating
to
for
more
propagation.
In
r e f r a c t i v i t y p r o f i l e may o c c u r
f
changes
and
the
effects
of
clim atic
and c o o l i n g c y c l e s .
various
not m a in ta in e d over
tro p o sp h eric
the
'such
anom alous
T h e s e c o n d i t i o n s may
propagation
phenomena.
For
t h a n o n e p r o p a g a t i o n p a t h 'may e x i s t b e t w e e n
the tra n sm ittin g
and
re c e iv in g - antennas
a
condition
which i s ' c a l l e d m u l t i p a t h p r o p a g a t i o n .
T he a d d i t i o n a l p a t h s may b e
o
from
the
ground
atm ospheric la y e r s .
along
or
by
reflectio n
by
a
reflectio n
»
or r e f r a c t i Q n due t o
tra v elle d
they a r r i v e a t th e r e c e iv in g
w ith d i f f e r e n t a m p litu d e s , p h a s e s ,
resu lt
,
S ince th e d i f f e r e n t s ig n a ls
separate p ath s,
co n stru ctiv e
caused
a nd d e s t r u c t i v e
in freq u en cy s e l e c t i v e
a nd
path
antenna
delays.
The
in te rfe re n c e of these s ig n a ls
fading.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
A ccording 'to
th e 'c o n d itio n s under
w hich
they
ex ist,
m u ltip ath
p ropagation
may be c l a s s i f i e d i n t o two d i s t i n c t
%
ty p es.
The, f i r s t
type
occurs
tinder
co n d itio n s
of
a^
relativ e ly
stab le
and
stra tifie d
atm osphere
when
the
V*
m u ltipath
second
i s due to
type
the
occurs
i n f l u e n c e o f l a y e r s of d u c t's.
under
tu rb u len t
co n d itio n s
A s s o c i a t e d w ith re g io n s of a tm o sp h e ric
th is
sectio n ,
it
a ny p a r t .
The
effects
"S.
d is c u s s e d in S e c tio n 2 .5 .
stratified
certain
w ith
inhom ogeneity.
of
ground
atm osphere,
form ation
of
lay ered
reflectio n s
Some
are ad v ectio n ,
su bsidence,
l a y e r s . on r a d i o
propagation,
the
■
d e s c r ib in g th e s e l a y e r s w i l l be
defin ed .
m ore. n e g a tiv e
t h a n -"157 NU/km,
evap o ratio n ,
the
refractiv ity
i.e .
d M /d h ^ 0,
and
id ealized du ct,
a r e shown i n F i ' g .
'
•
*
2.4.
is
Ttfe N-
0
an
for
*
A
the o ccu rren c e of a d u c t.
for
effects
param eters
a necessary co n d itio n for
*
•
hum idity
[11].
of
duct p aram eters,
a
g rad ien ts.
excessive
B efore pro ceed in g w ith the d is c u s s io n o f
M -profiles
y
are c lo s e ly a s so c ia te d
and
g r o u n d h e a t i n g * a nd r a d i a t i o n c o o l i n g
g rad ien t
in
o f t h e atmog^>heric p r o c e s s e s r e s p o n s i b l e
■ fo r such c o n d i t i o n s
0
are
may be f o r m e d
refractiv ity
stru ctu res
in v ersio n s
conditions
stru ctu res
negative
such
tem perature
g rad ien ts.
,
In
’
m eteo ro lo g ical
w i t h i n w hich e x i s t l a r g e
^
is
E f f e c ts ., o f Atm ospheric* L a y e r s
Under
The
and
i s a s s u m e d t h a t g r o u n d r e f l e c t i o n s do n o t
play
2 .4 .2
The
to g e th e r w ith
the
For a h o r i z o n t a l l y
,
•
'
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
-
\
r
2 0
♦
h
AN
M,N
F ig .
*
2 .4
T h e M- a n d N - p r o f i l e s f o r
id e a liz e d e le v a te d d u ct.
an
I
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
21
homogeneous
d u c t , A a nd C mark
t h e d u c t b o u n d a r i e s and h D
is the duct
thickness.
the
^-g rad ien t
is
ducting la y e r
W ithin
negative
[12])
(th is
and h T
is
height
is
the
range
som etim es
layer
AB t h e
c a lle d the
thickness.
The
Xj
duct
strength
i s d e f i n e d as th e t o t a l N-change a s s o c i a t e d
w i t h t h e d u c t and i s g i v e n by AN i n NU.
The
duct
may
be
m o d e l l e d by t h e a n a l y t i c e x p r e s s i o n
x, , » i , AN
. [ 1 2 . 6 3 ( h - h >]
N = NO + kh + —TT. a r c t a n -------t-r------------o
Ah
•-
; . NU
, (2.14)
The c o r r e s p o n d i n g N - g r a d i e n t i s o b t a i no e d by d i f f e r e n t i a t i n g
,Eq.
(2.14)
which g i v e s
dN =' k, i, - -----------------------------------------------7
AN
1 2 . 6 3 Ah
—
d
" (Ah.)2 +’ [ 1 2 . 6 3 ( h - h ) ] 2
m
. ( 2 . 1 5c )^
O
In th e se e q u a tio n s , ,the
b asic
refractiv ity
N - p ro f ile ’ in
thickness
the
ground^ r e f r a c t i v i t y
g rad ien t
k
a b s e n c e " 11*©f
has
fin a l
hQ i s
v a lu e.'
F in ally ,
the change.
The
d escribe
reached
The
the
anomaly
9^percent
of . its
the h e ig h t a t the c e n tre of
'
expressions
-in
*
Eqs.
f o rih s o f t h e s e e x p r e s s i o n s a t e
m odelling,.
is p a rtly arb itrary
t
Snd
th e und erly in g
th e ’ duct.
(2.14)
i d e n t i c a l t o t h o s e u s e d by W e b s t e r
duct
Nq
Ah i s d e f i n e d a s t h e h e i g h t r a n g e b e t w e e n p o i n t s
a t which th e ch an g e in N
for
„„ „
NU/km
and
[10].
and
(2.15)
B asically sim ilar
a l s o e m p l o y e d by Chang
The c h o if c e o f , t h e a n a l y t i c
it
provides , a
«
> are
useful
inv estig atin g
the p ro p a g a tio n e f f e c t s o f d u c ts .
*
♦
**
it
is
im p licit
£n t h e
expression
th at
the
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
[13]
fu n ctio n s
to o l
for
A lthough
N-change
asso ciated
w ith
a
duct is
d e ta ile d N -p ro file data,
v alid
startin g
the
^point
for
sy m m etrical,
in th e ab sen ce of
assum ption
m odelling
is
co n sid ered
such
ducts.*
c o m p l i c a t e d p r o f i l e s may b e s y n t h e s i z e d by s i m p l e
of
the e f f e c t s
v arious
Sheppard
w orkers
[14]
More
addition
o f more t h a n o n e l a y e r .
N u m er o u s s t u d i e s on d u c t s t r u c t u r e s
by
a
[14]-[17]
and I k e g a m i e t
of
have been r e p o r t e d
w hich
al.
[16]
the
are
papers
by
p artic u la rly .
<
d etailed .
Most
p ro p erties,
of
the
howeve"r,
N evertheless,
av ailab le
are
inform ation
from
on
iso lated
duct
events.
a g e n e r a l i d e a may b e g a i n e d o f t h e p o s s i b l e
v alu es of v a rio u s duct p aram eters such
,as
the
h eight
of
AN, and a n o m a l y t h i c k n e s s
Ah.
i
occurrence
Some o f
h Q, d u c t s t r e n g t h
the re p o rte d v a lu e s a re lis-te d in
general
o b serv atio n
fr'om g r o u n d
stren g th
lev el
is
up
The
t h a t d u c t s may o c c u r a t a ny h e i g h t
to r a
fe w
Ah
may
range
from ,
k ilo m etres.
a
The
duct
few
hundreds
of
m etres.
for
B arrin g to n
[3] .
Duct
regions
in
Wh^n t h e d u c t i n g
several
occurrence
N orth
p ro b ab ilities
elev atio n
A m erica
in
are
and
also
Segal
and
ducts,
a nd
*
D u c t s may b e c l a s s i f i e d
d u cts.
t;o
».
average v a lu e s o f 4 d u ct th ic k n e s s /an d
tab u lated
m etres
'
*
„
2.1 .
was r a r e l y o b s e r v e d t o e x c e e d a b o u t - 4 0 NU b u t t h e
value of
elev ated
T ab le
An
layer
in to
elev ated
ground-based
duct is
showri i n F i g .
( r e g i o n AB) o c c u r s a t g r o u n d
the duct is a ground-based d u c t.
$
Reproduced with permission o f the copyright owner. Further reproduction prohibited without permission.
2.4.
lev el,
T able 2.1
Some r e p o r t e d v a l u e s o f d u c t p a r a m e t e r s
in c lu d in g h e ig h t of occurrence h , duct
s t r e n g t h AN, a n d a n o m a l y t h i c k n e s s Ah.
0
Duct p a r a m e te r s r e p o r t e d
^
* r
-
Reference
Sheppard
Lane
$
[14]
[15]
Je-
I
k
h Q (m)
0 - 20"
100
200
1100
1200
400
Ah (m)
AN (NU)
i
-" '
*
j _
-2-0
•*4 0
-30 ' •
* • -25
-40
-10
«■,
50
200
200 '
150
300
100
»
i,
Gossard
k
•
[17]
2750
20
.10
-25
-30
-20
500
40
5
fimwt
1
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
.*
24
One o f t h e mai n c h a r a c t e r i s t i c s o f d u c t e d p r o p a g a t i o n ,
or
ducting,
is
the
trap p in g
of
radio
waves
l a u n c h e d " w i t h i n a c r i t i c a l a n g l e fro m i n s i d e
explain
the
mechanism
for
ducting,
it
t h a t ajre
the d u ct.
To
is re c a lle d
f ro m
S e c t i o n 2 . 3 t h a t i n a r e g i o n w h er e dM/dh i s n e g a t i v e ,
are
bent
tow ards
exam ining F ig .
2.4
the f la tte n e d e a r th
it
is
rays
a nd v i c e v e r s a .
On
se„en t h a t w i t h i n an e l e v a t e d d u c t ,
dM/dh h a s o p p o s i t e s i g n s i n t h e a d j a c e n t r e g i o n s AB and BC.
R ay s t h a t a r e l a u n c h e d a t a n g l e s w i t h i n
±0c
a
c ritic a l
t h e r e f o r e a re b e n t tow ards th e o t h e r
bending w i l l o ccu r
resu lt
is
in
the
reverse
r e g i o n where ra y .
d ire ctio n .^
T his
is
rep resen tativ e
long
illu strated
d istances
in
F ig.
r a y s lau n ch ed both w i t h i n
*
net
2.5
and
w ith
in
low
which
o u tsid e
the
J
d u c t a r e sh ow n.
on r a y t h e o r y ,
It
i s n o t e d t h a t by r e c i p r o c i t y ,
r a y s l a u n c h e d fro m o u t s i d e t h e
be t r a p p e d w i t h i n t h e d u c t ,
h o riz o n ta lly
coupling
homogeneous.
duct
cannqt
a s s u m i n g an i d e a l d u c t w h i c h i s
In
practice,
A f u l l wave
so lu tio n
for
l e a k a g e may b e f o u n d i n Ch
an g [ 1 3 ] .
i
however,
weak
explaining
Over t h e s h o r t
*■
w
u su ally
involved
t h e am o u n t o f d u c t - l e a k a g e
duct
The im p o rta n c e o f d u c t
leak ag e is p r o p o r tio n a l to th e p ath le n g th .
d istan ces
and b a s e d
i n t o th e d u c t can o c c u r th ro u g h a mechanism c a l l e d
duct leakage.
s
The
t h a t t h e r a d i o wave i s g u i d e d o r t r a p p e d w i t h i n
t h e d u c t and c a n p r o p a g a t e o v e r
“l o s s .
value
I
i n LOS c o m m u n i c a t i o n s y s t e m s ,
is
sm all
and
ray
ad eq u ate in th e m a jo r ity o f c a s e s .
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
th eo ry
is
F ig.
2.5
R e p r e s e n t a t i v e r a y s l a u n c h e d from
various p o in ts r e la tiv e to a
propagation" d u c t.
«
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
2 6
An e s t i m a t e
of the c r i t i c a l an g le
g i v e n i n D o u g h e r t y and H a r t
[12]
for- r a y - t r a p p i n g
is
as
r*
t,
♦
0
=9
c
co
= ( 2 . I AM I)"5 ; m r a d ;
1 1 v -
0 (y) = 0
1
C
f o r 0$y$h
CO
L
= eco i + h - h
c (y)
3
U
\
where y ^ s
hL
for
rad io
are the^jlayer th ic k n e s s
(2.16)
*
(2.17)
L
( h T- h _ . ) ^ y ^ 0
JLf U
Li
the d isp lace m e n t of the
and h Q
f o r y- = 0
(2.18)
s o u r c e f r o m B,
a nd
and t h e d u c t , t h i c k n e s s
respectively.
In
must
order
for d u c tin g to o c c u r,
th e,
ducting
lay er
AB
b e m a i n t a i n e d o v e r a h e i g h t o f many w a v e l e n g t h s .
R e q u i r e m e n t was e x a m i n e d
q u alitativ ely
by
using
The
a
mode
t h e o r y o f t r o p o s p h e r i c p r o p a g a t i o n i n B o o k e r and W a l k i n s h a w
[18] .
For ground-based d u c ts ,
ra d io w avelength
anomalyv t h i c k n e s s
max
w h e r e An
value)
an e s tim a te , o f
over
w h i c h c arr b e t r a p p e d by a d u c t o f
Ah(nt)
i s g i v e n by [11] ,
[19]
the
change
in
t h e h e i g h t Ah .
the
(2.19)
refractiv ity
max
is
0 . 5 2 m.
t h e minimum r a d i o f r e q u e n c y a b o v e w h i c h t h e
wave c a n b e t r a p p e d by t h e d u c t i s
d ucts
(absolute
C o n s i d e r a s an e x a m p l e a d u c t
w i t h AN * 20 NU a n d Ah =100 m, t h e v a l u e o f
As
maximum
= 2 . 5 1 x 1 0 * " 3 I - 0 . 1 5 7 ] ^ . A h 3/2
I Ah
I
is
Therefore
the
a p p r o x i m a t e l y 580 MHz.
a r e s u l t o f r a d i o wave t r a p p i n g ,
leads
to
several
radio
the
presence
of
im p o rtan t p ro p a g a tio n anom alies.
*
These are
illu strated
by t h e
effects
asso ciated
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
w ith
a
"ty p ical"
d u c t w i t h p a r a m e t e r s An » - 2 0 NU, Ah = 100. m, and
l o c a t e d a t a h e i g h t o f h Q = 25 0 ', m,.
An u n d e r l y i n g
g rad ien t
o f - 4 0 NU/km was a s s u m e d and t h e g r o u n d r e f r a c t i v i t y
" , absence o f
approach
the duct - i s
30t) NU'.
Us-ing
the
ray
*
and a s s u m i n g , - a h o r i z o n t a l l y u n i f o r m d u c t ,
in th e
tracin g
th e ray
*
paths
for various
rays launched
from
b e l o w t h e d u c t a r e shown i n F i g s .
In F ig .
duct.
As
2 .6 (a),
above,
2.6
(a)
to
w ith in ,
( c) ,
the r a d io s o u rc e i s lo c a te d above
m entioned above,
trap p in g
a nd
the
does not occur e x c e p t
-m
f o r weak c o u p l i n g
in to
a rad io-hole e f fe c t
th e d u c t through le a k a g e .
is observed
in r e g i o n A w hich i s c a u s e d
by a d e f o c u p s i n g m e c h a n i s m d u e t o
fla t
fading
may
occur
as
However,
a
th e/^d u ct.
resu lt
S u b stan tial
of the d efo cu ssin g
m echanism .
are
Rays la u n c h e d from a s o u r c e l o c a t e d
w ith in ' the
duct
1 *
shown
in F ig . 2 .6 ( b ) .
A gain th e r a d i o - h o l e e f f e c t i s
observed
in r e g i o n
pro pagation
path .
is
D ucting
A
a
in
essen tially
is
observed
i
p ro p ag atio n occurs
For
w hile
radio
regions
norm al
and
lab elled
B the
>
. w i th one r e c e i v e d ra y
as
a
resu lt,
m ultip ath
i n r e g i o n s l a b e l l e d C.
source lo c a te d
below
the du ct,
the
ray
■
0
*
paths
are
shown
.in
F ig.
2 .6 (c ).
p o s s i b l e e x c e p t f o r weak c o u p l i n g
absence o f ground r e f l e c t i o n s ,
su p p o rted .
case
is
A gain t r a p p in g
in to
the
d uct.
a
resu lt
of
in su ffic ie n t
long d i s t a n c e s 'c o n s i d e r e d
In
m u ltip ath pro p ag atio n
»
The r a d i o - h o l e e f f e c t o b s e r v e d a t
A
is not
the
is not
in
antenna h e ig h t fo r
a nd n o t d u e t o
the
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
presence
th is
the
of
-£300
-3 0 0
M, 10NU/div.
Fig.
20
40
60
D istance from tra n sm itte r
2.6 ' P ro p a g a tio n in th e
( a) r a y s l a u n c h e d
* (b) r a y s l a u n c h e d
(c) r a y s l a u n c h e d
80
( km)
presence of a duct.
from, a b o v e t h e d u c t .
from w i t h i n t h e d u c t,
from below t h e d u c t .
/
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
the d u ct.
,
«
2 ;4 .3
M ultipath P ropagation
A
type
atm osphere
of
is
m ultipath*
tu rb u len t
in a T u r b u l e n t Atm osphere
fading
but
may
occur
not w ell-m ixed.
when
the
R egions of
i n h o m o g e n e i t y i n t h e r e f r a c t i v i t y g r a d i e n t may c a u s e
and
random f l u c t u a t i o n s
rapid
i n b o t h t h e a m p l i t u d e and r e c e i v e d
phase of the r e s u l t a n t s i g n a l .
To u n d e r s t a n d t h e m e c h a n i s m f o r
for
the
moment
refractiv ity
of
th at
a
sm all
t h e main r a y p a t h .
sm all re g io n .
is
above
g r a d i e n t everyw here
r e c e i v i n g ’ ante-nna.
resu lt
o f u n u s u a l l y highthe
However,
ad d itio n al
for
region,
th is
in the
n o r m a l l y do n o t t e r m i n a t e
r a y b e n cting o c c u r s
ttflat
jnid-point
’ except'
The r a y s p a s s i n g t h r o u g h t h i s
extra
co n sid er
The a tm o s p h e r e i s assunied t o have a
absence of th e inhom ogeneity,
gradient,
region
g ra d ie n t occurs s lig h tly
uniform r e f r a c t i v i t y
t^
such f a d in g ,
rays
due
to
in t h i s
the
at
abnormal
region
a nd
the
may r e a c h t h e r e c e i v i n g
a n t e n n a , w i t h a m p l i t u d e s and p h a s e s d i f f e r e n t f r o m t h o s e o f
the
nom inal
ray!
region d is tr ib u te d
resu ltan t
Now
if
t h e r e e x i s t m ore t h a n o n e s u c h
random ly along
s i g n a l would be t h e v e c t o r
>
of sig n als
re la tiv e
the p ro p a g a tio n p a th ,
each w ith random ly v a r y in g
*
delay tim e.
sum o f a l a r g e
*
the
number
am plitude,, p h a s e ,
and
»
. Dufe t o t h e ra n d o m n a t u r e o f t h e m e c h a n i s m i n v o l v e d ,
sta tistic a l
approach
i s more s u i t a b l e
for d escrib in g
a
th is
#
type of fa d in g .
When c o n d i t i o n s
are such t h a t :
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
(a )
there
^
ex ist
a large
num be r o f i n t e r f e r i n g
of each i n t e r f e r i n g v e c to r
(c)
the
am plitude
is
vecto rs,
uniform ly
of the v e c to rs
are
(b)
th e phase
d istrib u ted ,
'a n d
norm ally d i s t r i b u t e d
i
about zero am plitude,
of
the
[20]
. . .
vecto rs
[21] .
is/d escfib e d
The
d istrib u tio n
t h e n •the am p litu d e o f
jt
the
resu ltan t
by t h e R a y l e i g h d i s t r i b u t i o n
fu n ctio n al
form
of
the
R ayleigh
is
P (A*JL) = 1 - e x p ( - L z/ a )
where P (A < L )
the
is
resu ltan t
(2.20)
the p r o b a b i l i t y
sig n al
th at
the
i s below a g iv e n
am plitude
l e v e l L,
a nd
A
of
a
is
t h e mean s q u a r e v a l u e o f A.
In g e n e r a l ,
type
fading
is
d istrib u tio n
w hich
the
not
shape of
param eter
esp ecially
its
sa tisfie d .
A
by
a
R ayleigh
m ore g e n e r a l
Nakagami
[22]
in
m.
The
and.
fu n ctio n
it
describ es
includes
the
the
R ayleigh
as a s p e c i a l c a s e .
is o fte n
although
for
t h e f u n c t i o n may b e v a r i e d by c h a n g i n g
R apid b u t m ild f a d i n g
p aths
required
proposed
m -d istrib u tio n
d istrib u tio n
r
alw ays
f u n c t i o n was
an e m p i r i c a l
Nakagami
the. c o n d itio n s
attrib u ted
effects
observed
most
p ro pagation
t o a R a y l e i g h t y p e mechanism
are
tra n s-h o rizo n ,
on
m or e.
pronounced
paths.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
on
[20]
long,
31
2.5
T errain E ffe c ts on Radio Wave Propagation
2 .5 .1
P a t h C l e a r a n c e and t h e F r e s n e l Zone
Adequate
u n derlying
If
clearance
terrain
jr
of
the
ray
path
above
the
i s r e q u i r e d on a LOS p r o p a g a t i o n p a t h .
s u f f ic ie n t clearan ce
is not allow ed f o r ,
sig n al
fading
J .
due
to
terrain
mechanism.
blockage w i l l occur
through a d i f f r a c t i o n
P a t h c l e a r a n c e may be q u a n t i f i e d
by
using
the
c o n c e p t of F r e s n e l Zones.
C onsider
A ccording
a
point
along
a LOS
t o H uygen's p r i n c i p l e ,
propagation
the f i e l d
path.
re c e iv e d a t the
receiving
a n t e n n a i s a sum o f t h q f i e l d s - e m i t t e d by a l l
H uygen's
s o u r c e s d i s t r i b u t e d on a s u r f a c e p e r p e n d i c u l a r
the
away
path.
The r a d i a t i o n
f ro m t h e
and t h e r e f o r e
♦ which
the
are delayed
phase,
distances
is
in p h a s e .
are
ex actly
in te g ra l m u ltip les of
„
k
( 2 . 21)
.
the' r a d i u s of th e n - th
w a v e l e n g t h , - .an d
of
fu rth er
The l o c i of p o i n t s - f o r
are g iv e n by
_ di+d2
w h e r e F^ (m)
rad iatio n
lags
n \d id 2
=
n
to
LOS p a t h t r a v e l l e d t h r o u q h g r e a t e r d i s t a n c e s
half-w avelength
F
f ro m t h e s o u r c e s t h a t a r e
the
the
p o in t
on
di(n>)
the
locus,
a nd
ray
x(n>) -is
d 2 (m)
path
the
are
from
the
t r a n s m i t t i n g .and r e c e i v i n g a n t e n n a s .
The r e g i o n e n c l o s e d by F ,
and f
is called
the
*
n-1
n
n rth . Fresnel
Zone $nd r a d i a t i o n f r o m s o u r c e s l o c a t e d on
s u c c e s s iv e F r e s n e l zones are
in p h a s e o p p o s i t i o n .
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
M o st
of
^
32
the
power r e c e i v e d a t t h e r e c e i v i n g
by t h e f i r s t few F r e s n e l Z o n e s .
propagation
clearance
Fresnel
path
is
k = h /F 1
Zone.
often
where
In t h i s
antenna is c o n tr ib u te d
The c l e a r a n c e
expressed
F^ i s
as
h(m)
a
of
norm alized
th e ra d iu s of the
th e s is path c le a ra n c e s
kF, .
1
D iffra c tio n lo ss curves for d if f r a c tio n
a
.first
are w r i tt e n
in t h e form
<^r
o b s t a c l e a r e shown i n F i f j .
d iffractio n
2.7.
by
a
sin g le
For a . g i v e n p a th c l e a r a n c e ,
l o s s d ue t o a k n i f e - e d g e o b s t a c l e h a s a minimum
value.
The p a t h c l e a r a n c e on a LOS p a t h d e p e n d s on t h e am ount
of
r a y b e n d i n g w h ic h i n t u r n i s a f f e c t e c T \ ^ y / ^ h e N - g r a d i e n t
in the atm osphere.
\|£afle
S i n c e t h e l a t t e r q u a n t i t y c a n assu m e
a ?
. . .
ra n g e 'N o f v a l u e s , p ro p e r p a th d e s ig n m u st^ en su re t h a t
adequate c le a ra n c e is m ain tain ed for
all
the
an ticip ated
s
v a l u e s o f d N / d h o c c u r r i n g on t h e p a t h .
2 .5 .2
R e f l e c t i o n , f ro m t e r r a i n
stru ctu res
I n LOS m ic r o w a v e p r o p a g a t i o n ;
acts
as
a surface th a t s c a tte rs
back i n t o th e atm o sp h e re .
scatterin g
nam ely,
the
the
u nderlying
terrain
in c id e n t rad io energy
The r e s u l t a n t f i e l d d u e t o
th is
may be c o n s i d e r e d a s t h e sum o f two c o m p o n e n t s ,
t h e s p e c u l a r c o m p o n e n t and t h e d i f f u s e c o m p o n e n t .
The s p e c u l a r c o m p o n e n t i s
4
a r e s u lt of r e f le c tio n
t h e s u r f a c e and h a s c o h e r e n t p h a s e .
energy o r ig in a te s
co ntained
w ithin
fro m t h e p a r t o f
the
first
M o st o £ t h i s
the
Fresnel
surface
E llip se.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
from
reflected
which
is
Fo » m o s t
30VdS 33 * 3 W0U3 flp
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission
34
s y m m e t r i c a l LOS p a t h s ,
p o in t
to
the
much , g r e a t e r
F resnel
E llip se,
co n d itio n
first
e sp e c ia lly
E llip se
~ •
1)
sm
IX
and
th an
ap p lies,
F resnel
A ppendix
d istan ce s
tra n sm ittin g
u su ally
th is
th e
th e
for
th e
th 6
th e
receiv in g
sem i-ax es
a t m icrow ave
sem i-ax es F
■
>*
a curved
reflectio n
an tenn as
of
th e
first
frequencies-.
IX
earth
and
F
are
XY
g iv en
are
W h en
of
th e
by
(see
j
ARiR2*
( R i + Ri )
y
from
h
(2 . 2 2 )
and
\ F
w here
A is
from
is
the
th e
th e w av elen g th ,
reflectio n
reflecftio ri
an g le),
D
is
cu rv atu re,
(2 .2 3 )
A R' x R 2
(Ri + R 2 )
1Y
an g le
th e
and
p o in t
th e
Rj
and
to
th e
R2
(som etim es
d iv erg en ce
su b sc rip ts
are
et h e
tw o e n d s o f
th e p a th ,
also
th e
c alled
co efficie n t
X
d istan ce s
and
Y
due
d enote
y
g razin g
to
earth
th e
axes
«*■
p arallel
and p e r p e n d i c u l a r
U n lik e
d iffu se
th e
area
p ath ,
u n less
phase
of
in
th is
th ecp ath .
s p e c u la r com ponent,
sc a tte rin g
en tire
to
. cogrponent
betw een
th e
h ig h ly
th e
energy
of
o r i g i n a t e s from o v e r
two
ends
d ire c tiv e
o i . th e
an ten n as
c o m p o n e n t -As i n c o h e r e n t
and
- *
are
its
am p litu d e
In
u su a lly
g en eral,
sca tte rin g
be d o m in an t,
ex ist
[24] .
are
T herefore,
observed
b o th
for
sp ecu lar
sim u lta n e o u sly
d epending
on
th e
fast
fc
usedj
is
4
flu c tu a tio n s
reflectio n
th et e r r a i n
The
am p litu d e
d ifF u se
alth o u g h
th e
p ro p ag atio n
m
R ayleigh d i s t r i b u t e d
th e
in
com ponent.
and
d iffu se
o n e o f w h i c h may
p ro file
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
and
th e
35
M
* surface^
roughness
c h a r a c t e r i s t i c s . , The e f f e c t s
* o f t h e tw o c o m p o n e n t s
may
be
q u an tified
by
d efin in g
*
th e R e f le c tio n C o e f f i c i e n t R such t h a t
*
param eter c a lle d
=
r
the*
and E ^ a - r e
scatte red
,
E i
a
'
(2.24)
•
fi.eld s t r e n g t h s o f the
the
fie ld s,
♦
’
,
,
w her^E j
of eith e r
i n c i d e n t and =
and t h e r e ' f l e c t i o n c o e f f i c i e n t t a k e s
*
i
on v a l u e s R = R
and
R = R . for
s
d *
d iffu se
com ponents
resp ectiv ely .
the
s p e c u l a r ■ a nd
These d re ^ d isc u s se d
»
m ore d e t a i l
In
The
the
disqussion
of
m ultipath
reflectio n s
were
*■
th a t atm ospheric e f f e c t s
may b e
effect
u nd erlyin g
in ;
*
in C h a p te r 5.
S ectio n 2 .4 ,
order
the
ground
of
ground
terrain ,
is
pro p ag atio n
not
in
co n sid ered
w ell
in
illu strated .
r e f l e c t i o n s , when s u p p o r t e d by t h e
to
reflect
*
a t m o s p h e r e and t h u s c a u s e
energy
back
in to
the
5:1
ex tra
ra y pa£hs to be r e c e i v e d .
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
C hapter 3
THE EXPERIMENTAL EQUIPMENT
3.1
In tro d u ctio n
T he e q u i p m e n t
co n sists
.
-of
a
used
M icrowave
.
s w eep
the
propagation
D iagn ostic
System
a nd
f r e q u e n c y a m p l i t u d e a nd p h a s e r e c o r d s ,
frequency
records,
D iagnostic
m agnetic
d escribed
tape
in
form
w e r e made
System .
The
to g e th e r w ith tim e in fo r m a tio n ,
w e r ^ g a t h e r e d by t h e D a t a A c q u i s i t i o n S y s t e m
on
a D ata
f
i,n t h e
P ro p a g a tio n m easurem ents,
t h r o u g h t h e u s e o f t h e Microwavt^
sweep
experim ents*
.
A c q u i s i t i o n System .
of
in
d ig ital,
form .
a nd
These
recorded^
system s a re
i n S e c t i o n s 3 . 2 and 3 . 3 r e s p e c t i v e l y .
I n t h e 1981
experim ent,
a
d ig ital
radio
test
was
c a r r i e d o u t s im u lta n e o u s ly w ith th e p ro p a g a tio n ex p e rim e n t.
The
configuration
of
c
the
te le p h o n e com panies i s
3.2
3 .2 .1
d ig ital
described
radio
used
by
the
in
the
in S e c t i o n 3 . 4 .
The Microwave D iagnostic System
^Jh era l
The
D escription
m icrowave
diag n o stic
prop agation
experim ents
was
*
m easurem ents o f th e
received
ray
system
used
desig n ed
p ath
param eters
%
.
>
■
3
to
6
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
provide
on
a
37
propagation
p ath.
.the p a ra m e te rs are
In
the case of a s in g le
the a m p litu d e
and
received ray,
an g le-o f-arriv al
of
j
th e
received
ray
path.
propagation,
the p a ra m e te rs
ray
th£
p ath s,
in d iv id u al
rays,
In
the
include
am plitude
and
case
of
m ultipath
t h e number o f
received
an g le-o f-arriv al
a nd t h e r e l a t i v e
tim e
d elay
of
the
betw een
the
in d iv id u al rays.
The b a s i s o f th e m icrow ave d i a g n o s t i c
system
sweep f r e q u e n c y p h a s e - s w e p t i n t e r f e r o m e t e r .
d e v e l o p e d and a p r o t o t y p e was b u i l t
S cience,
the
U n iv ersity
of
accuracies
of
resp ectiv ely .
W estern
b etter
tim e
than
The f o l l o w i n g
sectio n s
and W e b s t e r a nd Ueno
. The
am plitude range
and
summ arize
system .
et
of
ray p ath
v ariatio n s
+ 0 .1 deg
d e s c r i p t i o n s may b e f o u n d i n W e b s t e r
3 .2 .2
O ntario.
d elay
f e a t u r e s o f .the i n i c r o w a v e d i a g n o s t i c
[26],
T h e s y s t e m was
a nd i s c a p a b l e o f p r o v i d i n g m e a s u r e m e n t s o f
a n g l e - o f - a r r i v a l and r e l a t i v e
the
a t th e C e n tr e f o r Radio
e x p e r i m e n t a l e q u i p m e n t h a s an o p e r a t i n g
40 dB
is
+ 0.05
the
w ith
nsec
m ajor
More d e t a i l e d
a l..
[25] ,
Ueno
path,
the
[7].
P r in c ip le of O peration
C onsider
ap p licatio n
the
of
case
the
of
one
d istin ct
phase-sw ept
m easurem ent o f th e a n g l e - o f - a r r i v a l
ray
in terfero m eter
j.s shown
in
in
F ig.
t h e "■
3.1. *
*
The
incom ing
sig n al
spaced a d is ta n c e D
is
r e c e i v e d on t w o a n t e n n a s w h i c h a r e
apart
in
the
plane*
containing
the
r
req u ired
an g le-o f-arriv al.
Thds r e s u l t s
i n tw o s i g n a l s o f
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
♦
to
© * —0
ir
- - - - - Q
f0 - fr
---------------K E ) -
'r
- ©
Phase
Meter
V
I,r
V
+
A
*- + «*
V
V
9
0
IAI
1
F ig.
3.1
The p h a s e - s w e p t i n t e r f e r o m e t e r
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
[7]
t h e same f r e q u e n c y b u t w i t h
a phase d i f f e r e n c e
<J> g i v e n by
t
, _ 2TTfD s i n 9
c
forr 0
thjb
s m a l l , where
of
frequencies f
o sc illa to r
sig n als,
and
(3.1)
j
radio frequency
the
the
are h etero d y n ed w ith
of a reference
be
f is
an g le-o f-arriv al
sig n als
of
_ 2frfD9
”„ c
(f
in cid en t
two l o c a l
-
ray.
f r ) , where f r i s
a t frequencies
co n sid ered
as
and
f
r
<< f
( f - f ) and
having
o
.
for
the
a d d itio n of these
filte rin g
phase
e
, m easured
reference
e
a
the '
f Q) b u t
( 2 -rrf^t + 41) ,
thus
m eter,
The
and
w hich h as a
re la tiv e
t o •'th e
[26]
i
in cluding
system .
an g le-o f-arriv al
An
an a r b i t r a r y p h a s e
unam biguous
sh ift
m easure . o f
i s o b t a i n e d by s w e e p i n g t h e
radio
the
sig n al
thus
=
df
sen sitiv e
(f -
w ith su b se q u e n t d e t e c t i o n
phase
IF
(3.2)
through
p ro v id ed
lo cal
o
is a co n sta n t
f,
above
+ <t>
c
w h e r e <j>
frequency
the frequency
in a s ig n a l o f freq u en cy f
by
two
sig n als
term " p h a s e - s w e p t i n t e r f e r o m e t e r " .
s i g n a l g i v e n by
= —
These
The r e s u l t i n g
t h e same f r e q u e n c y
IF s i g n a l s
resu lts
the
9 is
( f - f Q + f r ) may a l s o
w ith ' a tim e v a ry in g p hase d i f f e r e n c e o f
accounting
and
o scillato r
s ig n a l used for g e n e ra tin g
frequencies
(RF)
2TTD6
.
,
■*
(3.3)
c
th a t.c a re
to
is
taken
v ariatio n s
to
in
ensure
frequency.
th at
4
is
not
ro
The s l o p e o f th e
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
40
X
measured phase
t*
v e rsu s frequency f th u s
e
gives
• .
a
-
d irect
m easure of th e ray p a th a n g l e - o f - a r r i v a l .
The sw eeping o f th e r a d i o f r e q u e n c y
id en tify in g
the
of m ultipath
co n sid erin g
vector
r e la tiv e path
propagation.
relativ e
(or tim e)
T h i s ' may
t h e two p a t h s i t u a t i o n
a d d i t i o n o f two s i g n a l s
tim e
delay of
Ax
is
also u sefu l for
delay in the case
be
illu strated
shown i n F i g .
o f a m p l i t u d e s 1 and
resu lts
3.2.
r
by
The
w ith
i n a s i g n a l A(u)) g i v e n
by
A ((aj) = 1 +
where
w = 2 ^ f,
=
and
|A(a)) | e ^ (a))
|A(u) | and
4>(u>) a r e
(3 *4 )
the am p litu d e
and
r e l a t i v e p h a s e o f t h e c o m p o s i t e s i g n a l g i v e n by
| A ( <jo) | = [1 + r 2 + 2 r . c o s (a). Ax) ] 2
(3.5)
and
<J>(w)
= tan~ 1
The a m p l i t u d e o f
th erefo re
is
tl
the
p erio d ic
*s _ii (fei- Ax.),
com posite
sig n al
v e rsu s frequency
a s shown i n F i g .
3 . 3 and t h e p e r i o d
Af i s r e l a t e d t o t h e r e l a t i v e
or
(3 . 6 )
1
+ r . c o s (to - A x ) J
t i m e d e l a y by
Aui.Ax = 2 tt
"X.
* oN—
At - i f
(3.7)
(3.8)
The r e l a t i v e
a m p l i t u d e and r e l a t i v e
paths
thus
may
Ije
derived
tim e d e la y o f
from*
the
sw eep
a m p l i t u d e r e c o r d by a F o u r i e r T r a n s f o r m ' t e c h n i q u e .
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
the
ray1
frequency
41
A(w)
Fig.
3.2
V e c t o r a d d i t i o n o f tw o s i g n a l s w i t h a
r e l a t i v e t i m e d e l a y o f At.
*
1
"
o. (1- r) —
Frequency
F ig.
3.3
A m plitude c h a r a c t e r i s t i c s o f t h e .
r e s u l t a n t o f tw o s i g n a l s w i t h r e l a t i v e
t i m e d e l a y o f At .
' A.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
42
To o b t a i n t h e a n g l e - o f - a r r i v a l o f t h e
(
p aths
i n a two p a t h s i t u a t i o n ,
m eter o u tp u t
e
is
*
X
now
individual
ray
o ne o b s e r v e s t h a t t h e p h a s e
the
relativ e
phase
d ifferen ce
»
b e t w e e n t h e c o m p o s i t e s i g n a l s on t h e t w o r r e c e i v e r c h a n n e l s .
The, a n a l y s i s , i n t h i s c a s e i s n o t a s s t r a i g h t f o r w a r d b e c a u s e
the
m easured
phase
e
is a f u n c tio n of b o th the r e l a t i v e
d e l a y and t h e a n g l e - o f - a r r i v a l o f t h e i n d i v i d u a l r a y s .
An
/
example
o f t h e sweep f r e q u e n c y a m p l i t u d e 7 and p h a s e r e c o r d s
s i m u l a t e d f o r a two p a t h s i t u a t i o n
Co m p u ter
sim ulations
revealed
is
'shown
th at,
a n g l e - o f - a r r i v a l o f the s tr o n g e r path
general
slope
of
the
a n g le -o f-a rriv a l ' of
phase
the
in
for such c a s e s ,
is s t i l l
record.
second
To
estim ate
path,
in v o lv es
the
syn th esis
however,
sy n th esizin g
ttfe
phase p a t t e r n .
of
the
A lthough
very
rath er
#
may
be
obtained
time consum ing.
The
abo ve
in
T his
by
an g le-o f-arriv al
s
values
a
o b s e r v e d sw ee p f r e q u e n c y
accurate
s
the
.
ang les-o f-arrival
experim entally
the
9
t e c h n i q u e has t o be u s e d .
estim atio n
3.4.
g i v e n by t h e
f
trial-an d -erro r
F ig.
%
th is
-
manner,
the p ro c e s s i s
.
an aly sis
may
sim ilarly
be
extended
s i t u a t i o n s w i t h m6 r e tt^an two r e c e i v e d r a y p a t h s .
a n a ly s is procedure is s im i l a r to
th at
for
the
to
The d a t a
two
path
situ atio n ,
w ith
t h e r e l a t i v e a m p l i t u d e s and . r e l a t i v e t i m e
»
_i
d e l a y s e s t i m a t e d by a F o u r i e r T r a n s f o r m t e c h n i q u e
and
the
\
an g les-o f-arriv al
d e r i v e d ,fr om p a t t e r n s y n t h e s i s .
c a s e s th e p a t t e r n ' w i l l be
.
*
’
co n sid erab ly
*
-
In such
m o re ' complex
r
c o n s e q u e n t l y w i l l r e q u i r e more t i m e f o r
its
an aly sis.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
and
43
•»
■o
-10
Ql
< -20
%
a
10.0
9.5
Frequency
Ampl. (dB)
*
Fig.
*
A 0 A (deg)
10.5
(GHz)
Delay (ns)
0.0
-0 .20
-
-10.0
-0.40
4.0
3.4
S y n t h e s i z e d sweep f r e q u e n c y a m p litu d e
a n d p h a s e r e c o r d f o r tw o r e c e i v e d r a y
paths.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
3.2.*3-
Equipm ent D e t a i l s
v
?
T h e •e x p e r i m e n t a l d i a g n o s t i c
system
*
was
designed
to
t
'w
,*
'■
operate
at
X-band
(8.5
to
1 2 . 0 GHz)
frequencies.
To
<3
m easure r e l a t i v e
t i m e d e l a y s i n t h e 1 t o 10 n s e c r a n g e
ray p ath a n g le s - o f r a r r d v a l
i n t h e r a n g e +1 d e g ,
s w e e p o f 1 GHz i s r e q u i r e d
and t h e r e c e i v i n g
and
a frequency
antennas
are
*
spaced 3 m a p a r t.
The b lo c k d ia g r a m o f th e d i a g n o s t i c
is
shown
in
sig n al th a t is
F ig.
swept in
e v e r y 10 s e c d n d s ^
is
3 >5 .
The
tran sm itter
frequency
at
t r a n s m i t s al CW
through
a
1 GHz
ban d
T h e s w e e p h a s a d u r a t i o n o f 1 . 2 8 s e c and,
a c c o m p l i s h e d v i a 64 d i s c r e t e
spaced
system t r a n s m i t t e r
16 MHz i n t e r v a l s .
(Y ttrium -Iron-G arnet)
frequency
step s
which
The m i c r o w a v e s o u r c e
- Tune d Gunn d i o d e
are
i s a YIQ
O scillato r
(YTO)
the 'o u tp u t
f r e q u e n c y o f w h i c h i s c o n t r o l l e d by a u x i l i a r y
"/
<■
sw eep c o n t r o l c i r c u i t r y .
T h e l a t t e r a l s o g e n e r a t e s a sw ee p
-
s t a r t m a r k e r s i g n a l w h i c h is, u s e d t o f r e q u g j i c y m o d u l a t e t h e
«*■
YTO
to
mark
the
synchronization."
sta rt
of
To o b t a i n
each
sweep
for
receiver
tfte r e q u i r e d p o w e r l e v e l s ,
the
o u t p u t f r o m t h e YTO i s a m p l i f i e d by a t r a v e l l i n g - w a v e
tube
if*
(TW£) a m p l i f i e r .
The a m p l i f i e d s i g n a l i s t r a n s m i t t e d on a
p a r a b o l i c d i s h a n t e n n a and t h e t r a n s m i t t e d s i g n a l l e v e l
'
is
v
m aintained
c o n s t a n t t h r o u g h o u t t h e s w e e p by a u t o m a t i c g a i n
t
con tro l
The
C o n sists
(AGC)
us 4ng a # I N - d i o d e m o d u l a t o r .
d iag n o stic
of
system
receiver,
two e s s e n t i a l l y p a r a l j ^ l
an i n t e r f e r o m e t e r a r r a n g e m e n t .
shown
in
F i g . ,3.6
r e c e iv e r channel^
The f i r s t
lo cal
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
in
o scillato r
R eproduced
with perm ission
of the copyright ow ner.
TOP WALL
DETECTOR
AGC
Further reproduction
YTO
S w eep
Control
PIN
Diode
Modulator
TWT
prohibited without p e rm issio n .
TX
' Antenna
FM Sweep
Marker
Generator
10 MHz Ref. Osc.
\
Fig.
3.5
s’
Block diagram of^fckeDiagnostic Sy.s-tem transmitter
Ut
R eproduced
with perm ission
of the copyright ow ner.
150 MHz
10.70MHz
64M H z/
■w
Further reproduction
C
e
YTO
IAI
5130
M H z(~ ]
M aster Osc.
10 MHz
i
RX ■
A ntenna
=9
M agcM
IV CO
- 0 8 6 MHz
( p \ ----- / Z ) _ l
>N'lnki
lOKHz 0
'D ig ita l
Phase
M eter
-O H
5129
MHz
64 MHz
10.71MHz
— -**- -HagcI—
150MHz
|
prohibited without p e rm is sio n .
54 0 M^
Sweep
Control
Phase
Lock &
Lfl«S_
64 MHz
r
Real Time
Clock
t ime
data
**MP— sw eep s t a r t m ark er p u lse
Fig.
3.6
sync.
clock
Block diagram of the' Diagnostic System Receiver,
4 6
47
is
.
a
YTO
the
sy n ch ro n ized to the
output
sweep*, f r e q u e n c y
received s ig n a l
(through
o f w hich
the
.is
FM" s w e e p
•
i
sta rt
m arker)
frequency
the
RF
(IF)
but
offset
at all
by
tim es.
T his
s i g n a l on each 1 c h a n n e l,
the f i r s t
IF
of
m ixers.
" A fter
1 .
em ployed
to
the
first
.in term ed iate
i s u s e d to.dow n ' c o n v e r t
a t each frequency
150 MHz’ . t h r o u g h
the
use
of
step ,
to
w aveguide
am p lificatio n ,
a phase l o c k i n g ' te c h n iq u e is
' '
:
c o n v e r t t h e s i g n a l s t o *the a c c u r a t e s e c o n d
1
IF
o f 64 MHzS
S i n c e t h e same l o c a l o s c i l l a t o r
*
id e n tic a l c irc u itry
both c h a n n e ls ,
ace used fo r
th e phase
» i
3
'
the
down
info rm atio n
s i g n a l s ' , and
conversions
in
i n t h e two s i g n a l s
1S
i
J
t
%
preserved.
r
A fter
araplificsation,
*
converted,
once
more
• «
t h e Second IF
*»
r
sig n als
*
td the
th ird
^
down
are
IF u s i n g two i n d i v i d u a l
\
lo cal o s c illa to r
frequency
sig n als
separation of
at
reference
m eter.
The
anch ,*53'.29 MHz.
The
t h e s e tw o l o c a l o s c i l l a t o r - s i g n a l s
are m aintained a c c u ra te ly a t
the
53.30
10 KHz by p h a s e
locking
w ith
10 KHz s i g n a l -tha"t i s ‘s u p p l i e d t o t h e p h a s e
resu ltin g
t h i r d “ IF
sig n a ls,
at
10.70
and
. 7 1 MHz - r e s p e c t i v e l y ,
by a u t o m a t i c
gain-
*
are m aintained a t c o n s ta n t le v e ls
V.
*
n
*
co n & o l.
For phase
m easurem ents
as.
*
‘
d escribed
in
the
previous s e c tio n ,
s i g n a l s f r o m t h e two
\
‘
’ *
C h a n n e l s a r e a d d e d , d e t e c t e d , an d f i l t e r e d
to
produce
a
10 KHz
r
A
s i g n a l s - " The
•
*
r e f e r e n c e 10
*
phase
KHz s i g n a l
m etef.
channels
is
»
phase<of
th is
0
sig n al re la tiv e
.
is
m easured^
by
a
8- b i t
The s i g n a l a m p l i t u d e on o n e o f t h e
a l s o m easured &
m onitoriifb
■
d ig ital
receiv er^
t h e AGC l e v e l s
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
r
to the
and'
48
is
made
av ailab le
in
8- b i t
d ig ita l
form
th ro u g h
th e
use
\ “an
a n a lo g -to * d ig ita l C o n v erter
A
sweep
clo ck
a sw eep.
hardw are
*
The
w ere
F in ally ,
. ,
’
tra n sm it
ex p erim en ts
an ten n as
for
clo ck .
w ere
is
av ailab le
*
s y n c h r o n i z i n g ct h e
d ata
th e
p ro v id e d
real
'■
tim e
4
4 - f t d iam eter
d iam eter,
is
198 0
an ten n as
g iven
by
a
„•
th e
an ten n as.
d ata
co llectio n
in
«
and
and 8- f t . d i a m e t e r
p arab o lic
i
th e
’
irf
The .re c e iv e
d ia g n o stic : system p a ra m e te rs
to
is
'
an ten n as . used
resp ectiv ely .
2-ft
(ADC).
sig n a l
a c q u i s i t i o n . sy stem
d u rin g
of
*
,
1981
p arab o lic
bo th
cases
A sum m ary o f
in A ppendix
th e
2.
3.3 The Data Acquisition System
3 .3 \1
G eneral D e sc rip tio n
.
*
■
A d a t a ^ a c q u i s i t i o n s y s t e m w a s a s s e m b l e d ‘t o c o n t r o l t h e
,dE!
‘
c o llectio n
of
d ata
from
the*' d i a g n o s t i c
s y s te m and i t s
*
*
*
subsequent
reco rd in g . on
m ag n etic
tap e.
H igh
sto ra g e
.
>
>
c ap acity ,
for
d ata
re lia b ility
in
a c q u isitio n
'
fie ld
in
o p eratio n s,
o th er
t h a t w ere
fo llo w ed
in
m
'1
To accom m odate' th e
larg e
•
M Byte • p e r
w ith o th e r
m ag n etic
day,
com pute?
tap e
th e
th e
sy stem .
«
a ’J n o u n t o f . < J a t a
'
1 .2
•
th ed esig n o f
are
it
-
*
a d a p tab ility
ex p erim en ts
t
.
g u id elin es
and
( ap p ro * im ately
•
8 b i t p e r b y te ) and f o r c o m p a t i b i l i t y .
I
i n s t a l l a t i o n s . , th e d a ta i s re c o rd e d
on
u sin g
a 9 -track
L ":
d ig ita l, tap e
'
recorder.
The
t
reco rd in g
d en sity
is
800
b&i
and
th e
tap es
are. re c o rd e d
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
in 1
IBM-NRZI
form at
which
com putet i n d u s t r y .
•capable
of
used
w idely
throughout
Using *2 4 0 0 - f t
tapes,
the
providing
is
the /
system
u n in terru p ted recording of data
is
fro m
t h e d i a g n o s t i c s y s t e m f o r more t h a n t e n day .s. . F u r t h e r m o r e ,
the
system
is
capable
of
auto m atically
r e c o r d i n g ^ p r o c e s s on p o w e r - q p
'
in
the
resum ing
event
of
a
the
po we r
failu re.
ti
■
1
•
.
•
f
I' *
"
System C o n f i g u r a t i o n
3 .3 .2
•
The c o n f i g u r a t i o n o f t h e d a t a
?
,
shown
in F ig .
3.7.
\
a c q u i s i t i o n ' system
The h eai/t o f t h e s y ste m i s
is
a- S - 1 0 0 Bug ^
o r i e n t e d microcomputer- t h a t c o o r d i n a t e s t h e d a t a c o l l e c t i o n
»
'
\
and
recording
processes.
The
s t a n d a r d S - 1 0 0 S y s t e m Bus
•carries a ll
t h e a d d r e s s , d a t a , , a nd s f a t u s s i g n a l s , a s ’ w e l l
•
U
• * *
c
as th e u n re g u la te d supply v o lta g e s .
The C e n t r a l P r o c e s s i n g
■ <»
'
U n i t (CPU) i s b a s e d on t h e I n t e l 8080 m i c r o p r o c e s s o r
=and
.*
C,
.*
■
•*
is
operated
a t a clock r a te of 2
The u s e r i n t e r f a c e
' •
\
*
t
t
|
f o r b a s i c computer o p e r a t i d n s
I:
*
E<;
r
r
fs
|
✓-
|
‘
’
e•
'
p a n e l s w i t c h e s and CPU s t a t u s i n d i c a t o r l i g h t s .
i
*
.
•
S y s t e m memory c o n s i s t s of° 16K o f . Random A c c e s s
and
4K
of
Erasable-Program m able
Memory
Rea d O n l y Memory
*
_
m
*
I
I
| v
i s p r o v i d e d by a s e t o f f r o n t
-
(RAM)
l
,
(EPROM).
The b a s i c m a c h i n e / s o f t w a r e c o n s i s t s o f a
m achine
.
m onitor
program
t h a t o c c u p i e s 3K o f EPROM and was a d a p t e d
from
m onitor
program
a
^
developed
*
for
use
on
another
.
‘
I n t e l 8080 b a s e d m i c r o c o m p u t e r
acq u isitio n ,
«
recording,
•
[ 2 7 ) . - To im p le ifte n t t h e d a t
and d a t a t a p e f o r m a t t i n g f u n c t i o n s ,
&
<
ad d itio n al
softw are
Was d e v e l o p e d
w hich
o c c u p i e s IK o f
i.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
CLOCK
NTEL 8080
RAM
EPROM
l/>
3
CD
o
Computer front
panel switches. &
statu s indicators
p
i
CO
M,--------------=
-------
2
!/o
U J :-------- :------- .—
CO
>"
CO
■<------------------------
Microwave
Diagnostic
*
a
--------------------------
■<------------ —------
--------------------- ► Vo ------- 1---------------
----- 1~
—
Vo. -------4 ‘ e---------- --------------- ►
fr
ti
3.7
CIPHER
% - track digital
tape recorder
>
-- ------- • ---- ^
Fig.
—
..
TTY
Vo
<*
. Auxiliary
Status
Display Panel
C o n f ig u r a tio n o f th e D ata A c q u i s it i o n
System .
- »
{
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
51
EPROM.
A memory map f o r
th e m icrocom puter system is
shown
i n A ppendix 3.
In te rfacin g
m icrocom puter
between
is
extern al
provided
serial
in p u t-o u tp u t
p o rts
are
used
(I/O)
for
by
a
p o rts.
equipm ent
number
and
the
o f p a r a l l e l , and
Two c o m p l e t e p a r a l l e l I / O
d a ta com m unication w ith ,
and f o r
the
p
control
of,
the
asynchronous
9 -track
serial
I/O
d ig ital
p o rt,
term inal
'a u x ilia ry p a r a lle l
or
telety p e.
in terfacin g
system f u n c t io n s
tape
to tal
not
recorder
t h e . m icrow ave
^
am plitude, phase,
ad dition,
and
diagnostic
and s t a t u s . .
The i n t e r f a c e w ith
a
In
an
-> ‘
an
I/O p o r t i s r e s e r v e d f o r m anual o v e r r i d e
and t h e d i s p l a y o f v a r i o u s
was
An
.
e x te rn a l video
board
recorder.
is used fo r
f
req u ires
tape
d iagnostic
system
V--.i
of
eight
p a r a l l e l input p o r ts for
and t i m e d a t a .
av ailab le
S in c e such
an
a t reasonable c o s t,
c o m p a tib le i n t e r f a c e board
was
co n stru cted
to
the
in terface
a S - 1 0 0 Bus
im plem ent
th is fu n ctio n .
t '
t;
A
summary
»
m icrocom puter
of
the
I/O
port
allp catio n s
i s g iv e n in Appendix 3.
m anufacturers th a t supplied th e
v arious
A lso,
in
the
a l i s t of the
component
d e s c r ib e d above i s in c lu d e d .
S'
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
boards
52
3.4
T h e D i g i t a l Ra&io
*
. v_
r
t
3 .4 .1
G e n e r a l D e s c t i p t io'n
A com m ercial
d ig ital
DRS- 8
d ig ital
k.
•
* ( ^
radio
was
u s e d , in
the
1981
ra d io experim ent.
D ig ital
Telecom .
The
Radio
The RD-3 r a d i o +i s a ' j o a r t o f t h e
*
“
System m a n u f a c tu re d
by •, N o r t h e r n
radio
operates
i n t h e 8 GHz f r e q u e n c y b a n d
and was d e s i g n e d t o c a r r y a 9 1 . 0 4 M b/s b i t
strdam
( tw o .DS-3
\
«
'
b it
stream s
of
4 4 . 7 3 6 Mb/s
each)
a
(RF
channel.
ap p licatio n s,
th is
i s e q u i v a l e n t t o 1344 PCM v o i c e c h a n n e l s
per radio channel.
The m o d u la tio n employed in t h e r a d i o i s
pro v id es
P a rtia l
a sig n allin g
The d i g i t a l
both
space
telephone
40 MHz
bandw idth)
Q uadrature
F or
over
Response
S ignalling
r a d i o was
p ro te cted
and f r e q u e n c y d i v e r s i t y
(Main
associated
com biner.
P ro tectio n
RF
and
(QPRS)
and
it
outages
by
speed of 2 b /s/H 2 .
again st
techniques.
d i v e r s i t y p r o t e c t i o n . i s p r o v i d e d by two
antennas
tran sm issio n
v ertic ally
D iv e rs ity antennas)
sectionrs
spaced'
to g e th e r w ith th e
adaptive
in-phase
IF
'
>’
F o r f r e q u e n c y d i v e r s i t y p r o t e c t i o n , t h e Main and
channel
and
The sp a c e
an
frequencies
used
in
the
te st^
are
7 . 7 8 6 1 1 GHz
and
7 . 8 6 7 5 9 GHz.
In
the
experim ental
"
f
c o n f i g u r a t i o n , t h e r a d i o had th e a d v a n ta g e o f a l x l
system
(one
Main
system ,
and
one P r o t e c t i o n c h a n n e l)
b u t in a developed
t h e one p r o t e c t i o n c h a n n e l w i l l
I
be
used
for
the
s
p r o t e c t i o n o f up t o f o u r r e g u l a r . c h a n n e l s .
The im provem ent
i n p e r fo r m a n c e due t o f r e q u e n c y d i v e r s i t y w i l l
t h e r e f o r e be
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
less
in
a
fu lly
developed
s y s t e m t h a n :t h e e x p e r i m e n t a l
co n fig u ratio n .
T h i s p o i n t s h o u l d b e b o r n e i n mind
in terp retatio n
of
the
r e s u l t s ' from
the
in
d ig ital
the
radio
experim ent.
/
3 .4 .2
Equipm ent D e t a i l s
F o r the*° p u r p o s e o f
used
for
the ex p e rim e n t,
m odulating
the
the baseband s ig n a l
tran sm itted
sig n al
P s e u d o - R a n d o m . B i n a r y S e q u e n c e p r o v i d e d by * a
Data
G enerator.
diagram
a
Pseudo-Random
The e x p e r i m e n t a l r e c e i v e r eq u ip m en t b lo c k
i s shown i n F i g .
essen tially
is
3.8 .
The' r a d i o
id e n tic a l receiv ers
for
co n sists^ of
two
t h e Main and p r o t e c t i p n
channels,
W ithin each o f
the
receiv er
channels,
the
two
RF
«
sig n als
1
f r o m t h e M ain and D i v e r s i t y a n t e n n a s a r e c o n v e r t e d
t o IF and
c o m b i n e d by an a d a p t i v e
in-phase
com bined
s ig n a l^ is
equalizer
and an a d a p t i v e l i n e a r
equalizes
iri-band a m p litu d e s l o p e s .
J ^ e n 4 co n ditioned
by
am plitude
com biner.
The
a li n e a r delay
eq ualizer
.T his r e s u l t i n g
th at
sig n al
'
\
'
i s • s u b s e q u e n t l y d e m o d u l a t e d by a d i g i t a l d e m o d u l a t o r ' .
f
*
'
*
,
^
sThe o u t p u t . b i t . s t r e a m frdm
t h e M a in a n d P r o t e c t i o n
•* '
’
*
"
Channel
dem odulators
a r e ’ f e d ’, t o
a CE-4B A u t o m a t i c
t
i
•
P r o t e c t i o n Sw itch
w h i c h c o n t r o l s -the
sw itching
of
the
*
*
*
sig n al
betw een ‘ th e
M&in and P r o t e c t i o n c h a n n e l s .
One o f
*
*
the
DS-3
sig n als.. (co n sistin g
of
the
transm itted
• . 1
pseudo-random
for
1 .
. . .
d a t a N sejqilarfce)
,
the purpose o f
.
tKe,
.f r o m t h e P r o t e c t i o n Switich,
experim ent,
. -
w^s * m o n i t o r e d
i
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
by. a
R eproduced
with perm ission
*>
*
of the copyright ow ner.
#
7.78611
GHz D.C.
Further reproduction
7.86759
GHz D.C.
D iversity
Com biner
Digital
Demodulator
Diversity
Com biner
v
Linear
DelayEqualizer
Adaptive
Equalizer
prohibited
■o
without p e rm issio n .
7.86759
GHz D.C.
UJ
D ig ita l
Demodulator
c_>
Diversity A nt. AGC
I
Main A nt. AGC-
DS- 3
• S pectrum
Analyser
Data Recording
Equipm ent
HP 3782
BERT
ui
c.>■
in
cc
*■ O.C.- Down Converter
Fig. 3.8
Block diagram of the Digital Radio Receiver.
<T
€-
U1
55
)
H ew lett
Packard
model
perform ed B it- E r ro r - R a te
A l s o shown i n F i g .
were
m onitored
p a r a m e t e r s ^ wer e
(in c lu d in g
the
t h e IF S p ectru m ,
the
in
H P - 37 82
Error
3.8 a r e
obtained
th e v a r i o u s p a ra 'm e te rs t h a t
from- t# e
D iv ersity ,
Most o f t h e m o n i t o r e d
P ro tectio n ,
channel
and Co mbined AGC l e v e l s ,
the adaptive e q u a liz e r s tr e s s v o lta g e ,
v
-> *
d e m o d u l a t o r Eye V o l t a g e )
in ord er to e lim in a te
e f f e c t s on thej^Main f r e q u e n c y c h a n n e l .
Main
w h ic h
i,
( B E R ) " m e a s u r e m e n t s on t h e s i g n a l .
the experim ent.
M ain,
D etector
c h a n n e l Eye V o l t a g e ,
in
and
loading
addition,
-
*the
t h e S y n c - l o s s , ' and t h e "BER^flibnt
•tA"
■*
were a l s o r e c o r d e d .
* C;
%*
T he d a t a r e c o r d i n g e « ^ i ip m e n t c o n s i s t e d o f a low s p e e d
*
(1 mm/min) 4 6- c h a n n e l
paper
c h a r t *-recorder
a nd
a
'*
*
m ic ro p ro cesso r leased-m agnetic ta p e d i g i t a l r e c o rd e r.
The
■
^
Or
paper
chart
re c o rd e r p ro v id e d c o n tin u o u s re c o rd s o f the
a b o v e - m e n t i o n e d AGC l e v e l s ,
adaptive
eq u alizer
.S tress
t h e two Eye V o l t a g e s ,
V oltage.
'
\
j
the
D u r i n g p e r i o d s when
o u t a g e s w ere o b s e r v e d , t h e s e p a r a m e t e r s ,
S yn c-lo ss,
and
to g e th e r w ith
the
'
¥
BER,, and t h e IF S p e c t r u m , w e r e r e c o r d e d on t h e
>
.
m agnetic tap e d i g i t a l r e c o rd e r w ith a h ig h e r r e s o l u t i o n .
The a n t e n n a s u s e d i n t h e d i g i t a l
r a d i o e x p e r i m e n t were
1 2 - f t p a r a b o l i c a n t e n n a s t h a t h a v e a m t e n n a g a i n s o f 4 6 . 8 dB.
The a n t e n n a b e a n r w i d t h s a 't 8 GHz a r e 0 . 7 3 d e g
betw een
3 dB—
f
p o i n t s o r 1 : 1 7 deg b e t w e e n 10 dB p o i n t s .
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Chapter 4
THE PROPAGATION EXPERIMENTS
4.1 > in tro d u ctio n
The Bay p f Fundy i s
*
separates
-the
*
Scotia
-
50 km
wide
opean
in let
provinces
of
New
Brunswick
In a d d i t i o n to b e in g * n oted
»
tid es
(NB)
and Nova
for
having
in . t h e
w orld,
it
i s a l s o known t o r a d i o
A
outages
1
'
on
o-
LOS
?
t
*
naf&nown
the
p ath ..
m icrowave com m unication s y ste m s
i n s t a l l e d on p a t h s a c r o s s t h e bay w er e
to
the
-}
e n g i n e e r s a s a> p a r t i c u l a r l y " d i f f i c u l t " , p r o p a g a t i o n
Frequent
th at
' '
(N§).
highest
a
.»
u sually
attribu ted
^
*
or anomalous p r o p a g a t i o n c o n d i t i o n s .
fading
mechanisms
topographical
featu res
«Nere
and
not
w ell
A lthough
understood,
the m eteo ro lo g ica l c o n d itio n s
a s s o c ia te d w ith th e m aritim e c lim a te 'w e r e R e l i e v e d to
given r is e
the
to th e se p ro p a g a tio n anom alies.
have
.
Two f t i c r o w a v e p r o p a g a t i o n e x p e r i m e n t s
acro ss - the
wer e c o n d u c t e d
♦
Bay o f F undy d u r i n g 1980 and 1981 t o s t u d y t h e
p r o p a g a t i o n m e c h a n is m s a s s o c i a t e d w i t h m ic r o w a v e f a d i n g ^
«/.
on
f
LOS
lin k s.
In
addition
to re a s o n s m entioned above,
the
c h o i c e o f t h e Bay o f Fundy a s t h e - s i t e f o r t h e e x p e r i m e n t a l
study
was
further
T e l e p h o n e Company
telep h o n e
Company
p r o m p t e d by p l a n s i n t h e New B r u n s w i c k
(NB.Tel)
and t h e M a r i t i m e
(M.T.& T)
T elegraph
and
t o i n s t a l l a wideband d i g i t a l
r a d i o s y s t e m a c r o s s t h e bay a s a p a r t o f
the
Trans-C anada
56
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
57
T elephone
System
(TCTSJ.
The s u s c e p t i b i l i t y o f wideband
fc d ^ g i ta l r a d i o s y s t e m s t o p r o p a g a t i o n
known
[2 8 ], • [29].
Ir\
a
d isto rtio n s
route ' across
the
th,e
propagation
cond itio n s,
rad io in s ta lle d
on
Bay o f Fundy was u n a c c e p t a b l e d u e t o
unknown p r o p a g a t i o n d i s t o r t i o n s
of
w ell
t e s t p e r f o r m e d i n 1 9 7 9 , i t was
found t h a t the p erform ance o f a d i g i t a l
a
is
[30].
mechanisms
p articu larly
A
b etter
during
regarding
knowledge
severe
th eir
fading
effects
on
*
w ideband. d i g i t a l ra d io sy stem s, t h e r e f o r e
is needed.
The f i r s t e x p e r i m e n t was p e r f o r m e d d u r i n g
J
f ro m
5 th Septem ber to 3rd November,
path
was*
F ig.
4.1)
from
A y l e s f o r d , NS
to
1980.
period
from
The p r o p a g a t i o n
O tter
L a k e , NB
(see
and t h e e q u i p m e n t u s e d was a m i c r o w a v e d i a g n o s t i c
x s y s t e m w h ich w a s * - d i s c u s s e d i n C h a p t e r
3 1 st.Ju ly
experim ent
was
, propagation
to
3.
3rd Septem ber,
conducted
on
D uring the p e r io d
1981," th e
a
slig h tly
second
d ifferen t
p a t h f ro m O t t e r L a k e , NB t o N i c t a u x S o u t h , NS.
f
'I n
the
4
a d d i t i o n to th e d i a g n o s t i c system ,
a d ig ital
r a d i o * was.
in stalled
by
the
telephone
c o m p a n i e s and o p e r a t e d
11 «
»
s i m u l t a n e o u s l y on an e s s e n t i a l l y i d e n t i c a l p r o p a g a t i o n p a t h
i
in t h i s second e x p e rim e n t.
*
• T his , chapter
describes
d etails.
•*
the
v arious
*
experim ental
The c h a r a c t e r i s t i c s o f th e p r o p a g a t i o n p a t h s a re
d is c u s s e d w ith re fe re n c e
to - the
path
p ro files
and
the
average
m eteorolog ical, co n d itio n s
in
the
region.
The
*
r e c e i v e d s i g n a l c h a r a c t e r i s t i c s under normal c o n d i t i o n s a r e
/
p red icted
based
on
the
above
co n sid eratio n s.
\
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
In
R eproduced
with perm ission
of the copyright ow ner.
Brunswick
P.E.I.
M oncton
Further reproduction
O tt« r Lake
Stint JohnV) *
prohibited without p e rm issio n .
Bay of
Fundy
Truro
Xs^Ayleslord ^
NlCtAux S o u th
((H a lifw
A tlantic
4.1
Ocean
The propagation paths across the Bay of Fundy
Ul
00
59
S e c tio n 4.4 v a r i o u s a s p e c ts of th e
are
d iscussed,
as
data
an alysis
w e ll as the a c c u r a c i e s of
process
the ray p a th
p a r a m e t e t e s t i m a t e s - o b t a i n e d from t h e svjeep f r e q u e n c y d a t a .
"
,
f
'
r
tr-
4.2
T h e P r o p a g a t i o n P a t h i n t h e 1980 E x p e r i m e n t
f
‘
• . t
■
T h e - p r o p a g a t i o n p a th in t h e
1980 e x p e r i m e n t , i s
an
:
•' *
o v e r - w a ^ e r p a t h o f l e n g t h 80 .025 km ( s e e F i g . 4 . 1 ) b e t w e e n A y l e s f o r d and O t t e r L a k e .
A m a j o r p o r t i o n -of t h e t e l e p h o n e
v o i c e t r a f f i c b e t w e e n t h e A t l a n t i c c o a s t and o t h e r p a r t s o f
»
i
C a n a d a i s c a r r i e d on 4 GHz n a r r o w b a n d
'i
analog
radio
lin k s
e s t a b l i s h e d on . t h i s , p a t h .
The same p a t h Was p r o p o s e d t o . be
*.
*
i n c l u d e d a s p a r t o f t h e TOTS d i g i t a l
n$twor,k.
A d ig ital
]i
radio
test
was c a r r i e d
out
in
1979 b y . t h e t e l e p h o n e
com panies to d e te rm in e
d ig ital
r a d i o on t h i s
the
feasib ility
link.
The r e s u l t s
of
in stallin g
in d ic a te d t h a t the
d i g i t a l r a d io did not p ro v id e a c c e p ta b le perform ance
0
in
[3fl].
D e ta ile d p a ra m e te rs o f the p ro p a g a tio n p a th a re
Appendix 4
together
w ith
refractiv ity
t o K => 1 . 3 4 ) .
reflected
conditions.
and
the
a *■
given
path - p r o f i l e i s shown i n F i g .
4.2
the
r a y . p a t h s dr aw n " t o r
a.
co n stan t
•
*
g radient,
d N / d h , of- - 4 0 NU/km ( c o r r e s p o n d i n g
Two s t r o n g r a y p a t h s — a d i s e c t and
ray,
are
possible
A lthough p o t e n t i a l
at'
l e a s t ., u n d e r
t e r r a i n blockages
s e a r e f l e c t i o n e x i s t a t two p o i n t s
a
sea
normal
for
the
along th e p a th ( p o i n t s A
and B a t 3 . 4 5 and 16.85 km from O t t e r
Lake
respectively)/
r.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
60
o
00
JC
o
o
33
O
\£>
.6
O
J5 X
rv a.
CN
cn
O
o
o
*
co
Lf)
O
O
o '
• O
O
° >< >. o
n o: , eg
1SW 3A0qD'{uJ) 1L|6!3H
f'
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
they^
are n o t e f f e c t i v e under normal c o g n i t i o n s .
Including
*
an a v e r a g e t r e e h e i g h t p f 12 ta f o r t h i s ' g e o g r a p h i c a l
area,
*i r*
-
th e .
elevations
of the blockage p o in ts
a b o v e mean s e a ' ^ l e v e l . (MSL) .
- 4 0 NU/km
a
normal
gradient
of
and a t a f r e q u e n c y o f lt^-GHz, t h e ' c l e a r a n c e s f o r
th e sea r e f l e c t e d
- 0 . 3F j
For
a r e 25^ m and 134 m
and
ray a t
0.5Fi
t h e s e L o c a t i o n s w ere e s t i m a t e d
r e s p e c t i v e l y , where F / i s
as
t h e . r a d i u s 1o f
t h e f i r s t F r e s n e l Zone a t t h e c o r r e s p o n d i n g p o i n t s ,
Before f u r th e r
resu lts
f r o m r a y t r a c i n g are* d i s c u s s e d ,
one q u a n t i t y o f \m p io rta n c e i s t h e e x p e c t e d pange o f dN/dh
®
*
values for th is
geographical
area.
In e s tim a tin g
th is
range,.
use
was
made
of ^published
values
T*ropos^heric R ^ £ * £ c t i v i t y A t l a s f o r Canada
p ro b ab ility
d istrib u tio n
curves '
of
[3] .
the
from
the
S ince
the
refractiv ity
%
g r a d i e n t w ere n o t a v a i l a b l e
values
w er e
nearby
locations;
I s l a n d , NS.
p ro jected ,
for» th e
Bay o f . F u n d y ,
the
*'
using
the
d a t a , a v a i l a b l e f o r two
nam ely,
■
these
99.8 ^
an<l
S able
The s e a s o n a l d i s t r i b u t i o n s o f b h e ^ r e f r a c t i v i t y
V
g r a d ie n t fo r .these lo c a tio n s
on
P o r t l a n d , Me ,
published
of
.
a r e shown i n F i g .
values,
the
- 3 4 0 < dN /dh <‘ 245 NU/km
4 .3 .
'
Based
t h e r a n g e o f d N / d h v a l u e s f0'r
tim e
during
was
estim ated
_
as
th e p e r io d from Septem ber
/
4
t h r b u g h November.
*
A l s o a v a i l a b l y .from t h e same s o u r c e
the seaso n al v a r i a t io n s of th e s u rfa c e r e f r a c t i v i t y
above l o c a t i o n s
*
'
are
fo r the
and t h e s e a r e shdym i n F i g . 4 / 4 .
B a s e d on
«
.
‘
-, > .
t h e s e ' s t a t i s t i c s , an a v e r a g e s u r f a c e r e f r a c t i v i t y v a l u e o f
- ,
340 NU i s
1
.
*
as su m ed f o r t h e Bay o f F u n d y .
;
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
*
6 2
(a) Portland, ME.
-L-t-f- i .i i
i
i , i
i t t i i
i
i
i
l. j
,i j n
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-9 0 0 -
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(b) Sable Islands NS.
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M.M '
V
*z --height above ground
F ig . 4. 3
, •
j
S easonal p ro b a b ility d is tr ib u tio n o f
J* ground-based r e f r a q tiv ity gradients’ fOtr
■' CaT Portland
. , and (b) Sable Island',
.
[31,. ■
^
f
;
**
•*
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
380(a)
360-
340-
95% range
3
5*
'320H 7 7 T T f / /,*/v
>»
>i r / /
/>
A
< / / / / / / > ,
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j
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n u '/ i L
>>, J / / /V
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cu
m ean
•
£K 2 8 0 -
dry component
260-
y
240-
%
T
M
A
A
M
T
S
T--------1— T T
J
J
A
PORTLAND, ME.
N
380-
(b)
si, / / / / / ,
360-
340-
9 5 % range
'//>
O
z
f
320- ^ 7 7 7 '" 7 7 /
»/ / / / / / / / 11
>f /f /I/ t/ /• /f /f• ’
">
_+■<
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3
/V
300-
.
/
m ean
* •
' U / 1/
' ^ I L l UC
O
a*
a: 280s-
260-
240-
y
/ /N
dry component
*
i ------- 1---- n — n------ 1— n -------- 1------ 1---- 5— r
F
M A
M
J
J
.A „ S
O
N
Sable island , ns.
F i g . 4 . 4 ^ s e a s o n a l b e h a v i o u r of, t h e s u r f a c e
♦
' r e f r a c t i v i t y f o r : (a) ^ P o r t l a n d , M e.,
,
a n d (b) S a b l e I s l a n d , N . S . [3J».
■ X
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
H a v in g o b t a i n e d a bound on t h e r a n g e o f
»
dN /dh
values
i
9
e x p e c te d in t h i s
area,
may- be d i s c u s s e d .
th ree
the r e s u l t s
f ro m f u r t h e r
ray tr a c in g
The r e s u l t s o f ray t r a c i n g p e rfo rm e d fo r
*
i
r e p r e s e n t a t i v e v a l u e s o f d N / d h a r e shown, i n F i g .
I t is
observed
reflectio n
values
is
th at
not
th e
terrain
blockage to
4.5 .
the
sea
e f f e c t i v e e x c e p t f o r . t h e more p o s i t i v e
of th e r e f r a c t i v i t y
"g rad ien t.
These r e s u l t s
are
v
summarized
in
F ig.
4.6
in
which
d irect
and r e f l e c t e d r a y s w e r e
w hile
taking
the
am plitudes of
estim ated
by r a y
t e r r a i n blockage;
account
a perfect
the d i f f r a c t i o n
the
tracing
9
in to
>
•
l o s s e s due t o
sea
reflectio n
and
the
d iffractio n
average’
ri
terrain
-assum ed.
ch aracteristics
at
F u r t h e r m o r e , s i n c e two
(p o in ts . A
o b stacles
p o i n t s were
were
involved
and B* i n ' F i e f . 4 . 2 ) , t h e d i f f r a c t i o n l o s s e s w er e
> e s t i m a t e d b a s e d on a p r o c e d u r e p r o p o s e d by D e y g o u t [31]
d ealing
w ith
m ultiple
knife-edge
d iffractio n .
a t t e n u a t i o n o f 20 dB a s t h e c r i t e r i o n ,
for
U s i n g an
th e blockage to
the
js£a re fle c te d
r a y i s a d e q u a t e o n l y f o r v a l u e s o f d N /d h l e s s
* . *
'
n e g a t i v e ; t h a n a p p r o x i m a t e l y - 3 5 NU/km.
*« '
*
.
I n a d d i t i o n t o t4re r a y p a t h a m p l i t u d e c h a r a c t e r i s t i c s ,
/th e
an g le-of-ajr r i v a l e s t i m a t e s ’ are,-also of im po rtance.
In' - '
'■ ..t h e
1980
at
!'
experim ent,
the
*
*
A ylesford
I
tran sm itter
arid
the
»
was ‘ l o c a t e d
,
receiver
*
®
art * O t t e r
Lake.
a h g l e s - o f - a r r i v a l a t O t t e r L a k e . a t e ' shown i n £ i g « * 4 . & .
m
j
' ' ‘ t*
The
By:
¥
applying £q. (2.9) 4he range in a n g le -o f-a rriv a l for 9f9 .8 - i
’ of the time was estim ated as 1,34 deg.
th is
(
la tte r
One consequence
of '
o b servation is t h a t ‘'a^U m it should be i&posed
A
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
(a)
Aylesford
Otter Lake
dN/dh =150 NU/km
400
»
,-0.72'
XI
-
0.68 '
XL
cn
T
T
T
1
T
■
dN/dh ? -HO NU/km .
-
*
0 .02 '
£200
XL
cn
T
T
TT
T
‘—T
T
T
dN/dh =-300 NU/km
-I
</)
0.35'
-026
£200
40
>
D istance
„ Fig.. 4.5
(km)
Ray Tracing--on A ylesford - p t t e r Lake, path fo r
th re e re p re se n ta tiv e values o f tshe r e f r a c tiv it y
g ra d ie n t.
^
,
v
ii/ ^ "■
1
r - -*
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
*
66
.
t
£
Effective Earth Radius Factor, K
-2
«
-10 so 10
2
0.5
1
«
/
S ' -30
»
D — Direct Ray
R — Reflected Ray
0—
15—
10—
5—
-200
-100
.
0
“
100
Refractivity Gradient, dN/dh (NU/km)
F ig.
4.6
Ray p a t h c h a r a c t e r i s t i c s f o r
A y l e s f o r d O t t e r liake p a t h u n d er
c o n d itio n s o f uniform r e f r a c t i v i t y
g rad ien t.
.
'
.
_
a
■
*
.
’
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
/
on t h e maximum s i z e (minimum b e a m w i d t h )
of
th e antennas
>
#
'
u s e d on t h i s p r o p a g a t i o n p a t h .
F u rtherm ore, sin c e the
d i f f e r e n c e in a n g l e - o f - a r r i v a l o f th e d i r e c t
' and
the
sea
a*1
reflected
0.25 deg,
rays
Under n o r m a l c o n d i t i o n s
angle d is c r im in a tio n
i s o f the^ o r d e r o f
(th ro u g h th e use
of
sim ple
/
narrow-beam-
antennas)
elim inating
carinot
be
effectiv ely
For a
^
normal
was
g radient
estim ated
to
.
of
be
«
- 4 0 NU/km,
the
roughly
received
co m p o se d o f a d i r e c t r a y - o f .
" n o r m a l " a m p l i t u d e a nd a r e f l e c t e d r a y f r o m t h e
is
for
the sea r e f l e c t i o n .
<
*
sig n al
used
sea
which
- 1 9 dB i n ' a m p l i t u d e r e l a t i v e t o t h e d i r e c t * r a y
( a n a v e r a g e t r e e h e i g h t o f 12 m was a s s u m e d
<
<
th is v alue).
The tim e d e l a y o f t h i s
in
estim ating
r e f l e c t e d ray r e l a t i v e
’
to th e d i r e c t r a y w a s e s t i m a t e d . a s a p p ro x im a te ly 2.5 n s e c .
4.3
The Propagation Path in the 1981 Experiment
*
• '
,
'-i
. ’
*
B a s e d on t h e r e s u l t s o b t a i n e d f r o m tfie 1979
| $
i
e x p e r i m e n t s , an a l t e r n a t e
c h o s e n and
1980
r o u t e a c r o s s t h e Bay o f Fundy was
ii^B s u i t a b i l i t y f o r i n c l u s i o n i n
in v estig ated
i n t h e 1981 e x p e r i m e n t .
from f O tter
Lake
to
and
Nictaux “ south
the
TCTS
was
The e x p e r i m e n t a l p a th
(see
F i g .-4^1)
is
8 0 . 3 7 5 km i n
length
and * t h e v a r i o u s p a t h p a r a m e t e r s a r e
*
'
shown i n A p p e n ^ . ? ^ .
The p a t h p r o f i l e , t o g e t h e r w i t h
the
/
4
i
*
’
.
ray
paths
dipawn
for , a co n stan t re fra tc tiv ity g ra d ie n t of'
-40 NU/km, is shown in F ig . 4 .7 .-,KOne of, the
main
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
reasons
;
Reproduced
with permission
of the copyright owner.
Otter Lake
. N ictaux South
dN/dh r -4 0 NU/km
Further reproduction
400
0.30'
-0.23'
o
XI
.*
V
-0.58'
prohibited without p e r m is s io n .
200
60
20
D is t a n c e
‘F i g ^
*
RX
0.61
4 .7 '
80
( km)
P a th p r o f i l e f o r t h e O t t e r Lake - N ic ta u x S o u th
p ro p ag atio n p ath .
68
69
for
the
choice
of
th is
blockage to the r e f l e c t e d
N o rth M ountain
propagation
ray.
The
( la b e lle d A in F ig .
path
is the b e tte r
blockage
4.7)
offered
b,y
h i s an e l e v a t i o n o f
179 m ( i n c l u d i n g an a v e r a g e t r e e h e i g h t o f 12 m) a b o v e MSL.
At
a
frequency^ of
10 GHz
for
a normal g r a d i e n t o f
- 4 0 * NU/km, t h e c l e a r a n c e f o r t h e
sea
*
’
o
*
l o c a t i o n was e s t i m a t e d t o be - l . O F j .
reflectio n 'a t
1
The r a n g e o f d N / d h v a l u e s f o r 9 9 . 8 % o f t h e
th is
path
is
expected
A ylesford - O t t e r
the
average
e jf p e r im e in t
Taking
range
into
. in
be
sim ilar
to
th a t for
for
the
L a k e p a t h a nd t h e same s h o u l d be t r u e f o r
surface
was
to
tim e
th is
refractiv ity .
perform ed
account
dN/dh
during
the
However,
the
m onth
the
of
seasonal v a ria tio n s ,
1981
A ugust.
th e 99.8 %
was
e s t i m a t e d , from
F i g . 4^3
as
*
c
*
- 4 3 0 <; d N / d h < 260 NU/km.
A gain,
ray
tracin g
for th ree
- *
♦
r e p r e s e n t a t i v e val<ues**mf d N / d h a r e dfcown i n * F i g . 4 . 8
from
w h i c h i t may be o b s e r v e d t h a t N o r t h f o u n t a i n
b etter
blockage to th e
summarized
in. F ig .
reflected
4.9
which
ray.
was
The
does p ro v id e a
resu lts
are
derived
in a s im ila r
*
manner a s f o r F i g . 4 .6 p r e s e n t e d f o r th e A y l d s f o r d O tter
*
Lake p a t h ,
although
in # t h i s
case
there
i s , o n ly oqe
o
,
d iffractio n
c rite rio n
reflected
point
of.
.at
20 dB
N orth
fo u n tain .
atten u atio n ,
U sing
the
th e blockage to th e sea
ray i s a d e q u a te f o r v a l u e s o f dN/dh g r e a t e r ,
- 1 0 5 NU/km.
’
same
,
than
’
As f o r t h e r a y p a t h ' a n g l e - o f - a r r i v a l c h a r a c t e r i s t i c s
.
*
. *• '
a t the re c e iv e r s i t e a t N ictaq x S outh, the p r e d ic te d v a lu e s
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
70
t
-
O tU r
Lata
Nictaux S
dN/dh =150 NU/km
400
$
-0.74
300
-0.67
200
100
dN/dh«-140 NU/km
J400
-0.07
OOO!
• 300
-0.40
200
100
T
T
T
r
0.37
200
&
40.
O U tanca
Pig.
4.8
(k in )
Ray T r a c i n g o n t h e Ott er * Lake - N i c t a u x § o u t h
, path fo r th re e re p re s e n ta tiv e values o f th e
r e fra c tiv ity grad ien t.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
71
Effective Earth Radius Factor , K
-2
-10»10 > 2
1
05*
V
> a
E .-W
5« - »
■
I
■*» -
O -j—Direct Ray.
R — Reflected Ray,
-0 J
15 —
10 *5 —
-200
-100
0
100
Refractivity G radientdN /dh (NU/km)
F ig.
4.9
Ray p a t h c h a r a c t e r i s t i c s f o r t h e O t t e r
. Lake - N i p t a u x Soiithi p a t h u n d e r c o n d i t i o n s
o f .uniform r e f r a c t i v i t y g r a d i e n t .
)
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
72
a r e shown i n F i g .
99.8 %
4.9 .
A gain
by
applying
the
r a n g e i n m a i n r a y a n g l e - o f - a r r i v a l was .e & c im a te d a s
1.6 d e g .
betw een
A lthough
the
the d i r e c t
difference
and s e a r e f l e c t e d
0.35 ^eg under normal c o n d i t i o n s )
for
Eq.
is
in
aftg& e^of-ar-rival
rays
{of th e o r d e r o f
l a j q e ^ than th e
value
.«V
A y l e s f o r d - O t t e r La ke p a t h * a r i g l e d i s c r i m i n a t i o n
the
j
.
i s s t i l l n o t u s e f u l f o r e l i m i n a t i n g i£ h e s e a r e f l e c t i o n .
The r e c e i v e d s i g n a l f o r a n 8 ^ a l g r a d i e n t o f - 4 0 NU/km
for
t h i s p ro p a g a tio n path
d ire ct
i s e s t i m a t e d t o b e co m pose d o f a^
r a y o f n o r m a l a m p l i t u d e and a r e f l e c t e d
roughly
- 3 0 dB
in
am plitude
w ith a tim e d e la y betw een th e
\
t
4.5 n s e c .
The
two
\
larg er
delay
e x p l a i n e d by t h e h i g h e r
elev atio n s.
■
4.4
*
relativ e
to the d i r e c t ray,
rays
v alue
tran sm ittin g
r a y which i s
of
in
approxim ately
t
th is
case being
and r e c e i v i n g
antenna
/
Data A n aly sis.
♦
i
^
'
4 .4 .1
D a t a fro m t h e P r o p a g a t i o n E x p e r i m e n t s
B e c a u s e ;o f
av ailab le,
the
the
large
volume
of
-e x p e r i m e n t a l
raw
d a t a t a p e s from t h e f i e l d e x p e r im e n ts
w e r e o r g a n i z e d and r e f o r m a t t e d i n t o r a n d o m - a c c e s s f i l e s
<r
* a
r
^
PDF-IO''
com puter,
o n ’ which*
a n a l y s i s work was p e r f o r m e d .
the
, T his
*
m ajority
data
on
of th e 'd a ta
fa c ilita te s
the
easy
. . access
a nd f a s t r e t r i e v a l o f . t h e d a t a s i m p l y b y s p e c i f y i n g
^
"**
&
*
*
the a p p r o p r ia te tim e inform ation.*
* . '
'
«
i
.
' r'
.
•
*
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
\
/
i
As
described
in
the
's e c tio n
on
the'
microwave
diagnostic
s y s t e m , t h e sweep f r e q u e n c y a m p l i t u d e and p h a s e
I
r e c o r d ^ do n o t g i v e
d i r e c t m easurem ents
of
the v ario u s
*
received
ray p a th p a r a m e te r s .
T h e re f o re , the p ro c e s s in g
o f t h e raw d a t a
inoludes a s p e c tr a l a n a ly s is
r
*
frequency
of
the
sweep
<9
am plitude
records
to
estim ate
the
ray
path
_
am plitudes,
and
r e l a t i v e ( delay
regression
an aly sis
of
the
tim e;
phase
and
a
lin ear
r e c o jrd t o e s t i m a t e
the
m a in r a y a n g l e - o f - a r r i v a l ' .
In u s in g
the
ray
th e s p e c t r a l a n a l y s i s method
path
am plitudes
p o i n t s s h o u ld be n o te d .
design
of
the
efficien cy .
.essen tia l
tria l
ro u tin es
in
the
a r e r e l i a b i l i t y and
involved,
is
on
these
s o fa s t o
p articu lar
[32]
m inim ize
requirem ents
runs u s in g d i f f e r e n t m ethods,
attached
app licatio n ,
is a s u ita b le choice.
it
is
it
com puting
and t h e r e s u l t s
was c o n c l u d e d
of
th at,
t h e Smoothed P e r io d o g r a m
A block o f
zeroes
is
t o e a c h 6 4 - p o i n t a m p l i t u d e r e c o r d and a 1 2 8 - p o i n t
FFT i s p e r f o r m e d .
the
a few i m p o r t a n t
co n sid e ratio n s
data base
an aly sis ro u tin e
Based
approach
„
data an aly sis
tinfe,
estim ating
t h a t r e l i a b l e and a c c u r a t p rcsttad - ts be p r o d u c e d by
for - the
I
The m ajor
Since a la r g e
an e f f i c i e n t
co sts.
and d e l a y
for
F requen cy averaging' i s
then *a p p lie d
to
s q u a r e d a m p l i t u d e s p e c t r u m t o g i v e t h e e s t i m a t e d 0 power
spectrum .
T his
frequency
averaging
is
necessary .
for
reducing
[32] ,
t h e e f f e c t s o f l e a k a g e - and t o r e d u c e t h I v a r i a n c e
>
j
[33] . T h e s e c o n d r a y A m p l i t u d e
and. d e l a y
tim e
is
*
•
obtained
*'
•*' ‘
from
*
th ^
'
power
"
spectrum* while
th e
*■
R e p r o d u c e d with p e r m i s s io n of t h e co p y rig h t o w n er. F u r th e r r e p r o d u c tio n p rohibited w ith o u t p e r m is s io n .
main
ray
am plitude
o rig in al
%
is
sw ee p r e c o r d
There
path
obtained
frofri-
the
(see F ig .
average'
3 .3 ).
value ’ of
t
*
.
i s ’an a d d e d c o m p l i c a t i o n ^ i n / e s t i m a t i n g
am p litu d es using
the
t h e a b o v e methfl^d.
In F i g .
the
3.3
ray
it
s e e n t h a t t h e sw ee p f r e q u e n c y a m p l i t u d e d a t a r e s u l t i n g
two r a y p a t h s a r e q u a s i - s i n u s o i d a l .
As a r e s u l t ,
m eth o d g i v e s v a l u e s
t h a t are not eq u al to
path
However,
am p litu d es..
the d e s ire d
above
it
the
is
from
th e above
actual
ray
i s shown i n A p p e n d i x 5 t h a t
r a y p a t h a m p l i t u d e s may b e
e s t i m a t e d v a l u e s by p r o p e r
obtained
scalin g .
f ro m
the
T his c o r r e c tio n
*
was i n c l u d e d
carefu lly
in th e
tested
*
resu lts
give
an aly sis
using
ro u tin e.
estim ates.
of
the
%
4.10(a)
errors
The l a r g e s t e r r o r s
are
which
also
in the a m p litu d e
involved
when
the
ray
,
f
are
close
and t h e d e l a y
am plitude
is
in am p litu d e
short.
However,
in
the
in th e d elay
(less
t h a n 3 dB d i f f e r e n c e )
«
The u n c e r t a i n t i e s
estim ates
+ 1 . 5 dB.
increases
and (b)
involved
0
paths
was
some o f t h e
**
*'
idea
ro u tin e
s y n t h e s i z e d ' d a t a a nd
a r e s u m m a r i z e d in F i g s .
an
The
such
cases
accuracy
in th e ray
are
im prpves
path
approxim ately
rap id ly
w ith
t i m e knd t h e d i f f e r e n t i a l ' a m p l i t u d e .
F o r e x a m p l e , when t h e T a ^ p a t h s d i f f e r
i n a m p l i t u d e lay more
t h a n 5 dB,.^the u n c e r t a i n t i e s i n t h e a m p l i t u d e e s t i m a t e s
are
l e s s t?h«m + 0 . 5 d B .
the
tests
'show
th at
As f o r
the
the
accuracy
delay*tim ed longer than 1.5 ns.
because
'*
of
lim ita tio n s
due
delay
tim e
is b e tte r
■I t
to
is
estim ate,
th a n + 0.1 ns fo r
also noted
th a t
i
a f i n i t e frequency sweep
range, ray paths with /delay times le s s
than
approxim ately
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
75
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,
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
*
' /
1 . 5 n s a r e -not r e s o l v e d .
~
• A few p o i n t s i n r e l a t i o n t o t h e a n a l y s i s o f t h e
phase
*
record
re q u ire d ; to produce
t h e m a i n t ^ y AOX a r e ' a l s o
»
•
\
W
'
notew orthy.
I t has been p o in te d o u t in C h ap ter 3 t h a t
the
main
,
ray
AOA
is
g i v e n by t h e g e n e r a l s l o p e o f t h e p h a s e
r e c o r d even in m u l t i p a t h s i t u a t i o n s .
th erefo re
involves
filterin g
Thea n a l y s i s
metho d-
the phase re c o rd
( t o remove
v a r i a t i o n s d ue t o t h e s e c o n d r a y )
and
estim atin g
from
the
slo p e o f
the
f i l t e r e d phase
t .
'
'
p e r f o r m e d on t h e a n a l y s i s r o u t i n e i n d i c a t e
record.
th at
AOA
e s t i m a t e d by t h i s m e t h o d i s b e t t e r
p r o v id e d t h a t th e second ray a m p litu d e i s
re la tiv e
t
AOA
T ests
main
'
t h a n + 0 . 0 5 deg
«
ray
the
the
l e s s than
the f i n i t e
- 1 0 dB
problem
la tter
when
p resen t.
A gain t h e
lim itatio n
was
imposed
by
f r e q u e n c y sweep r a n g e . c
T his
lim ita tio n ^presents
an
s h o rt delay ray p a th s ( le s s
The s l o p e o f
the p hase
record
even
g reater
th a n 0.5 ns)
is
are
sig n ifican tly
^ffooted
by e v e n
a low a m p l i t u d e s h o r t d e l a y r a y .
' 1
*
e f f e c t is
i l l u s t r a t e d in- F i g s . 4 . 1 1 ( a ) ' t o (d) i n w h i c h
am plitude
and
phase re c o rd s
are sy n th esized
co nditions for
the frequency range 0 t o
m onitored
the d ia g n o s tic
by
is a ls o in d ic a te d .
a
\
t o t h e m a in r ^ y and t h e d e l a y t i m e i s g r e a t e r t h a n
^approxim ately- 3 n s .
for
0
sin g le
shown f o r
syn thesized
Fig... 4 . 1 1 ( a )
sy ste m {from
w i t h two
ray p a th ^
the
for v a rio u s
Gpz. The
range
9 . 5 . t o ^ O . 5 - GHz)
sh o w s t h e a m p i i t ^ ^
r a y o f a m p l i t u d e 0 dB.
v a r i o u s AOA v a l u e s .
15
The
record
The p h ase r e c o r d
F i g s . 4 . 11(b)
to
(d)
is
were
o f a m p l i t u d e s 0 a nd - 1 0 dB.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
.
#
t
(b)
>
-20
f
OS
-20
360
360
o>
ot
-0.1
-0.2
0
5
10
Frequency (GHz)
o
15
5
10
15
Frequency (GHz)
sT = 0.06 ns
-20-
-20
•—**0S
t
360
360
£ 180
Frequency
IGHz)
Frequency (GHz)
OS-Diagnostic System sweep rartge.
F ig . 4.11
*
I
E f f e c t s o f s h o r t d e l a y r a y p a t h s on t h e sweep
f r e q u e n c y r e c o r d s ; t h e b r o k e n l i n e s s ho w t h e
id e a l phase rec o rd s i f th e sh o ^t d elay ray
path i s a b sen t.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
«
7 7
The main
>
and
second
ray
resp ectiv ely .
The
rela tiv e
0 .0 2 ,
- 0 .1 nf
0 .06,
a nd
resp ectiv ely .
The
sum m arized in
(broken
o btain ed
F ig.
are
delay
-0 .2
a n d ^ ^ 0 ~ . l d£g
o f t f e weaker p a th i s
forF ig s .4 . 1 1 ( b ) ( c ) ,
resu lts
4 .1 2 .
curves) ^ are
if
AOA's
showft i n
A lso
the
and
th ese
shown
in
fig u res
th ese
r e c o r d s w hich i d e a l l y
v a l u e g , 'h o w e v e r,
of less
ab sen t.
fig u res
s h o u ld be
*
It
th a n + 0.05 deg .
For t h i s
and i n t e r c e p t o f
the f i l t e r e d
p resented
in t h i s
S p u rio u s v a r i a t i o n s
th esis.
s
in
the
records
in
the phase
•
read ily
may
are
be
s i n c e t h e r e w i l l b e no c o r r e s p o n d i n g v a r i a t i o n s
in tercep t
in tercep t
re a so n , both
phase
r e c o r d s lo p e due t o s h o r t d e l a y ra y p a t h s
id e n tifie d
and in
o f t h e m a i n r a y AOA w i t h an
th e slo p e
/
is
a re pnly m ild ly a f f e c t e d
f a c t give a reaso n ab le estim ate
u n certain ty
is
i
are
seen
* '
th at
spurious
v a ria tio n s
in
the phase
record slo p e is
•n
i n t r o d u c e d by t h e
presence
of
short
d.elay
ray 's.
The
in tercep t
th e s h o r t delay path
(d)
v alu e.
is* r e l a t e d
to
It
is
also
.n o ted
th at
the
t h e m a i n r a y AOA by E q .
(3.2)
— a
**
%
5 9 . 7 d eg
change
in
corresp o n d s to a 0 .1
The a b o v e * e r r o r
v ariatio n s
the
in tercep t
v alue
at
d eg c h a n g e i n t h e m a i n r a y AOA.
bounds a re not
in th e v a r io u s
v alid if
o r when a, s t r o n g
short re la tiv e
is p r e s e n t . / The r e s u l t s
p rocessing
sig n ific a n t
r a y patjtii p a r a m e t e r s o c c u r
duratioY i d f a sw eep,
delay
r o u t i n e may b e e r r o n e o u s
The a c t u a l r a y
in th e
t h i r d ray pS th
w ith
from th e d a ta
in such c a s e s , b u t th e s e
e r r o r s c a n tie i d e n t i f i e d r e a d i l y from a t i m e | p l o t o f
param eter e s tim a te s .
9 . 5 GHz
path
the v a rio u s
p aram eters
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
may
- - c o r r e c t value
— estim ated value“
-
0.2
-
0.6
CL
~a
-
0.2
CL
180
-0.4
-
Phase
S’
0.6
0.10
Relative^ delay, a T . (ns)'
of su b sid ia ry ray
F ig.
4.12
record
360
*
intercept (deg)
CL
0.15
„
- '
*"
1
^ •
S p u r io u s v a r i a t i o n s i n e s t i m a t e d m ain
r a y AOA d u e t o s h o r t d e l a ^ s e c o n d r a y
p ath .
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
then
be
o b t a i n e d by u s i n g an i t e r a t i v e p r o c e s s o f p a t t e r n .
T
sy n th e sis as described p re v io u sly .
T his
latter
technique
«
'
may a l s o
b e u s e d t o j S b t a i n more a c c u r a t e e s t i m a t e s o f t h e
***r a y p a t h p a r a m e t e r s when d e s i r e d .
The a c c u r a c i e s
obtained
using
Such
a
technique are b e t t e r
and + 0 . 0 5 deg f o r
the r e l a t i v e
t h a n +1 dB, + 0 . 0 5 r i s e c ,
am plitudes,
relativ e
delay
t i m e , and t h e a n g l e s - o f - a r r i v a l r e s p e c t i v e l y .
•
►
*
4 .4 .'2
'
D a ta from t h e D i g i t a l R ad io T e s t
I
*
*
The d a t a s u p p l i e d by t h e - t e l e p h o n e
perform ance
were
the
records.
pn
the
The-
param eters
included
Main AGC, D i v e r s i t y AGC, a nd Co m bined AGC l e v e l s
*■
.
of the P ro te c tio n channel,
channel
com panies
o f t h e - d i g i t a l r a d i o a r e m a i n l y i n t h e form o f
lo w s p e e d p a p e r c h a r t
the
<•
Main
a nd
the
P ro tectio n
E ye, V o ltag es, ’ a n d t the a d a p tiv e e q u a liz e r S tre s s
^
/
V oltage for the p r o te c tio n ch an n el.
1
. >
'
'
T]ie m a i n i n f o r m a t i o n r e q u i r e d f o r t h e d i g i t a l
an
'
in d icatio n
of
its
radio is
e rro r p r o b a b ility perform ance.
For
«
t h i s purpose,
[35] .
T his v o lta g e
ey e d i a g r a m .
eye'
t h e eye v o l t a g e i s a s u i t a b l e p a r a m e te r
i n d i c a t e s t h e amount o f o p e n in g in th e
W ithout going i n t o e x c e s s iv e d e t a i l ,
d i a g r a m c o r r e s p o n d s t o an e r r o r
the o u tp u t o f th e dem oduratdr,
is
'v j
an
in d icatio n
[34],
free d ig ita l
an
open
sig n al a t
w h ile a c lo s e d eye
diagram
o f syst eir i d e g r a d a t i o n u s u a l l y c a u s e d by
i n t e r - s y m b o l i n t e r f e r e n c e . [34] .
Using th e eye v o l t a g e as
rebords
from
the
.d ig ita l
the
in dicatio n,
the- c h a rt
r a d i o t e s t were exam in ed .
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
The
•
t i m e p e r i o d s when e y e c l o s u r e s o c c u r r e d
propagation
data
iso lated
fu rth er
for
were
n oted.
o b ta in e d . d u r in g th e s e p e r i o d s were th e n
an aly sis.
*
'V -
,i
/
.
The
I
r
Jf
Reproduced with permission o f the copyright owner. Further reproduction prohibited without permission.
Chapter 5
MICROWAVE PROPAGATION ACROSS THE BAY OF FUNDY
*
4.
- AYLESFORD TO OTTER LAKE
5.1
In tro d u ctio n .
«
The r e s u l t s
presented
f r o m t h e 1980 p r o p a g a t i o n
experim ent
are
i n t h i s c h a p t e r and a r e e x a m i n e d w i t h r e s p e c t t o
th e s ig n a l c h a r a c t e r i s t i c s p re d ic te d
in
C h a p t e r 4.
Based
on t h e e x p e r i m e n t a l r e s u l t s , t h e m a j o r a s p e c t s o f m i c r o w a v e
\
p r o p a g a t i o n from A y l e s f o r d t o O t t e r Lake a r e d i s c u s s e d .
In o r d e r
proportions,
to reduce th e d a ta p ro c e ssin g
rep resen tativ e
from t h e l a r g e d a t a b a s e
t o ^m anageable
24-hour, p e r i o d s were s e l e c t e d
using'
the
availab le
continuous
••
analog
in
records.
th is
The r e s u l t i n g
way , w e r e
ch aracteristics
ch aracteristics
analysed
d a t a from t e n d a y s s e l e c t e d
to
produce
the
ray
path
o f t h e tw o s t r o n g e s t r e c e i v e d r a y s .
These
i n c l u d e t h e m a i n r a y a m p l i t u d e a nd AOA, a nd
4
t h e second ra y a m p l i t u d e and r e l a t i v e
*
d iscu ssio n s
d etailed
are
p resented
delay tim e.
only
A lthough
*
sele cted
for
r
periods
'it
|
c o n t a i n i n g s i g n i f i c a n t ' and r e p r e s e n t a t i v e r e s u l t s ,
is f e lt
t h a t a d d i t i o n a l i n s i g h t may
be
gained
from
c u r s o r y e x a m i n a t i o n .of t h e r a y p a t h c h a r a c t e r i s t i c s f o r
e n tire period.
*•
*
purpose th a t th e
I t is for th is
path
cl& ra cteristic s
fo r the e n t i r e
“
*
i n g r a p h i c a l form ' i n A p p e n d i x 6 .
'
te n days a re
1 - '
’
.
.
’
‘
-
8
m ajor
•
2
R e p r o d u c e d with p e r m i s s io n of t h e co p y rig h t o w n e r. F u r th e r r e p r o d u c tio n prohibited w ith o u t p e r m is s io n .
»a'
the
ray
included
5.2
G e n e r a l E x p e r i m e n t a l O bIs, e r v a t i o n s
In th d
first
diagnostic'
p ropagation
syst erti
experim ent
t h e ’ m icrow ave
w&s o p e r a t e d f r o m 5 t h S e p t e m b e r
y e a r * — 249) 1:o 3 r d November
(Day 3 0 8 ) .
(day o f
The f a c t t h a t
the
n
period
did
not
correspond
to
the
fading
seajpbn
^
,
u s u a l l y e x t e n d s f r o m May t h r o u g h A u g u s t )
ai s
the
fading
com paratively
. observed.4
*
m odest
. *r> *
.
amount
of
S
reflected
in
a c tiv ities
r
A cu rso ry exam ination of the c h a r t
during
the
experim ent
was
Tne g e n e r a l o b s e r v a t i o n i s
tim e
(which
ex h ib its
severe
co llected
p e r f o r m e d on an h o u r l y b a s i s .
less
th a t
fading
a p p r o x i m a t e l y 90 p e r c e n t - o f
records
t h a n 10 p e r c e n t o f t h e
activ ities.
F urth erm o re,
the observed fading
activ ities
o c c u r r e d d u r in g t h e month o f S e p te m b e r .
♦
A lth o u g h num erous e q u ip m e n t p ro b le m s were
encountered
*
d u rin g
the
e x p e r i m e n t , \a l a r g e
amount o f
data
was
«
co llected .
A rep resen tativ e
s e t o f d a t a from
10 d a y s
was.
<r
sele cted
as
the
d a t a b a s e . f o r t h e 19 80 e x p e r i m e n t .
T his
» .
‘
i n c l u d . e s d a t a c o l l e c t e d i n t h e b e g i n n i n g (Day 25 0 ) ,‘ i n
the
*
*
.
"•
m iddle
(Day 2 5 8 , 2 5 9 , 2 6 0 , 2 6 3 , 2 6 4 ) , a n d t o w a r d s t h e e n d
*
(Day 2 9 5 , 2 9 6 , 2 9 7 , 298) o f t h e e x p e r i m e n t .
,
»•;
*
fe'
'
1
Each hour i s f u r t h e r c l a s s i f i e d a s b e lo n g in g t o one o f
*
■A 9
*
'
t
‘
‘
two c a t e g o r i e s ,
nam ely,
n o h - f a d i n g d a t a and f a d i n g d a t a , *
«
*■
M ore s p e c i f i c a l l y , t h e f a d i n g d a t a c o n t a i n s
all
t(ie
data
from
the
recorded.
hours
>
in
which
"
fades
g reater
t h a n 10 6 6 w e r e
.In th is t h e s i s , such-an hour i s re fe rre d to .as a
•
‘
X
/
-
'
/- Vv
•
\
*
'
R e p r o d u c e d with p e r m i s s io n of t h e co p y rig h t o w n e r. F u r th e r r e p r o d u c tio n prohibited w ith o u t p e r m is s io n .
84
91F a d i n g
H our".
The r e s t o f t h e d a t a t h e n c o n s t i t u t e s
non-fading d a ta b ase.
.
B a s e d on t h e a b o v e c r i t e r i o n ,
am o u n t
of
fading
the
activ ity
a tim e c h a r 't showing t h e
f o r t h e t e n s e L e c t e d d a y s was
*
c o n s t r u c t e d and
featu re
th is
th at
s '
h a l f of Septem ber.
th e
is
four
is
fading
0\
in
F ig.
5.1.
Tne
m a in
was m o re p r o n o u n c e d i n t h e f i r s t
O n l y o n e f a d i n g h o u r was
consecutive
featu res are,
shown
days
observed
in ,
p r e s e n t e d f o r O c to b e r. . These
i n f a c t , v e r y r e p r e s e n t a t i v e ,, o f
the
actual
S itu atio n >
•In t h e t o t a l d a t a b a s e o f ,
fading
hours?
and
follow ing
sectio n s.
(0 dB)
hours,
there
are
P ropagation
conditions
associated
* ’
’
'T
f a d i n g >per£o'ds a r e
presented
in
non-fading
reference
239
It
i-s
noted
th a t ’ the
ta k e n a s t h e m edian
am plitude -o f
main r a y c a l c u l a t e d
from ' t h e n o n - f a d i n g
data base.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
w ith
the
am plitude
is
//
55
the
O
Qo
T
T
S e p t.6 /2 5 0
14 /2 5 8
259
260
19/263
264
O c t.2 1 /2 9 5
'
. 296
297
298
p — non-fading
—• fading hour
F ig.
5.1
Time a h a r t o f s e l e c t e d e x p e r i m e n t a l
o b s e r v a t i o n s f o r t h e 1980 e x p e r i m e n t .
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
5^ 3
P r o p a g a tio n D uring N o n -fad in g P e r io d s
* ’
Ray A m p l i t u d e s
^.-5*3.1
and D e l a y T i m e s
In th e te n days s e le c t e d
days
(259,
fading
263,.
(see
.co n d itio n s
Day 29 5 i s
F ig.
295,
To
illu strate
during
these
shown
in
F ig.
5.2
the
p eriods,
A t y p i c a l sweep f r e q u e n c y r e c o r d
• system ' is
experim ent,
2 9 6 ,j 2 9 1 , 298) c o n t a i n l i t t l e
5.1).
observed
x
used.
irj t h e 19 80
six
o r no
propagation
t h e d a t a f ro m
from - t h e
d iagnostic
to g e th e r w ith the ray p a th
«
p a r a m e t e r s . o b t a i n e d by t h e p a t t e r n s y n t h e s i s
m ethod .'
Two
»*
ray p ath s . a r e
id en tified .
The a m p l i t u d e and AOA o f t h e
*
, m a in
ray
are
0 . 4 dB
corresponding .v a lu e s
and
- 0 . 2 7 deg
respectively*.
f o r th e weaker ra y
ray)
a r e -11*.6 dB and - 0 . 4 8 d e g .
ray
is 2 . i 5 ns r e l a t i v e
(th e sea r e f le c te d
The d e l a y
to the d i r e c t
The
ray.
tim e
of
Except for
th is
the
/
am plitude of th e second ra y ,
the
value's
pred icted
in
the values f i t
S ection 4 .2 .
in
w e l l , w ith
The r e f l e c t e d
a m p l i t u d e o f - 1 1 . 6 dB, h o w e v e r , i s - c o n s i d e r a b l y h i g h e r
th e
predicted
value
of
ray
than
- 1 9 dB f o r a u n i f o r m g r a d i e n t o f
- 4 0 NU/km.
The v a r i o u s r a y p a t h c h a r a c t e r i s t i c s
p lo tted
in
may b e n o , t e d .
, w ith
a
F ig.
bn
Day 295
are
5 . 3 fro m w h i c h s e v e r a l p r o m i n e n t f e a t u r e s
F irst,
(
*
/
t h e main ray a m p l i t u d e i s v e r y s t a b l e
v a l u e o f 0 dB.
The second ra y a m p l i t u d e , h o w e v e r,
h a s . a v a l u e t h a t v a r i e s b e t w e e n - 1 0 and - 2 5 dB. T h e d e l a y
,
•
%
tim e o f
the
s e c o n d ' r a y r e l a t i v e , t o th e main ray i s a l s o
• •
<r
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
87
t
0
r
1
t
1
r
r
-
CD
)■'
-O
.*o
3
■M
"3.
E
< -20
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J
I
C7>
0>
3 180 a»
w
a
JC
Q.
*
90-
2
Of
cc
I
10.0
F re q u e n c y
Ampl.«{d8)
AOA (deg)
0.4
-0.27
-11.6
-0.48
10.5
(6Hz>
!*
Delay tns)
In
9.5
L
— reflected ray
r\.
F ig.
5.2
E x p e rim e n ta l (d o tte d ) and s y n th e s i z e d
d a - t a * r e c o r d a t 1 2 * 0 0 : 0 1 ADT.qn D a y '2 9 5 ,
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Reproduced
with permission
I ...>-----f-----1-----1-----1 ' ' I-----1-"’-l--- ►
"!“1 11 - ' ,
of the copyright owner.
H
1----- 1----- 1------1----- I------F-----F
1
I"" I• ■1-I
-H—I-----1-----1-----F
H
T-
1---------------1--------------- 1---------------1--------------- 1---------------r -
1-------1-------1------ H-------1-------1-------1-------1-------F
s .0
3
*
3 - 20
Further reproduction
1----- 1------F
CD
"O
0
3
-20
H
I - # ----- =1------ •— . I
I
I
-----1------1----- F
-F^-H ------ 1----- 4------1------1— ^F
prohibited without p e r m is s io n .
a»
s
0
Art
< -0 .4
^M a
<
N
o>
<u * 0
X)
r-0.2
<
5
-
0.4
I
1
I
t
_
F
.1
. 1
»
i ----------i
I
1
1
.
15
18 '
06
09
.
12
00
03
Day 295^ ■ ^
V dt
aT - relative d elay tim e
A1/A2 - m ain (1)/and second (2) fay am plitude.
AOAS / AOAl - e s tim a te s of m ain ray AOA from, slope (S) and 'in tercep t ( I ) . »
F ig.
5 .3
Ray p a t h c h a r a c t e r i s t i c s
1980 e x p e r i m e n t . '
o n a n o n - f a d i n g dajy, ( 2 9 5 )
1
_L
I
21
J
±
L
00
-
in
th e
00
00
s t a b l e w ith
I
These
a v a l u e o f b e tw een 2 and 3 n s .
*
ray p ath c h a r a c t e r i s t i c s o c c u r f r e q u e n tly
d u rin g
t
non-fading
p erio d s
and
alm ost
id en tical
behaviour
was
a
o b s e r v e d f o r Day 2 6 3 ,
*
The d i s t r i b u t i o n e
of
295,
296,
297,
298
(see
A ppendix 6 ) .
^
t h e m ain and s e c o n d r a y a m p l i t u d e s an d '
t h e d e l a y t i m e w e r e c o m p u t e d f o r t;he n o n - f a d i n g
d ata
base
\ .
and
t h e s e , a r e show n i n F i g s . 5 . 4 ( a ) t o ( c ) . T h e r a y p a t h
*
c h a r a c t e r i s t i c s o b s e r v e d o n Day 295 a r e w e l l i l l u s t r a t e d i n
y
th ese
d istrib u tio n
curves.
$
•
T h ^ m edian a m p litu d e s o f th e
*
m ain and seco n d r a y s
• .d irect
A
and
(in
reflected
th is
rays
d e l a y tim e a r e 0 dB, - 1 2 . 6
The
amount
ch aracteristics
of
is
*
the
i
d ire ct
and
case
th ese correspond
resp ectiv ely )
dB,
in d icated
in
by
ray
path
stan d a rd d e v ia tio n
d e v i a t i o n 'c o m p u ted f o r
ray am p litu d es
and th e r e l a t i v e
a
delay
tim e a re
1^3 ,dB>
2 .4 dB,
and
0 .3
ns
resp ectiv ely .
—
The l a r g e r ' s p r e a d
*
*
above
The
in
m
the
reflected
ex p erim en tal
ray am plitude
valu es
are
T a b le 5 .1 where t h e y a r e com pared w i t h
*
the
and t h e m e d ia n
th e
the
The s t a n d a r d
reflected
to
*
and 2 .3 n s r e s p e c t i v e l y .
v ariatio n
a b o u t t h e mean v a l u e s .
—
»
in S e c tio n
'
of
the
w ell
4 .2 .
d irect
w ith
reflected
th e
ray
It
is
seen th a t
is
noted.
sum m arized
in
the v a lu e s p r e d i c t e d
t h e m e a s u re d m edian v a l u e s
ray am plitude
and t h e delay* t i m e c o r r e s p o n d
»
, t
„
v alu es.
H owever,
the
m edian
pred icted
am plitude
of
-1 2 .6
dB
is
m o r e t h a n 6 dB
«
higher
t h a n t h e p r e d i c t e d v a l u e o f -1 9 dB.
!
To e x p l a i n
♦
th e
reflected
th is
l a r g e m easured v a l u e ,
i
ray am p litu d e
is c o n tro lle d
it
is
by t h r e e
*
l
*■
•
noted
#
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
th at
facto rs:
Reproduced
with permission
0.4-
of the copyright owner.
0 .2-
Further reproduction
0. 1*
0 . 1-
0
10
-10
-20
-30
Main ray amplitude (dB)
Ret. delay
(ns)
0.4-
prohibited without p e r m is s io n .
I
0 .1-
0
-10
-20
-30
Second ray amplitude (dB)
F ig .
5 .4
D i s t r i b u t i o n s o f th e ra y a m p litu d e s and r e l a t i v e
f o r t h e 1980 n o n - f a d i n g d a t a .
d e la y tim e
vO
O
T able 5 .1
E xperim ental and p re d ic te d
ray path c h a r a c te r is tic s
f o r t h e 1980 n o n - f a d i n g
' d ata
'
j
/
Ray P a t h
Param eter
P red ic te d
v e f lu e
✓
D i r e c t Ray
E xperim ental
m edian
stan d a rd
value
d ev iatio n
I
•
*
A m plitude,
o.or
dB
0.0
-
-0 .2 9
AOAf d e g
1 .3
'
- '
V
•
R e f l e c t e d Ray
A m plitude,
dB
AOA, d e g
D elay, ns
1
-1 9 .0
- 12.6
2 .4
-0 .5 3
-
-
2.5
2 .3
.
*
%
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
0.3
(a)
reflectio n
(c)
d iffractio n
am p^tude
lo ss,
(b)
lo ss.
In
d ivergence
estim atin g
the
lo ss,
and
reflected
ray
a p e r f e c t , s e a r e f l e c t i o n was a s s u m e d ,
reflectio n
loS s
is
zerop
The d i v e r g e n c e l o s s
i.e .
the
due t o
the
r-
cu rv atu re of
normal
the e a rth
conditions
and
process*.
*
1
how ever,
T h e m o re
is
the lo s s
te rra in .
In
th is
d iffractin g
a m o u n t s t o a p p r o x i m a t e l y 3 dB
is
included
in
the
under
ray tra c in g
sig n ific a n t
a nd
u n certain
com ponent,
v
/
d i f f r a c t i o n by t h e u n d e r l y i n g
due t o
c a s e ,- p o in t A (see F ig .
stru ctu re.
In
4.2) is
calcu latin g
the
the
main
d iffractio n
%
lo ss,
an a v e r a g e t r e e
h eight
te le p h o n e com panies f o r
of
(as
12^m
l
the p a th design)
used
by
the
was i n c l u d e d .
The
*
estim ated
h eight
lo ss
(the
i s .16 dB w h i c h i s
radius of
e n t i r e l y due to
the
t h e f i r s t F r e s n e l Zone a t A i s
tree
10 m ) .
*
T here is
than 4
i n f a c t no d i f f r a c t i o n
m
.
lo ss for
a tree
height le s s
'
An
a d d i t i o n a l p o i n t t o n o• t e i s t h a t t h e
path
p r o f i l e*
1
*
*
d a t a ^ was o b t a i n e d
from c o n t o u r
m aps
[36]
w ith h e ig h t
*
in terv a ls
actual
v
first
o
•
o f 1 5 . 2 4 m (50 f t ) .
The
h eig h t
of
Fresnel
illu stra te
the
zone
the
terrain
rad iu s.
im portance
d iffrac.tio n e f f e c ts
(in clu d in g
is
again o f 't h e
These
of
are dom inant.
immediate^- c o n c l u s i o n
terrain
is
u n certain tie s
order o f
co n sid eratio n s
the'
the
w ell
a c c u r a t e p a t h s u r v e y s when
In the p re se n t ca se ,
t h a t ■ the
trees)
in
♦
actual
h eight of
th e
the
at p o in t A is of th e-o rd er of 5 m
i
or . so
less
e stim atio n ,
•
than
the
v alu e used in the d i f f r a c t i o n
thus r e s u ltin g
i n t h e low
p red icted
#
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
logs
am plitude
*
*■*
93
f
of the r e f l e c t e d
5 .3 .2
ray.
M ain Ray A n g l e - o f - A r r i v a l
One p a r a m e t e r w h i c h h a s n o t b e e n c o n s i d e r e d So f a r
the
main
ray
AOA.
In S ectio n 4 .4 ,
p resence of a s h o rt delay
effect
of
causing
phase record,
is ' observed
ATouch
less
contam ination
due
The d i s t r i b u t i o n o f ' t h e
com puted . f o r
.summarized
of
the
noted t h a t th e
ray p a th has th e '
in th e s lo p e o f the
w h i c h would- o t h e r w i s e g i v e
The p h a s e r e c o r d i n t e r c e p t ,
i
is
t h a n 1 ns)
spurious v a r ia tio n s
S uch e r r o n e o u s b e h a v i o u r
295.
(le ss
it
t h e main ra y
AOA.
i n t h e r e s u l t s f o r Day
on t h e o t h e r
to
is
short
phase
h a n d , * shows
delay . p ath s
record
and
in tercep t
was
t h e r j o n - f a d i n g d a t a b a s e and t h e r e s u l t s
in F i g s .
5 . 5 ( a ) ’ and (b) .
in tercep t
value
versus
are
A lthough a c a l i b r a t i o n
the
a b s o l u t e AOA i s n o t
a v a i l a b l e d u e t o p r a c t i c a l d i f f i c u l t i e s ,* i t
is
known
in tercep t * is
lin early
related
.
(S ection 4 .4 ) .
AOA,
an
To r e l a t e
assum ption
•
grad ien t
of
thte m a i n r a y AOA *
in te r c e p t v a ly e to
B a s e d on t h i s
t h e AOA s c a l e and t h e c o r r e s p o n d i n g N - g r a d i e n t
approach
in
and t h e s e a r e show n i n F i g s . 5 . 3
in terp retin g
the
phase
is
a
assum ption,
were
and 5 . 5 .
T his
record
V
In tercep t re su lts
the
scale
*
co n stru cted
the a c tu a l
t h e e x p e c t e d d i r e c t r a y AOA f o r
- 4 0 NU/km.
v *
•
wa§ made t h a t t h e m e d i a n R v a l u e o f
in te r c e p t corresponds to
normal
the
to
t
N
th at
I
the
.
used fo r both ex p e rim e n ts.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
4
slo p e
and
Phase record intercept
0
a)
100
(deg)
200
300
0.3-
.=
0. 2-
-0.4
' _ Main ray
0
-
0.2
AOA
(deg)
-100
R efractivity gradient-
-200
(NU/km )
-5 0
1
5 10
50
90
P e rc e n ta g e of tim e AOA exceeded
F ig.
5.5
D i s t r i b u t i o n o f t h e m a i n r a y AOA f o r
t h e 19 80 n o n - f a d i n g d a t a .
%
•
♦
R e p r o d u c e d with p e r m i s s io n of t h e co p y rig h t o w n er. F u r th e r r e p r o d u c tio n prohibited w ith o u t p e r m is s io n .
gradient
-5 0
Refractivity
-1 0 0
(NU/km)'
-1 5 0
, ,
* t\
For
V . '-f
the
t h e 184 n o n - f a d i n g
resu lts
d irect
in
F ig.
hours m
5.5
show
r a y AOA^ i s , 0 . 3 2 d e g .
th.e
th at
19 8 0
data
£fche 9 9 . 8 . %
base.
range in
The c o r re s p o n d in g 9 9 .8
% range
f o r ' the r e f r a c t i v i t y g r a d i e n t i s
- 1 0 2 < d N / d h < 40 NU/km,
i
*
whi|ph i s e q u i v a l e n t t o 2 . 9 < K < 0 . 8 .
It
is
resu lts,
ray
is
also
the
notew orthy
99.8
%
range
1 . 0 < At < 4 . 2 n s
ex p erim en tally
same p e r i o d * i s
th at,
' based
on
the
above
in d e la y
tim e o f th e r e f l e c t e d
I
from r a y t r a c i n g ) . 1 The
(estim ated
o b se rv e d 99.8
% ran g e in d e la y
1 . 1 < At < 3 . 3 n s ,
tim e fo r
the
w h i c h -is i n f a j . r a g r e e m e n t _
m
w ith
the
range
estim ated
observations suggest
phase
record
I t also
non-fading
th e
as
hours,
tfce m e t h o d
AOA r e s u l t s .
These
in terp retin g
th e
*
'
i n t e r c e p t t o g i v e t h e m a i n r a y ^OA i s v a l i d .
serves
th at
from
evidence
th at,
th e atm osphere
of
at
least
du rin g
the
i s w e l l r e p r e s e n t e d by 3
v.
#
u n ifo rm N - g r a d i e n t m odel.
y ^
1
t
5 .3 .3
'
R efrac-tiv ity G radient V a ria tio n s
Some i n s i g h t on v a r i a t i o n s
in th e
o v erall
i n t h e Bay o f Furtdy may b e g a i n e d by a c l o s e
•thegray
path
relatio n
to
ch aracteristics
th is
p o in t,
it
given
is
in
am plitude,
the d i r e c t
The c o n v e r s e
and r e f l e c t e d
is a ls o
, -'O v e ra ll ' N -g ra d ie n t is
tru e .
In
4.6 t h a t
the r e f l e c t e d
a
ray
r a y AOA, find t h e d e l a y
F u rth erm o re, because
a f u n c tio n of th e bulk p r o p e r t i e s
1
*
the atm osphere, it^s value is not
* .4
A ppendix 6 .
1
■
’ tim e.
in
N -g rad ien t
exam ination of
n o te c f from F i g .
d e c r e a s e i n dN/dh w i l l c a u s e i n c r e a s e s
•
*
expected
to
' ’
R e p r o d u c e d with p e r m i s s io n of t h e co p y rig h t o w n e r. F u r th e r r e p r o d u c tio n prohibited w ith o u t p e r m is s io n .
change
the
in
too
E apidly,sa y ,
in
»
’
These f e a tu r e s
time f r a A e s
o f l e s s than a few h o u r s .
*o
%
may b e e t s e d * ag a m e a n s
of
id en tify in g
>.•
x
genuine v a r i a t i o n s
* <V
k9
in th e M -g rad ien t in th e atm osphere.
A good example o f
d u rin g
the p erio d
*■
41
these N -g rad ien t v a r i a tio n s occurred
f r o m L 6 : 0 0 ADT o n Day 259 t o 0 ^ . 0 0 ADT on
«
Day
260
(see
increases
ray,
and
F ig.
5 .6 ).
D uring t h i s
p e rio d g ra d u a l
i n t h e a m p l i t u d e anch df^lay t i m e o f . t h e r e f l e c t e d
t h e AOA o f the* d i r e c t r a y ,
were
observed.
appears
,to have
N -gradient
(more n e g a t i v e ) j | j h i c h p r e c e e d s t h e o n s e t o f more
rapid,
fading
a ctiv ities
,
Appendix 6 ) .
in th e l a t t e r
ray
■■ ?
*
path
param eters,
as a p p ro x im a te ly normal
o n 'D a y 295..
However,
a
more
- 4 0 NU/km
a t 0 8 : 0 0 ADT.
occurred
A lthough v a r i a t i o n s
were
not
(see
*
the
N -gradient
( - 4 0 NU/km)
negative
at
v alue
- 8 0 NU/km a p p e a r s t o h a v e b e e n r e s p o n s i b l e f o r
ch aracteristics
in th e
h a l f o f t h e day
**
,.
From t h e
estim ated
b e e n P a u s e d by a g r a d u a l i n c r e a s e
T h i'^
was
1 6 ; 0 0 ADT
of
about
the ray p a th
-The cha’n g e , i n N - g r a d i e n t
of
o v e r . a t i m e s p a n o f c l o s e t o 10 h o u r s .
i n tfhe
freq u en tly
N -gradient
observed
during
of
th is
the
m agnitude
experim ents,
p o s s i b l e l a r g e v a r i a t i o n s due t o s e a s o n a l c l i m a t i c
s h o u l d n o t be d i s r e g a r d e d .
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
changes
characteristic#
dile.to a
the* overall refractivlty gradient.
Variations .in ray'path
suspected variation in
5.6
18PJ ZdHV
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Fig.
(ap) tdwv
•' •
H ** The Sea Reflection
5.4
\
5 .4 .1
R eflectio n C o e ffic ie n t
In t h e r e s u l t s p r e s e n t e d so f a r ,
r
is
th e sea r e fle c te d
ray
S
•
observed
t o be r a t h e r p e r s i s t e n t i n
i t s p r e s e n c e a s an
im p o rta n t com ponent^of th e re c e iv e d s i g n a l .
T h e^p ro p erties
4
of
this, r e f l e c t e d
r£y a re d isc u s s e d
in t h i s
s e c t ’i o n . *
i
In
scatte red
surface)
C hapter
.
2,
it
was
noted
th at
'
.
the^
f
fie ld
.
resu ltan t
f r o m a r o u g h s u r f a c e ( i n t h i s c(a s $ t h e s e a
V
I
i s made up o f ' a s p e c u l a r r e f l e c t i o n a nd a d i f f u s e
scatte rin g
?
com ponent.
" f i r s t exam irted.
The s p e c u l a r
„
r e f l e c t i o n component i s
*
0
The r e f l e c t i o n phenomenon i s
q u a n t i f i e d by.
the R e fle c tio n C o e f f i c i e n t R ' such t h a t
s
R = p DR
s
Ks o
\
, i
v . c.
■
.
(5.1)
.
/
where
Ps
is
the s c a t t e r i n g
com ponent,,
reflectio n
D
grazing
of
d ivergence
a
smooth
sea.
arid
surface
of
the
t^e
is
the
(som etim es
m aterial
^
w here R + and
o
R Q, i s
called '
p ro p erties
a.
the
of the
-
*
; (5. 2)
c o s ^y )
s i n y ~ (Y2 — c o s 2y ) ^
s i n y + (Y2 - c o s 2y) ^
R “
o
to
emd' i s g i v e n by. [ 2 4 ]
. Y ^ s i n ^ + (Y
r " =
°
due
Xe f l ® c t i ° n
p aram eter
R + - Y ' s i n Y ~ (Y2 - c o s 2y )^2
and
specular
co efficien t
The
t h e a n g l e Of r e f l e c t i o n
angle)
reflectin g
the
for
f r o m ' a c u r v e d e a r t h , - and Rq
co efficien t
-function of
.is
co efficien t
'a re
the
■
reflectio n
(5 . 3 )
co efficien ts
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
for
v e rtic a l,
and h o r i z d n t a l p o l a r i z a t i o n s
•
is
of
*
the angle of . r e f l e c t i o n .
%
resp ectiv ely ,
Y
and
»
Y is
the no rm alized
ad m ittance
f
t h e medium g i v ^ n by
Y
where
.^
£ yr l
and
i
ui ’
‘
a r e , -the
‘
r e l ait itv .e * c o m p l e x' , >d i e l e c t r i c
*
c o n stan t
an d
the
(5 .4)
i-'
relativ e
m agnetic,
'
p e r m e a b ility o f the
m e d iu m .
The v a l u e o f R th e re fo ^ fe
is
c o m p l e x *• and
is
O.
9'
*- *
»- *» * * « .
* ^
'
»
fu n ctio n
of
t h e - i g a v e l e n g t h ’ a pd t h e ’ r e f l e c t i o n a n g l e
T h e m a g n i t u d e and" p h a s e . o f R i s shown _ i n
F ig . 5.7
as
* /
*
•k
fu n ctio n
o f ^and - y . On m d s t m i c r o w a v e ^ L O S , ' p a t h s (^the
p r e s e n t one included)^,
0 .5 deg
or
less,
y
As
for
*
D ivergence.
C o efficien t
D,
th is
"
of
the
earth curvature
and t h e
*
i s ■, a
9
l i n k g e o m e t r y , and
i s g i v e n by [ 2 4 ]
. ,
-h
2r i r 2
D -
a
«•
t
fu n ctio n
* y . '
u s u a l l y p i ^the,^ o r d e r
of
^
*
« •,
a,v alu e of
Rq ,=. - 1
fo r both
’
the
S
is^
th u s g iv in g
p o la riz a tio n s.
a
(5 .5)
1 +
a g . ( r j + r 2) . s i © y
where r
to
the
earth
th e
1
and r
*
2
end t e r m i n a l s o f
rad iu s.
ray
A ylesford
-
(5.5)
t h e p a t h , .and a
The d i v e r g e n c e l o s s
tracin g
refractiv ity
Eq.
a r e th e d i s t a n c e s from th e r e f l e c t i o n p o i n t
O tter
technique
Lake
co n d itio n s,
is 0 .6 9 .
in
th is
propag atio n
path
the
used
is
is the e f f e c tiv e
e *
ta k e n i n t o acco u n t in
work.
F osK tdie
under
normal
value of D c a lc u la te d 'u s in g
T his corresponds to a
divergence
o f a p p r o x i m a t e l y 3 dB.
/
)
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
loss
to o
1
Horizontal potarizalion
09
08
v
07
as
05
04
03
*
0
/
»
180»
150'
Vertical
'polarization
7 - - - reflection angle
F ig.
5.7
The m a g n i t u d e |R | a n d p h a s e <p o f t h e
r e f l e c t i o n c o e f f i c i e n t o f a v e r y smooth
sea.
e/e
= 8 0 , a = 4 mho/m.
[24].
. o
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
,5.4.2
The R e f l e c t i n g Area
Before d is c u s s in g
useful
to
gain
resp o n sib le
region
for
th at
an
the
For
'r e f le c tio n
of
is
of
0 . 2 5 deg
dim ensions of
is
the
the f i r s t F r e s n e l E l l i p s e .
The
is
reflectio n ..
given
normal
by
-
Eqs.
(2.22)
an d
A ylseford
path,
the
cond itions
O tter
Lake
F
where
X
Eq.
Y
denote
calcu late
(5 .1 ),
••
3 . 9 km /
” = 24.5 >
the
>
p arallel°
in le n g th .
—
co efficien t
the s c a t t e r i n g c o e f f i c i e n t
•
t h e a r e a b o u n d e d by t h e . f i r s t F r e s n e l E l l i p s e .
t
V
surface.
the rou g h n ess or
By a s s u m i n g a
height d is tr ib u tio n ,
model
Ps
using
Pg
for
is
a
•
.
ir r e g u la r ity of
G aussian
and
I t s h o u l d be n o t e d
a r e 2F,
a n d 2E,
IX.
1Y
the > r e f l e c t i o n
one r e q u i r e s
■ fu n ctio n of
5 - 6)
« ’7 »
dim ensions
E f f e c t s Of S e a S u r f a c e R o u g h n e s s
To
a r e g i v e n by
80x103
t h a t the axes of the e l l i p s e
5 .4 .3
len g th s
80x103
0 . 03x42x38xl06
1Y
and
, lo cated
and t h e r e f l e c t i o n
0.03x42x38x10 6
~
0.69
'
IX ~ s i n ( 0 . 2 5 )
p e rp e n d ic u la r to the path r e s p e c t i v e l y .
*
is
At; a f r e q u e n c y o f 10 GHz, t h e
and
/
T his
the sem i-axes o f the f i r s t F r e s n e l E l l i p s e
p
is
area
Lake
f ro m
c o e f f i c i e n t pg , i t
the
O tter
under
42 km
the
specular
ellip se
the
point
ap p ro x im ately ,
angle
idea
i s b o u n d e d by
dim ensions, of t h i s
(2 .2 3 ).
the s c a t t e r i n g
the r e f l e c t i n g
to r
the
Beckmann and S p i z z i c h i n o
[24]
\
/
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
surface
derived
.
th e value of
of
*102
pg as
p 2 = exp -(A<j>)2
O
where
'
'
.
(5.8)
p
re p re s e n ts the roo t-m ean -sq u are
(r.m .s.)
value
S
}
the s c a t te r i n g c o e f f i c i e n t .
T h e p a r a m e t e r A<j> ^ i s g i v e n
by
_ 4fT.A h.sin y
A<p =
where A h is
surface
the s ta n d a rd
irre g u la ritie s
T he v a r i a t i o n o f
in
d ecib els)
frequency
in terp reted
and i t
d eviation of
and
^rlP hnd
10 Glfz.
as
the
was s u g g e s t e d
y
is
y
M
the
h eight
reflectio n
the
angle.
co efficien t
(expressed
shown i n F i g .
sea
of
surface,
5.8 f o r
Ah'
a
is
s ta n d a rd d e v i a t i o n o f the-w ave h e ig h t
th at
[24]
(5 .1 0 )
)
t h e maximum o b s e r v e d wave h e i g h t .
on
ocean c u rre n ts
used
(5.9)
'
t,
The s e a s t a t e ,
dependent
is
F o r \ the
h M = 4 . 6 6 Ah
where h „ is
the
the s c a t te r i n g
versus
of
'
num erical
and
vario u s
th erefo re’
facto rs
and t h u s i s
th’e
wave
h e ig h t, . is
s u c h a s t h e w i n d s p e e d a nd
h ighly
s c a l e f o r m easuring
v ariab le.
A
sea s t a t e
is
commqnly
the W orld
«
M e t e o r o l o g i c a l O r g a n i z a t i o n C o d e 75 a n d t h i s
T a b le 5.2
[37] .
F u rth erm o re,
o c c u r r e n c e o f wave h e i g h t f o r
an e s t i m a t e o f
i^
shown
in
the p e rc e n ta g e
t h e o cean as a w hole i s g iv e n
in
T a b le 5.3
[37].
It
i s o b s e r v e d ^ t h a t t h e wave h e i g h t
•
!
e x c e e d e d f o r 50 % o f t h e t i m e i s
ap p ro x im ately
h ' = 1.4 m
M
Reproduced with permission o f the copyright owner. Further reproduction prohibited without permission.
/
103
S e a St ate
■V>
V
-10
- -
m
X)
c
\
32
o
S=
<K
oO
-
20-
-
C"
c
o
u
l/>
,-5 0 '--
.60- .5 0
.40
-60--
i h (m)
y . .. r e f l e c t i o n an g le (deg)
Ah...
F ig.
standard deviation o4 wave height
5 .8
The s c a t t ^ i n g c o e f f i c i e n t a s a f u n c t i o n o f
Ah f o r d i f f e r e n t v a l u e s o f y a t a f r e q u e n c y
o f 10 GHz. 4
\
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
T able 5 .2
W orld M e t e o r o l o g i c a l O r g a n i z a t i o n
1WM0) S e a - s t a t e S c a l e
[37]
S ea-state
number
WMO Cod e 75
D escription
w a v e h e i g h t (m)
-----------------------------------Calm
0
o - 0.1
Sm ooth
S lig h t
0 .1 - 0.5
0.5 - 1.2 *
M oderate
1 .2 - 2.4
Rough
2.4 - 4.0
Very ro u g h
High
4 .0 - 6.1
6 .1 - 9.1
Very h ig h ^
9 .1 -1 3 .7
>
P recip ito u s
Confused
o v e r 13.7
0
1
2
3
4
5
6
7
8
9
T a b l,e 5 . 3
P e r c e n t a g e o c c u r r e n c e o f wave h e i g h t s
f o r t h e o c e a n a s a w hole
[37]
Wave h e i g h t
(m)
f
f
0 - 0.9
0.9 - 1 .2
. 1.2 - 2.1
2 .1 - 3.7
3.7 - 6.1
Over 6 .1
Frequency o f
occurrence, %
20
25
20
15
10
10
------------------ *-------------------
]■
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
(e q u iv a le n t to
A h = 0.3 m ).
For r e f l e c t i o n a n g le s
*
under
normal
refractiv ity
of
betw een
co n d itio n s,
t h e m edian v a lu e o f th e s c a t t e r i n g
c o e f f i c i e n t in th e range
,
from
-2
to
- 8 dB .
m edian s c a t t e r i n g
(negated)
Si*nce
o <f* t h e r e f l e c t i o n
The e f f e c t o f a change
th is
case is
is
lo ss
for
also
for
a smooth s e a ,
the
m edian
seen to
v alue
th e sea r e f l e c t i o n .
in s e a s t a t e
Ah = 0 . 5 m.
in crease
*
on t h e
reflectio n
.The
to th e
range o f 4 to
angle.
reflected
due to a rough sea a p p e a r s t o
*
ray am p litu d e
am plitude
was d e p r e s s e d
accom panied
t ch aracteristics,
".caused
by
decreased
it
from i t s
a
-The
changes in
the
does
not appear
th at
effects.
16 dB
decreased
have
ray
n o r m a l v a l u e by m o re t h a n
by
atm ospheric
lo ss'
reflected
S ince th e d ecreased
am plitude
other
the
was
ray p ath
change
The e x p l a n a t i o n
a m p l i t u d e was c a u s e d by a r o u g h s e a
i
is
th at
was
the
supported
*i
by
an
for
the p a r t ic u la r
Lake
caseof
(see Appendix 6 ).
5 dB i n t h e a f t e r n o o n .
not
A
reflectio n
d e p e n d in g on t h e g r a z i n g
o c c u r r e d o n Day 297
thfe
by c o n s i d e r i n g 'a r o u g h s e a w i t h t h e
wave h e i g h t i n c r e a s e d t o
in
* * *
|R0 I= 1
co efficien t
l o s s may b e i l l u s t r a t e d
0.25
and
0 . 5 deg
•
«
F ig . 5.8 then g iv e s
entry
site ).
o f 22.5
sta tio n
o f "w indy"
d ay
in
the log -b o o k o f
(co n d itio n
In a d d itio n ,
observed
at
at
the 'O t t e r
a v e r a g e a n d maximum w i n d s p e e d s
km/h and 30 km/h w e r e r e c o r d e d
lo cated
the ex p erim en t
a t a nearby
S a in t John A ir p o rt,
m o n t h l y a v e r a q e w in d s p e e d o f 1 3 . 1
w eather
compared w ith
km/h.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
the
106
T h e e f f e c t ©f wave h e i g h t v a r i a t i o n s
on t h e
!
ray
am plitude
superim posed
u su ally
is
on ^ c h a n g e s
reflected
not o b serv ed in
iso latio n
due
causes
such
as
change
in
the
to
N -gradient
v aria^ id n s.
refractiv ity
g ra d ie n t w ill cause
o th er
For- e x a m p l e ,
a
v ariatio n s
in
but is
the
path
t
clearance
of
reflectio n
the r e f l e c t e d
angle
and
in d iv id u al e ffe c ts
5 .4 .4
ray,
thus
as, w e l i , a s a c h a n g e i n ^ t h e
the
reflectio n
lo ss.
th e re fo re are not observed
in
The
iso latio n .
D i f f u s e S c a t t e r i n g Component
Thus f a r ,
th e e m p h a s is h a s been p l a c e d on t h e s p e c u l a r
reflectio n
com ponent.
It
appearsth a t
behaviour o f
the r e f l e c t e d
ray
is q u ite w ell accounted
by
th e s p e c u l a r component a lo n e .
d iffu se
scatte rin g
It
is
the observed
for
noted, t h a t f o r
the
c o m p o n e n t , we h a v e
r
■
R j = PjR'
d
d o
'
(-5.1$
4
where
R
d
scatte rin g
the
n
are the r e f l e c t i o n c o e f f i c i e n t
a nd
d
c o e f f i c i e n t f o r t h e d i f f u s e c d m p o n e n t , and Rc i s
r e f l e c t i o n c o e f f i c i e n t o f a smooth s u r f a c e .
of
[24].
the
and
was s u g g e s t e d t o
lie
w ithin
When o b s e r v e d a t a s i n g l e
diffu se
the r e f l e c t e d
am plitudes
e f f e c t of
frequency,
to produce ra p id
ray.
the
are
obtain ed
from
th e d i f f u s e component
value
th e range o f 0 to 0.35
component i s
S ince
The
d irect
sweep
and
the
effect
flu c tu a tio n s
reflected
frequency d a ta ,
(w h ich h a s random p h a s e )
of
in
ray
the
is
e x p e c t e d toj-be a v e r a g e d o u t w i t h i n a sweep and c o n s e q u e n t l y
\
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
1 07
*
is
not expected to
a f f e c t the e stim a te d ray am p litu d es.
■
a
\
5.5
'
P r o p a g a tio n D uring Fading P e r io d s
5 .5 .1
/ ,
R e s u l t s on Day„ 250
Most o f
occurred
resu lts
the fad in g
on
"
a c tiv ities
Days 2 5 0 ,
258,
in th e te n s e l e c t e d days
and 259
(see F ig .
f ro m Day s 250 and 258 a r e u s e d
m echanisms
resp o n sib le
to
5 .1 ).
The
illu strate
the
%
f o r f a d i n g on t h e A y i e s f o r d - O t t e r
Lake p a t h .
*
Th e r a y p a t h c h a r a c t e r i s t i c s f o r Day 250
in
F ig.
5.9 .
D uring th e f i r s t
tim e d e c r e a s e s s l o w l y from
noon.
The
decrease.
reflected
The
h a lf of
3 .5 ns t o
ray
d i r e c t ray
th e m ild f a d i n g
less
is
the delay
than
2 ns
at
a m p l i t u d e a l s o sh ow s a
sim ilar
does
sim ilar
not
i n d i v i d u a l sweep
ex h ib it
a
is observed.
records
and weak r a y p a t h .
reveals
An
th at
The s h o r t d e la y
*
su sp ected to
U n fo rtu n ately ,
plo tted
was c a u s e d by t h e p r e s e n c e o% a s h o r t ‘d e l a y
( l e s s th a n 0 .5 ns)
path
are
the day,
d e c r e a s e b u t m i l d f a d i n g o f a few d e c i b e l s
exam in atio n of the
V
be
as d escrib ed
in
of
atm ospheric
C hapter 4,
the
ray
o rig in .
ray
path
c h a r a c t e r i s t i c s of such s h o rt delay rays are o u ts id e o f the
r a n g e s r e s o l v a b l e by t h e e x p e r i m e n t a l e q u i p m e n t
fin ite
frequency
s w eep
range.
confirm ed
by e x a m i n i n g t h e
in tercep t
of
the
phase
to
a
I t s p r e s e n c e , ho wever-,
is
behaviour
record.
of
Once
'th e
again,
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
due
slo p e
and
spurious
Reproduced
with permission
T
of the copyright owner.
CD
I *"*
I
‘
I '
1 -------- 1-------- 1--------1-------- 1-------- r
I
Further reproduction
-3
E
H
1---- 1-----h
H
1-----1-
H
I
1-----1
1-
iwi
0
x>
^ -20
H
1-----1---- h
H
prohibited without p e r m is s io n .
-I
f-
I
■
H
1---- 1-----F
CD
2
2 -20
cn
<u n S-; -lr
2
0
in
*
<-0.4
<
- * t- “
. iU
*i 1-*: ••*
,•
{<♦>*:• Ja
| * . 1 i. ■
' u;-‘itijLk*‘ i '±h•'’ ••*u#Bui4 » 'T u W < ( n r ^ itL dii'Ml ? . r
i& li
4*4
I
1____ 1 • 1 >.
• >
'
•
00
03
Day 250
& T-relative delay time.
A1>£A2 - main(1) and second (2) ray amplitude.
A0AS / AOAl - e s tim a te s of main ray AOA from slope (S) and intercept (I).
Fig.
5.9
Ray path characteristics on' a fading day
experiment.
(250)
in the 1980
o
00
v a r i a t i o n s , in th e phase re c o rd s lo p e
n o t c a u s e d by g e n u i n e v a r i a t i o n s
A p a r t from th e s h o r t d e l a y
am plitude
a*nd d e l a y t i m e o f
1 2 : 0 0 ADT
( m ore
suggests
n eg ativ e).
an
at
o b s e rv e d w hich
in th e
rays,
increasing-
the decrease
in
the f a s t
and
the
ra y from 00:00 t o
refractiv ity
1 4 : 0 0 ADT
was
m a i n r a y £ 0 A.
the r e f l e c t e d
T his p receeded
f a d i n g which s t a r t e d
is
g rad ien t
and s u b s t a n t i a l
continued
through
m idnight.
T w o. d i f f e r e n t
If
observed
during
f r o m '1 4 :0 0 to
types
of
fading
i
th e above p e r i o d .
1 7 : 0 0 ADT.
behaviour
The f i r s t
The r e f l e c t e d
may*
be
type o c c u rre d
am plitude
and
” .delay
tim e
a r e n o t much d i f f e r e n t f r o m t h e n o r m a l v a l u e s .
*
*
H owever, t h e main ra y
p a th - shows
rap id
and
su b stan tial
fading
and
enhancem ent..
presence of a larg e
path .
T his
freq u en tly
of
are
attrib u ted
am plitude S h o rt d elay
o b serv atio n
observed
d iscu ssio n s
These
in
is
not-
the
19 8 1
th ese atm ospheric
to
atm ospheric
unique
and
was
experim ent.
ray p a th s
C hapter 6 s in c e they are b e t t e r
illu strated
'
%
re su lts.
For th e p r e s e n t , i t is n oted t h a t
the
ray
m ore
D etailed
are delayed to
by
the
1981
the a d d i t i o n a l
i
r a y p a t h was c a u s e d by t h e p r e s e n c e o f a n a t m o s p h e r i c l a y e r
*
occurring,
at
a
height- su ch t h a t b o t h
the la y e r .
. \
A d i f f e r e n t type1 o f
op erativ e
from
amount o f f a d i n g o f t h e
to
m echanism
m idnight
d irect
ray
%
i
.
fading
1 7 : 0 0 ADT
antennas a re w ith in
compared w ith th e p r e c e e d i n g p e r i o d .
is
on
seems
to
Day 2 5 0 .
slig h tly
At the
be
The
reduced
*
same t i m e , t h e
*
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
*
reflected
ray
sho ws an
10 dB and a t t i m e s
increase
in
am plitude
even e x c e e d s the' d i r e c t
f
1
of
ray in a m p litu d e
„
t o beco me t h e m a i n r a y p a t h .
T his l a t t e r
b eh av ib u ris
*
illu strated -,
by
the
AOA
r e c o rd , i n t e r c e p t from
1
from
record
C hapter 3
v alue
&k i n d i c a t e d
2 0 : 0 0 ADT
to
by t h e a n a l y s i s
ro u tin e
observes
m a i n *AOA. i n d i c a t e s
two
*
th at
tha.t
during
d istin ct
b y .th e phase
m id n ig h t'.
is
w ell
at
and 4 t h a t t h e AOA o b t a i n e d
• * (main) , r a y , ' one
nearly
R ecallin g
from t h e p h a s e
of
the
stro n g er
th e tim e p e r i o d
v alues.
The
the
values
of
t h e AOA-of t h e d i r e c t
*
and
K
‘- - 0 .1 7
and - 0 . 4 deg c o r r e s p o n d t o
♦»
the re fle c te d rays re s p e c tiv e ly .
f
Irt a d d i t i o n
a
2.5
sig n ifican t
to
the am p litu d e
and g r a d u a l
and AOA
increase
in
c h a ra c te ristic s,
th e d e la y ' tim e
t o 5 n s i s o b s e r v e d b e t w e e n 1 6 : 0 0 and- 1 8 : 0 0 ADT,
w hich t h e d e l a y tim e
is
stab le
from
after
a t ap p ro x im ately 5 n s.
* # *
Several
d etail
sweep
frequency
and two r e p r e s e n t a t i v e
records
were
exam ined k i n
o n e s a r e shown i n F i g s .
5.10
and 5 . 1 1 t o g e t h e r w i t h t h e r a y p a t h . p a r a m e t e r s o b t a i n e d
p attern "
sy n th esis.
The
record
18: 0 4 : 5 6 ADT s how s
th a t 'th e
'
*
am plitude
of
- 5 dB b u t
an
-0,.23 d e g .
For th e r e f l e c t e d
am plitude
and
d elay
tim e
shown
d irect
in
F i g . -5.10 f o r
has
a reduced
»
a p p r o x i m a t e l y n o r m a l AOA* o f
ray,
are
ray
in creases
observed.
in
both
More
the
extrem e
*
*
i s shown i n F i g . - 5 . 1 1
for
2 1 : 0 0 : 0 6 ADT when a
/ .
\
'
r e f l e c t e d ' ray
a m p l i t u d e i s a c c o m p a n i e d by e l e v a t e d
behaviour
large
by
AOA V a l u e s and a d e l a y t i m e o f 4 . 7 i t s /
* ‘t
•
R e p r o d u c e d with p e r m i s s io n of t h e co p y rig h t o w n e r. F u r th e r r e p r o d u c tio n prohibited w ith o u t p e r m is s io n .
’
4
^
i Ti
CL
E
< -20
••
X>
••
180
10.0
9.5
Frequency
Arrvpl.(dB)
F ig.
AQ# (deg).
10.5
(GH z)
Delay ( n s )
-5.1
-0.23
-
-9.0
-0.52
3.3
5.10.
"
— reflected
4
ray
E x p e rim e n ta l ( d o tte d ) and, s y n t h e s i z e d
d a t a r e c o r d a t 1 8 : 0 4 : 5 6 ADT o n Day 250,
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
TD
O.
-20
a
10.5
9.5
Frequency
A m p l . (dB)
AOA ( d e g )
.
(GHz)
Delay (n s)
-0.17
0.1____________ - 0 / 1 ____________ 4.7
— r e f l e c t e d ray
x amplitude, of direct ray c h a n g i n g during s w e e p .
'
%
. F i^.
5.11
E x p e rim e n ta l ( d o tte d ) and s y n th e s i z e d
d a t a r e c o r d - a t 2 1 : 0 0 : 0 6 ADT on Day 2 5 0 .
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
1 13
These ray p a th c h a r a c t e r i s t i c s r e
atm ospheric
illu stra te
layer
the p o in t,
A n - - 1 5 NU,
below
the
Ah = 100 m,
and
effect
t h e main r a y
the
layer
on
(radio-hole e ffe c t)
and t o
in
F ig.
The r a y
5.12.
The
is to decrease
raise
To
param eters
’h Q = 150 m i s u s e d .
a r e shown
of
w i t h an
an ten n as..
an a t m o s p h e r i c l a y e r w i t h
p a t h s u n d er such c o n d i t i o n s
am plitude
\
occurring
co n sisten t
t h e A<5a.
the
As f o r
the
reflected
ray , th e in c r e a s e in am p litu d e is e x p la in e d
1
by t h e i n c r e a s e d c l e a r a n c e a t * t h e
d iffractio n
poin t
(by
approxim ately
is
4m
or O . S F j ) .
F u rth erm o re,
in c r e a s e d s u b s t a n t i a l l y due to
index
below
the
layer..
an
enhanced
These r e s u l t s
T ab le 5 .4 .
,
before
b oundaries,
appears
th at
in terv en in g
illu strated
reflected
is
noted t h a t
1 7 : 0 0 ADT a r e
ob tained
the
lay er
p erio d .
those
after
descended
in
ray
w ith in
the
1 9 : 0 0 ADT
It
are
th erefo re
h e ig h t during
The e x p l a n a t i o n a p p e a r s to be v a l i d
by t h e g r a d u a l i n c r e a s e i n
th e .delay tim e ,
£ he
m eteo ro lo g ical
S a in t • John
lo cated
site .
The
the
as
the
and t h e d i r e c t r a y AOA.
evidence su p p o rtin g the p re se n c e o f a la y e r
from
MSL)
the
a s s o c ia te d w ith a
a l a y e r below th e a n t e n n a s .
w eather s t a t i o n a t
antenna
w hile
ray am p litu d e,
F u rth er
above
it
a h e i g h t such t h a t b o th a n te n n a s a r e
a s s o c ia te d w ith
V
a r e summ arized in
*
path, c h a r a c t e r i s t i c s
layer
refractiv e
'
From t h e a b o v e d i s c u s s i o n s ,
layer at
th e d e la y tim e
10 km
h o u rly
data
A irport
south-w est
tem perature
rec'o rd ed
(elev atio n
of
is
a t the
109 m
t h e O t t e r Lake
and
wind
V
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
speed
Reproduced
with permission
of the copyright owner.
. O t t e r Lake
Aylesford
400
*r
Further reproduction
.£3
e 200
prohibited without p e r m is s io n .
g>
a*
x 100
M, 10 NU/div.
D istan ce
Note.
1) B a s i c
N-profile:
2) A t m o sp h e ri c layer:
Fig. 5.12
No = 3 4 0 NU,
aN
= -15NU,
(km)
dN /dh=:-40NU /km
Ah=l00m,
h„=150m
Propagation on the Aylesford - Otter Lake path when an atmospheric
layer is present below the antennas..
_
A 15
T able 5.4
■*
Comparison o f e x p e r i m e n t a l r e s u l t s
and r^y p a t h p a r a m e t e r s e s t i m a t e d
. ^with r a y t r a c i n g f o r a l a y e r p r e s e n t
below t h e a n t e n n a s
Ray P a t h
Param eter
E xperim ental
Day 250
1 8 : 0 4 : 5 6 ADT 21 : 0 0 : 0 6 ADT
D irect ray
A m p l i t u d e , dB
AOA, d e g
R e fle c te d ray
A m p l i t u d e , dB
AOA, d e g
Rel. d e la y , ns
Note:
1)
Mfc. A
'
-5 .1
-0 .2 3
-4. 7
-0 .1 7
-2 .7 -0.26
-9 .0
-0 .5 2
• 3.3
■
0.1
- 0.41
A .7
-4 .0
-0 .4 0
4.8
AOA*s a t O t t e r La ke
,
t
2)
3)
*, •
Ray T r a c i n g
w ith duct
r e f l e c t e d ray am plitudes are e stim a te d
. assu m in g t h a t t h e e x p e r i m e n t a l median
a m p l i t u d e o f - 1 2 . 6 dB i s t h e v a l u e f o r
4/3 - e a r t h .
d u c t, p a r a m e t e r s :
AN = - 1 5 NU
Ah = 1 0 0 ' m
h Q = 150 m
? ‘
At
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
t h r o u g h t h e d a y a r e shown i n F i g .
fading
at
1 4 : 0 0 ADT
tem perature
is
5 .1 3 .
m arked
1 9 : 0 0 ADT
by
in t h e a f t e r n o o n , w hich
d e c re a se o f alm o st 7° G in 6 h o u rs
also
co rrelated
The o n s e t o f r a p i d
«the
is
.
in crease
in
f o l l o w e d by a r a p i d
The s t a b l e
la y e r s at
w e l l w i t h t h e wind s p e e d w hich
d e c r i f e s e d g r a d u a l l y t o caj.m c o n d i t i o n s a t 2 1 : 0 0 ADT.
Both
*■ ••
*
these
conditions
are
f a v, o u r a b l e
to
the fo rm atio n of
t
atm ospheric la y e r s .
At t h i s
an
point i t
atm ospheric
is
layer
im p o rta n t to n o te t h a t
which i s h o r i z o n t a l l y
a model
uniform , w ith
,
w ell defin ed
is
at
u atio n .
a
sim p lified
Howevfer, i t
does a llo w the g ro s s
ray p ath s
*
i
b o u n d a r i e s a n d w e l l t^eh av ed v a l u e s
best
t o be,
of
is
p ictu re
seen t h a t
of
the
dN /dh,
real
sit­
t h e use o f such a
m o d e l1
an d .im p o rtan t f e a tu r e s of
explained.
of
Tem poral
the re c e iv e d
v ariatio n s
of
the
actu al
ray
path
param eters
are
read ily
i n t r o d u c e d by
‘
lo calized
turbu len t
air
m a s s e s .^ D escrip tio n ^
of
such
*
’stru ctu res
i n t h e f o r m o f t h e r m a l p l u m e s may b e
9
in M c A llis te r* e t a l .
[38] . T h e s e t h e r m a l p l u m e s a r e
tu rb u len t
i
-
found
reported
.to
h a v e h o r i z o n t a l d i m e n s i o n s t h a t r a n g e f r o m 70
t o 840 m.
The
occurrence
' therefore
can
have
ch a ra c te ristic s,
such
sig n ifican t
recallin g
th at
th e
tu rb u len t
effects
rad ius
stru ctu res
on t h e r a y p a t h
of
the
L
•
F r e s n e l z o n e a t raid p a t h
*
of
is of
first
■»
t h e o r d e r o f o f i l y 25 m.
S
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
t
• I
1 17
CJ>
£ 10
7*.
i,
\
X>
06
Day. 250
F ig.' 5 .1 3
12 .
18
ADT
T e m p e ra tu re and w ind s p e e d o b s e rv e d a t
S a i n t J o h n A i r p o r t o n Day 2 5 0 .
o
%•
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
00
5 .5 .2
R e s u l t s ' o n Day 258
•Bhe f a d i n g o b s e r v e d o n Day 258 i s
also
of
in terest.
The
r a y p a t h c h a r a c t e r i s t i c s on t h i s d a y a r e s u m m a r i z e d i n
. «
F ig . 5.14.
The c o r re s p o n d in g m e t e o r o l o g i c a l d a t a is
shown
In
F ig.
5.15
for
the
period
f r o m m i d - d a y On Day 257 t o
»
In a d d i t i o n , i t i s noted t h a t a t o t a l
m i d - d a y on Day 2 5 8 .
of
3 6 . 6 mm
of
rain
A irp o rt sta rtin g
the
good
a t 0 7 : 1 0 ADT.
co rrelatio n
m eteo ro lo g ica l.d ata
from
was r e c o r d e d o n D ay 258 a t S a i n t J o h n
m idnight
is
to
of
In stu d y in g
the p ro p a g a tio n
noted.
F irst,
0 7 : 0 0 ADT
on
these
resu lts
r e s u lts w ith^the
heavy fa d in g o c c u r re d
D a y , 258 .
The
fad in g
•i
ch a ra c te ristic s
and
are
are s i m i l a r
thus e x p la in e d
to th o se
observed
on
Day 250
by t h e p r e s e n c e o f a l a y e r . . . Aga-in
t h e win<T c o n d i t i o n w as r e p o r t e d
to
be calm .
The; r a p i d
' ■
*
fading
stopped
a t 0 7 : 0 0 ADT w i t h t h e t e m p e r a t u r e i n c r e a s e
at
sunrise
and.w hen t h e wind s t a r t e d
to develop.
A d i f f e r e n t , t y p e o f f a d i n g was o b s e r v e d f o r
of the day.
reflected
the
rest *
The s i m u l t a n e o u s f a d i n g o f b o th ||^e d i r e c t
rays
c a u s e d by r a i n
(of; up t o 10 dB b e l o w t h e
atten u atio n .
normal v a lu e s )
«
5.6
was
\
«
»
and
•
I
Ray Path S t a t i s t i c s
»
•
*
*
r
✓
'
«q
*
U sing a s d a t a b a s e t h e d a t a
*
*
the d i s t r i b u t i o n s of
th e d elay
*
f r o m t h e 55 f a d i n g
9
•
hours,
a
t h e m ain and s e c o n d r a y a m p l i t u d e s
tim e were c o m p u te d .
The r e s u l t s
are p re s e n te d
o
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
a nd
in
Reproduced
with permission
of the copyright owner.
ijt'iiitjiuHjm**1n1r
Further reproduction
4
......
ocn>
prohibited without p e r m is s io n .
S
0
in
3 - o .a -
:>5'
-
0.2
00
03
Day 258
aT
06
12
15
10
21
00
ADT
- relative d e l a y time.
A1/A2 - main(1) and second (2) ray amplitude.
AOAS / AOAI - estim ates of main ray AOA from slope (S) and intercept (I).
Fig.
5.14
Ray path characteristics* on a fading day
experiment.
(258) in the 1980
\0
120
Q.
|
20
x>
12
Day 257
F ig.
5.15
18
00
06
Day 2^8
ADT
T e m p e ratu re and w ind s p e e d o b s e rv e d a t
S a i n t J o h n A i r p o r t o n f ra ys 257 a n d 2 5 8 .
f '
i'
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
12
F i g s . 5.16-<a). t o
It
is
first
am plitude
noted
th at
the
dB,
p erio d s.
These
m o d e l - t h a t t h e h e a v y f a d i n g on
atm ospheric
to
lay ers
the
the
fit
lin k
was
th is
effects
reflected
ray
of
in crease
the r e l a t i v e
ray
in w ith the
caused
are:
to
by i n c r e a s i n g
the
lo ss,
delay of th e
compared
by
for
p lo ttin g
Normal P r o b a b i l i t y c o o r d i n a t e s .
to
(b)
the d iv e rg e n c e
The r a y p a t h c h a r a c t e r i s t i c s
by
(a)
d efo cu ssin g ,
reflected
♦
in d e x below t h e l a y e r .
an e n h a n c e d r e f r a c t i v e
are
w hich
am plitude
c l e a r a n c e a nd r e d u c i n g
periods
second
resu lts
t h e d i r e c t r a y a m p l i t u d e by
increase
terrain
and
c o m p a r e d w i t h t h e v a l u e s o f 0 dB ahld - 1 2 . 6 , dB
non-fading
decrease
main
d u r i n g f a d i n g h o u r s h a s m e d i a n v a l u e s o f - 3 . 1 dB
and - 1 0 . 2
during
(c) .
non-fading
th e
and
( c)
r a y due t o
and f a d i n g
d istrib u tio n s
T his p r e s e n ta tio n a ls o
on ’
has
*
the
effect
of
^ d istrib u tio n s.
F ig.
5.17.
d elay
em phasising
the
*The d e l a y t i m e
The
tim e
ta il
ends
d istrib u tio n
is
of
shown
the
in
higher p r o b a b ility o f o ccu rren ce of la rg e
values
during
fading
is
p a rtic u la rly
sig n ific a n t.
The
ray
non-fading
and
(b).
path
a nd
fad ing
A lso p l o t t e d
d istrib u tio n
of
am plitude
the
d istrib u tio n s
d a ta a re com pared in F i g s .
in F i g .
5.18(a)
resu ltan t
is
am plitude
v ector p lu s a R a y le ig h -d istrib u te d vector
power
of
for
the
of
[39] ,
co n stan t
vecto r.
The
main
ray
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
5.18(a)
th eo retic al
a co n stan t
the
t h e R a y l e i g h v e c t p r b e i n g - 1 4 dB r e l a t i v e
power in th e
the
mean
to the
am plituc^
(c)
fa)
0.2-
c
o
o 0.1-
o
a
k.
U-
u.
10
0
-10
-20
-30
Main ray am plitude (dB)
2
U
6
B
10
12
Rel. delay (ns)
0 . 2-
c 0.1-
(/)
in
-30
0
-10 •
-20
Second ra y amplitude (dB)
F ig.
5.16
D i s t r i b u t i o n s o f th e ra y a m p litu d e s and r e l a t i v e
t"he 1 9 8 0 f a d i n g d a t a .
*
d e la y tim e f o r
rv)
r\)
1980
U)
c
to
fading
a*
'O
>
4»
o:
0.01
P ercen tag e o f tim e
F ig.
41
5.17
at
exceeded
D is tr ib u tio n s o f the r e l a t i v e d elay
t i m e ( s e c o n d r a y r e l a t i v e t<? t h e ,
m a i n r a y ) f o r t h e 1980 n o n - f a d i n g
a n d f a d i n g d a t a p l o t t e d on Normal
P ro b a b ility paper.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
1 24
Q
%
Constant plus Raleigh
fading
0.01
0.1
5
50
10
90
99
fading
E -1 0 n an -fad in g
3 -2 0 -
o.ov d.i
1
5
P e rc e n ta g e
F ig,
*
| «
5.18
50
10
of tim e a m p litu d e
90
99
9 9 .9
99 .9 9
exceeded
D is tr ib u tio n s o f ray am plitudes fo r
t h e 1980 n o n - f a d i n g a n d f a d i n g d a t a
p l o t t e d on Normal P r o b a b i l i t y p a p e r .
\
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
■
125
d istrib u tio n
th a t
of
for
th e
suggests
the n o n -fad in g
C onstant ‘ P lus
th at
the
a m p litu d e '/^ d u rin g
m u ltip ath
of
m ild
th e type d isc u s s e d
v a ria tio n s
fading
in
in S e c tio n
p erio d s,
in
periods
occu rrin g
D ifferen t s ta t i s t i c s
during
clo se ly
approxim ates
R ayleigh d i s t r i b u t i o n .
n on-fading
in terferen ce
data
the
are
T his
d irect
due
to
a tu rb u len t
ray
random
atm osphere
2 .4 .3 .
are observed
for
the
w ith e n h a n c e m e n t o f up
t o 9 dB a n d
f a d e s o f - 1 5 dB.
These s t a t i s t i c s
the
fading
c a u s e d by l a r g e a m p l i t u d e b u t s h o r t d e l a y
rays
(
was
less
at
am plitude
is
in terferin g
least
than
in
1 ns).
fact
w ith th e
part
of
stro n g ly
In t h e s e c a s e s ,
the
resu ltan t
au x iliary
the
suggest
, m ain ra y
fading
of
ray(s).
th at
the
m ain ray
th e
d i r e c t ray
F urth erm ore,
at
was c a u s e d by t h e d e f o c u s s ^ i n g
#
e f f e c t due t o a l a y e r o c c u r r i n g b e lo w t h e a n t e n n a s .
It
also
d u rin g
n o te d t h a t t h e m ain ray a m p l i t u d e d i s t r i b u t i o n
*V •
f
fading
99 %
.
i s ap p ro x im ately
lim its.
fading
value,
data
log-norm al w ith in
The m e d ia n a m p l i t u d e o f
t h e m edian a m p litu d e o f
th e ,1 %
and
th e'
t h e m ain ra y f o r
i s d e c r e a s e d by 3 dB r e l a t i v e
w hile
is
the
to th e no n-fading
tne r e f le c te d
ray
is
........
t
i n c r e a s e d by 2 . 4 d B - d u r i n g f a d i n g .
The s t a t i s t i c s
non-fading
data
d istrib u tio n .*
d istrib u tio n
if
a p o sitiv e
«
it
can
be
of th e
fo llo w s
The
is
reflected
c lo se ly
th eo retic al
not
clear.
ray am p litu d e fo r
th at
b asis
tn e
of
a
log-norm al
for
a
log-norm al
I t has been s ta te d
th at
" ...
p h y s ic a l m agnitude X obeys a lo g -n o rm al
law ,
’
in terp reted
as
being
the product of a g re a t
f*
/
-
*
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
I
number o f
^
[41]
independent v a r ia b le s "
the
log-norm al
■
[40] .
d istrib u tio n
process.
In
v ariatio n
of
d iffractio n
(c)
v ariatio n s,
'
v ariatio n
in
in
reso lu tio n
»
(a),
noted t h a t th e
ray i s
in
(b)
and
atm ospheric
roughness
lo ss.
[37],
A
is m anifested
(d)
due
W hether
to
a
an
th e lo g -n o rm al behaviour of
the
However,
it
is
in terestin g
a lo g -n o rm al am plitude d i s t r i b u t i o n
radars
(a)
s\ch
not c e r t a i n .
sea-clu tter'
a
.
exam ple,
angle.
fact
, include:*
d ivergence
(c),
reflectio n
is
is
thus s u rf a c e
for
can a c c o u n t f a r
to note 't h a t
a nd
'
th e v a lu e o f dN /dh,
ray
observed
h eig h t
changes in
m u ltip lica tiv e
te rrain ,
in
the
it
a
these
v a ria tio n s
in
reflected
in terv e n in g
(d)
in c o rre sp o n d in g
ex p lan atio n
co n tex t,
facto rs,
wave
and
by
the r e f l e c te d
several
by t h e
tu rb u len ce,
change
present
in a m p litu d e o f
fu n ctio n
\
the
I n Meye.r a n d M ayer
*
s a i d t o a r i s e from a
is
t h e o r y o f e l e m e n t a r y e r r o r s com bined
<26
(or
sea-echo)
w as
retu rn s
also”
in high
[42].
*
\
•
*
t
*
*
•'
5.7 Summary
D uring
ch a ra c te ristic s
non-fading
in d icate
. m odelled w ith a uniform
the
sea
‘reflectio n
p erio d s,
th at
present
m e d i a n a m p l i t u d e ^ f - 1 2 . 6 - dB a n d a
2.3
ns,
sig n ifican t
fading
ray
p ath
."the a t m o s p h e r e may b e w e l l
refractiv ity
is
the
g ra d ie n t.-
most
of
m edian
a c tiv ities,
A lth o u g h
th e tim e w ith a
delay
tim e,
were n o t o b s e r v e d
i
*'
‘,
4
of
»
*
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
4
v
127
^
during
t h e month o f ' O c t o b e r i n ' 1 9 8 0 .
From a c o n s i d e r a t i o n o f
range
the d i r e c t
o f thie r e f r a c t i v i t y g r a d i e n t f o r
was f o u n d , b e
-102
< ^ N / d h < 40 NU/km.
i n t h e d i r e c t r a y AOA i s
The s e a r e f l e c t i o n
found
th at
except
re fle c tio n loss
r a y AOA, t h e 9 9 . 8 %
the non-fading d ata
The 9 9 .8
% range
0.32 d e g .
was c o n s i d e r e d i n d e t a i l and i t was
under
very
d ue t o s u r f a c e
j
rough s e a c o n d i t i o n s ,
roughness
is
lim ited
to
the
a
a f ew d e c i b e l s .
During f a d in g c o n d i t i o n s ,
appear
to
in d icate
O t t e r L a k e p a t h was
reflectio n
T his
plus
is considered
th at
h e a v y f a d i n g on t h e A y l e s f o r d -
caused
the
by
effects
fu rth er
th e ray path c h a r a c t e r i s t i c s
-a
due
com bination
of
a
sea
to atm ospheric la y e r s .
in C hapter 6.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Chapter 6
MICROWAVE PROPAGATION ACROSS THE BAY OF FUNDY
- OTTBR LAKE TO NICTAUX SOOTH
6.1
In tro d u ctio n
Th e r e s u l t s
presen ted
the
in
th is
predicted
C h a p t e r .4.
1981 p r o p a g a t i o n
ch ap ter.
ray
These r e s u l t s
path
O tter
of m icrow ave
Lake
to
p ropagation
N ictaux S outh.
It
main d i f f e r e n c e * o f t h i s p r o p a g a t i o n p a t h
first
experim ent
ray is o ffe r e d
is
experim ent
p resented
in
used to i l l u s t r a t e
'a c ro ss
is
the
b ay
noted t h a t
f ro m t h a t
t h a t a good b lo c k a g e o f
by a m o u n t a i n
are
a re com pared-w ith
ch ara c te ristic s
The e x p e r i m e n t a l r e s u l t s . a r e
v arious aspects
from
froni* t h e
of
the
the
the r e f l e c t e d
r id g e c a l l e d N orth M ountain.
t
t
A ll
the u sa b le data g a th e re d
were in c lu d e d
approach
in
the
taken is
and _ t h e
m ajor
data
in
th e 35-day
experim ent
b a s e and w e r e p r o c e s s e d .
t h e same a s t h a t f o r t h e 1980
ray
path
ch .aracteristies
The
experim ent
for
the e n tir e
*
period
are
selected
included
periods’
in
A ppendix 7 .-
containing
Once
rep resen tativ e
again
resu lts
presen ted .
1 28
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
only
are
6.2
General Experim ental^Observations
In
the
equipm ent
1981
was
3rd Septem ber
the
w orst
region.
same
experim ent,
o perated
(Day 246)
fading
period,
Of
in
rem aining
32
radio
th is geo g rap h ical
th is
conducted
d ue
to
power o u t a g e s ,
- e v e n ts ' such
of
th e e x p e r im e n t showing th e
11 d a y s .
resu lts
The
6.1.
the tim e.
day b a s i s
fading
(marked
same i s
is
arrow s
observed
for
6.2 (b )
in o n ly fiv e
o b servations
geographical
suggest
days d u r in g
th at
r e g i o n .is c l o s e l y
amount
to talled
in F ig .
of
in
366
F ig.
three
6.2 (a))
the d i g i t a l ra d io
w hich
to
6 .2 (a).
occurred w ithin
when d i g i t a l r a d i o p e r f o r m a n c e was
occurred
equipm ent
The o c c u r re n c e of
shown
hours
by
sum m arized in F i g .
in th e
In sharp c o n tr a s t
t h e number o f f a d i n g h o u r s
the
d istin ct,p erio d s
as
are
and eq u ip m en t m a l f u n c t i o n .
e q u i v a l e n t t o 47 % o f
h alf
which'
No d a t a w e r e ' c o l l e c t e d
a c t i v i t y ,T s \ S h o w n i n F i g .
is
of
t h e t o t a ' l t i m e o f 809 h o u r s d u r i n g
f a d i n g h o u r s on a p e r
Over
t e s t was
>one
the
-A t i m e c h a r t o f
which
(Day 212) t t o
during
hours
1980 r e s u l t s ,
system
— a p e r i o d w hich i n c l u d e d
the d a ta b a se .
m aintenance,
the
31st Ju ly
777 h o u r s j p f d a t a w e r e c o l l e c t e d a l l o f
in clu d ed
fading
from
d iag n o stic
months o f t h e y e a r i n
The d i g i t a l
p erio d .
the
sh ow s
the
in
test
hours
d e g r a d e d . M o st o f t h e s e
the
35-dayp e r i o d .
severe
fading
a s s o c ia te d w ith
These
in
th is
cfianges
in
m eteorological* c o n d itio n s ” t h a t ta k e p la c e over p e rio d s of a
*
few d a y s .
It
is
noted t h a t
the am p litu d e
reference
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
(0 dB>*
Q
Q
Y
13 0
>
<J‘
*
ADT
O
Y
Aug.1 / 213
215
8/220
«
13/225
18/230
23/235
28/240
Sept.1/244
245
— non-fading
•— fa d in g hour
F r g .'6 .1
m o d e r a t e -j de g ra dat ion o n ^ h e
- severe
■digital radio
Time c h a r t o f e x p e r i m e n t a l o b s e r v a t i o n s
1981 e x p e r i m e n t .
9
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
fo r the
*
"O
JO
%
S 'S
20
o cn
o ■—
t “o
220
F ig.
6 .2
c *
*
230
Day. of y e a r
240
Summary o f 1 9 8 1 e x p e r i m e n t a l r e s u l t s
on a p e r day b a s i s .
The a r r o w s m a rk
th re e d i s t i n c t p e rio d s w ith heavy
fad in g .
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
for
the
%
am plitude
resu lts
o’f
non-fading
presented
the
m ain
in
t h i s c h a p t e r i s , th e m e d i a n
*
d alcu lated
from
the
1981*
ray
d ata base.
*
'
*
*
v
6 . 3 , Propagation During Non-Fading P eriods
^
^ '
*
Out o f th e 35-day p e r i o d ,
226,
and
237}
co ntained
o b t a i n e d o n Day 219 a r e
o n ly .th re e
no
fading
u sed .to
days
h o u♦r s .
illu stra te
durin g no n -fad in g p e r io d s .
0
From r a y t r a c i n g i t was p r e d i c t e d
(Days 2 1 9 ,'
T> h e c r e s u l t s
th e
propagation
co n d itio n s
a d irect
norm al
and a j r e f l e e t e d
'c o n d itio n s
am plitudes
estim ated
of
ray,
d esp ite
the
-
ray
in
a m p l i t u d e a nd
of
the
path
F ig.
ils s t a b l e
The
v a ria tio n s
.ray
th ro u g h o u t most o f
phase1 re c o rd ,
how ever,
A gain,
4 .4 .1 ,
*
Day 219
has
the*
are
a norm al
day.
The
shows s u b s t a n t i a l
c*
are
not
observed
in
the
th is
low a m p l i t u d e and s h o r t d e l a y
in S ectio n
re la tiv e
w e r e n o t c a u s e d b y g e n u i n e AOA v a r i a t i o n s
s in c e corresponding v a r i a tio n s
valu es.
a
r§ y were
a t 0 1 : 1 5 a n d 0 6 : 0 0 ADT.
•
in tercep t
w ith
a
for*
-d irect
th o u g h slow v a r i a t i o n s p a r t i c u l a r l y
These
reflected
The
tw o r a y s .
c h aracteristics
6 .3 .
path s,
blockage.
aS 0 ° dB a n d - 3 0 ' dB r e s p e c t i v e l y ,
sum m arized
slo p e
b etter
r a y ’and* t h e
d e la y tim e o f 4 .5 n s betw een th e
The
tw o r a y
w ould s t i l l b e O b s e r v e d u n d e r
th e
d irect
th at
s u g g e s ts the e x is te n c e of a
<■
0
ray p a t h .
As w a s p o i n t e d o u t
the p resen ce o f such
ray p a th s
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
has l i t t l e
Reproduced
with permission
of the copyright owner.
i ■
»
'•*
Vsv«~.lWA-**- -
Further reproduction
< -20
prohibited without p e r m is s io n .
06
00
03
' 09
12
18
15
21
Day 219
a Dt
aT - relative delay time.
A1/A2 - main(1) and second (2) ray amplitude.
AOAS / AOA1 - e s tim a te s of main ray AOA from slope (S) and .intercept (1).
Fig.
6.3
Ray'path characteristics on a non-fading day
experiment.
00
(219) in the 1981
l/i
W'
&
1 34
e f f e c t on
t h e main
in tercep t.
ray
However,
a m p l i t u d e and
the
phase
the
record
phase
slo p e
record
is
very
j
sen sitiv e
to
th is
found
is
reco rd slo p e
not
seen
these
is
in
ray p a th s .
at
One v e r y
23: 00 ADT.
good
A l a r g e s w in g
observed w h ile a
corresponding
the i n te r c e p t y a lu e .
The s l o p e
v alues
ar e. p l o t t e d
larg e
excursion
on an e x p a n d e d s c a l e
in
exam ple
in
in
of
the p h ase
change
is
a nd i n t e r c e p t
F ig .
6 .4 .
The
th e p h ase r e c o r d s lo p e a p p e a r s t o have
b e e n c a u s e d by a r a y p a t h t h e d e l a y o f w h i c h was v a r y i n g
tim e s im i l a r
As f o r
am plitude
to
the e f f e c t
the r e f l e c t e d
of
the
is
v a l u e by
flu c tu a tio n s
of
is
5 dB.
blocked
are
deg
by
d isp lay ed
a lso noted t h a t
-0 .2 5
has
ray a m p litu d e
s ho wn i n F i g . - 6 . 5 .
m ore e f f e c t i v e l y
It
it
a
fa v o u ra b ly w ith th e
reflected
the p re d ic te d
record
ray,
in F ig .
4 .12.
fairly
a p p r o x i m a t e l y - 2 5 dB a n d a d e l a y o f
T h e se v a l u e s compare
alth o u g h
illu strated
A
N orth
sweep
ray i s
only
m ild
t h e 1 GHz s w e e p r a n g e .
t h e m a i n and r e f l e c t e d
and - 0 . 5
values
frequency
the r e f l e c t e d
M ountain,
across
4.5 n s .
again h ig h e r £han
ty p ical
Because
stab le
pred icted
is
in
r a y AOA v a l u e s
deg c o m p a r e w e l l w i t h t h e v a l u e s o f
- 0 . 2 3 d eg a n d - 0 . 5 8 d e g p r e d i c t e d
for
a uniform
N -gradient
o f - 4 0 NU/km ( s e e C h a p t e r 4 ) .
The d i s t r i b u t i o n s o f
am plitudes
-fading
and
data
reflected
ray
th e d e l a y tim e were com puted u s i n g a l l
th e
as
the
d irect
t h e ■d a t a b a s e .
presen ted
in
F ig s . 6 .6 (a)
to (c ).
d i r e c t and
r e f l e c t e d ray am plitudes
and
The
M edian
resu lts
are
values of
the
and t h e d e l a y
it
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
tim e
are
.
Reproduced
with permission
of the copyright owner.
CL
0.20
0.22
2 -0.24
Further reproduction
or
prohibited without p e r m is s io n .
Q-
0.2
o> c
Of c
■o o
0.6
2300
Day 219
F ig.
.
6.4*
2305
2315
2310
2320
2325
ADT
S p u r i o u s v a r i a t i o n s i n t h e p h a s e r e c o r d s l o p e c a u s e d ' by t h e
p r e s e n c e o f a , s h o r t d e l a y r a y "with a s l o w l y v a r y i n g , d e l a y tim e ,
135
136
1
r
r
1
l
1----- 1----- r
H
1------ 1-------1------- \-
0m
X)
ct -10
■o
3
Cl
£
< -20
f - + -
h
U>
at
TJ
*180
a
JZ
«
a.
i
at
|
90
at
a.
1
10.0
9.5
Frequency
L
10.5
( GHz )
1
Am pl.(dB)
F ig.
AOA ( d e g)
Delay (ns)
-1.1
-0.25
-
-25.0
-0.50
4.5
6.5
— r e f l e c t e d ray
E x p erim en tal (d o tted ) and s y n th e s iz e d
d a t a r e c o r d act 0 0 : 0 0 : 0 5 ADT o n Day 2 1 9 .
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Reproduced
with permission
(a)
0 .2-
0.2-
of the copyright owner.
i
.2 0 .1-
a.
Further reproduction
*
0
-10
-20
-30
lain ray amplitude (dB)
Rel. delay
Ins)
0 . 2-
prohibited without p e r m is s io n .
c 0.1-
0
-10
-20
-30
Second ray amplitude (dB)
Fig.
6.6
Distributions of the ray amplitudes and relative delay time
for the 1981 non-fading data.
\
\ 37
0 dB, - 2 0 .9
values of
d B , and 4 . 7
the
stan d ard
ns r e s p e c t i v e l y .
d ev iatio n
The c o r r e s p o n d in g
f r o m t h e mean a r e
2 . 3 dB ,
a
p o in ts.
5 .0 dB, and 1 .0 ns r e s p e c t i v e l y .
These
resu lts
*
illu strate
few
im portant
..
F irst,
N o r t h M o u n t a i n d o e s p r o v i d e a m ore a d e q u a t e t e r r a i n
t
b lo c k a g e to the
sea
reflectio n ,
at
least
under
normal
co n d itio n s.
T his
am plitud e of
m edian
the
resu lted
reflected
am plitude
of
p red icted
value
experim ent,
\
causes.
o f - 3 0 dB.
first
of
12 m)
used
the
resu lts
both
terrain
it
average
to
is
attrib u ted
i^
both
[23].
for
to
the
the
first
m ajor
th e u n c e rta in ty
in th e
average t r e e
estim ate.
do
h eig ht
I n any e v e n t ,
suggest
h e i g h t o f 12 m i s
in
than
tw o
the
suspected
m edian
experim ent).
h ig h er
As was t h e c a s e
th at
the
too h igh a v a lu e .
th at^ ^ th e
cases
th a t of a knife-edge
terrain
first
9 dB
(in c lu d in g
also
stru ctu res
c h aracteristics
for
is
reduced
dB ( c o m p a r e d w i t h a
the
experim ents
assumed e q u i v a l e n t t r e e
F u rth erm o re,
is
in t h e d i f f r a c t i o n
from
much
for
th ese
h e i g h t o f N orth M ountain
of
dB
how ever,
th is d iscrepancy
The
a
ray o f -2 0 .9
-1 2 .6
T h is m edian a m p litu d e ,
in
d iffractin g
are
than
clo ser
was
in
assumed
The s e c o n d m ajor c a u s e o f th e
'■S
d iscrepancy a ris e s
path
c h aracteristics
- 4 0 NU/km.
summer
from t h e f a c t
S ince
m o n th
in co n ceiv ab le
in
th at
th at
the
pred icted
ray
were b a s e d on a m edian N - g r a d i e n t o f
the experim ent
was
perform ed
a re g io n w ith M aritim e c lim a te ,
d u rin g
it
is
a
not
t h e - m e d i a n g r a d i e n t may»be more n e g a t i v e
t h a n - 4 0 NU/km, t h u s r e s u l t i n g
in a h ig h e r
am plitude o f the
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
reflected
ra y due to
M ountain.
Such
increased
path
appeahs^ ' t o
be
clearance
at
N orth
t h e c a s e on Day 237 when
h ig h e r th a n norm al v a lu e s of th e
d elay
tim e,
d irect
ray
4
'
' AOA,
an d
reflected
A p p e n d ix '7 ) .
ray
am plitude
d irect
by
p e rio d s of a w prst f a ^ n g
stu d y in g
the
fange in
same
d istrib u tio n
m ethod
used
6 .7 (a)
a nd
The d i s t r i b u t i o n
the
d irect
resp ectiv ely .
0.47
'
deg.
refractiv ity
The
T his
,
for
the
as
%
tra n slates
-
‘
% and t h e 9 9 . 9
-0 .4 2
range
.Tjhe
in tercep t
1980 r e s u l t s .
"
AOA
99.8
r a y AOA.
non-fading d a ta
(b).
the
m o n t h , may b e o b t a i n e d
the
g iv e s th e 0.1
ray
d u rin g
f r o m t h e phase- r e c o r d
o f t h e AOA f o r
show n i n F i g s .
of
ov erall
the observed d i r e c t
r a y AOA was o b t a i n e d
the
(see
-
e n c o u n t e r e d ' on t h i s p r o p a g a t i o n p a t h ,
non-fading
by
evident
'
An e s t i m a t e o f t h e r a n g e o f t h e
g rad ien t
are
in
d eg
The
base
is
•
% values
a n d ' 0 . 0 5 d eg
AOA t h e r e f o r e
is
t o a 9 9 . 8 % r a n g e i n N-g‘r a d i e n t
>
'
o f - 1 6 L < diq/dh < 4 0 . 2 NU/km ( o r - 4 0 < K < 0 . 8 ) .
T h e 9 9 . 8 % r a n g e i n AOJWof
-
qui€e
sm all
w ith E q .
and
comjpafced
(2.9)
'0 . 4 7 deg
is
seen
to
be
•*
*
w ith t h e r a n g e o f 1 .6 deg e s t i m a t e d
a nd u s i n g dto /dh v a l u e s p b t a i n e d
B arrin g to n
[3].
The
apparently larg e
<v
r a n g e i s ■e x p l a i n e d by t h e f a c t
*
1
dN/dh
obtained
the ^ i r s t
f r o m S e g a l a nd B a r r i n g t o n
100 m i n t h e a t m o s p h e r e .
p ath h o w e v e r,
w ithin
th a t the
the h e ig h t
W
"
d ictates
th at
from
e s t i m a t e d AOA
99.8
% values
in
are
tab u lated
for
The a c t u a l
th e, d ire c t
propagation
ray p a th l i e s
r a n g e f r o m 100 t o £00 m abov e„ M S L,
*
”
'
•
Segal
rr '
R e p r o d u c e d with p e r m i s s io n of t h e co p y rig h t o w n e r. F u r th e r r e p r o d u c tio n prohibited w ith o u t p e r m is s io n .
W hile
Refractivity gradient
0
(N U /k m )
s -100
-200
a)
o
Main ray AOA
(deg)
— 100
— 50
c
-0
o
X
-5 0
0.01
P ercentage of tim e AOA e x c e e d e d .
F ig ,
6.7-^ D i s t r i b u t i o n o f t h e m a i n r a y AOA f o r t h e
19 8 1 n o n - f a d i n g d a t a .
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
gradient
T>
Refractivity
— 150
(N U /km )
(b)
the
extrem e
N -g rad ien ts
used
f
a h e i g h t s clo^ef to th e s u r f a c e o f
lik ely
are
p
the
t h a t such extrem e g r a d i e n t s
*
f u l l height
range
*
unreasonable
at
*
it
seem& l e s s
are m a in ta in e d over the
•
rf
in c o n s id e r a t i o n .
*
6.4
not
‘
bay,
“
Anomalous P r o p a g a t i o n
A lthough the p r o p a g a tio n c o n d itio n s " d u rin g
highly
v ariab le,
certain
fading
ray path c h a r a c t e r is t i c s
are
ap pear to
<5
b e commonly o b s e r v e d d u r i n g ,
point
is
illu strated
- (13th A ugust)
and 242
A p lo t of
these,
fading
by t h e ' r e s u l t s
p erio d s.
obtained
f r o m Days 225
(30th A u g u s t).
the ray p a th c h a r a c t e r i s t i c s
%
f o r D a y ^ 225
sh own i n F i g . 6 . 8 .
The m ost n o t i c e a b l e f e a t u r e i s
/
d e l a y t i m e o f t h e r e f l e c t e d r a y sh ow s
a gradual
from
a
normal
value of
d e c r e a s e s slo w ly back
The
same,
to th e normal v a lu e
i s -observed fo r
o c c u r s when t h e d e l a y t i m e i s maximum.
hand,
'th e
increased
du rin g
'—
th e tim e
by
fading
o b se rv e d in th e m orning.
r e f l e c t e d ’’ r a y
more
it
%
AOA a l s o
are
am plitude
the
increase
t h e m a i i j f r a y AOA w h i c h i s
S u b s t a n t i a l e n h a n c e m e n t and r a p i d
is
then
in th e a f te rn o o n .
n o rm a l^.v alu e o f - 0 . 2 3 deg to 0 . 1 d e g .
am plitude
th at
4 n s t o more t h a n 8 ns>.,
from i t s
ray
T his
. is
t h a n 15 dB a b o v e i t s
raised
The h ig h e s t
in
the
main
. On t h e o t h e r
su b stan tially
normal v a l u e ,
f r o m 0 9 : 0 0 t o 1 2 : 0 0 ADT.
t
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
*
Reproduced
with permission
d ig ital 1
rad io
i
J
1i
i
i
1
r
f-------- r -— »------- 1--------1--------7--------r
of the copyright owner.
8-
in
t-
jX
4-
4
4&1.
- OJ
£
s
0 -
r»
- 2 0 -
Further reproduction
* <
-I— I— I— I— h
m
-o
0 -
INI
- 2 0 -
<
H
A
1--------1--------1-------- \r
1---- 1---- 1---- 1---- 1---- 1---- 1-
prohibited without p e r m is s io n .
1
1_
1
-»
Ol
2
0 in
< -D.Ao
<
"S' 0 a»
■o
- 0.2 <
O
< -0,4-
ifm r f '
,,‘
*
_i I*. 1
,00
.Day 225
’■
03
. »y i
■.1
i . - , , t ... - i '
06 •
»■■- ! ■
09
S’ t—
-■%»*
* —1
12
ADT
«
i .
I
15
I
21
relative dela} time.
•
A1/A2 - main(1) and second (2) ray amplitude.
v ADAS / AOA1 - estim ates of main ray AOA from slope (S) and intercept (I).
Fig.
aT -
-1^, ■I
6.8
Ray path characteristics on a fading day
1
00
,
(225) in the 1981 experiment,
-b.
ro
These observed ray p a th c h a r a c t e r i s t i c s
very
siftilar
to
those
observed fo r
the
^
are
in
1980 e x p e r i m e n t .
/
R ecallin g
the e f f e c t s
discussed
path
in
of
atm ospheric
S ection 5 .5 .1 ,
featu res
of:
(a)
it
is
'
layers
seen t h a t
decreased
fact
main
which
were
t h e g»ross r a y
ray
am plitude,
v>
(b)
elevated
am plitude,
all
be
main
and
ray
(d)
( c)
su b stan tially
explained
occurring
AOA,
by
increased
in c re a se d d elay
p o s t u l a t i nt g.
below t h e a n t e n n a s .
reflected
*
an
tim e,
atm ospheric
The long d e la y
ray
may
layer *
tim e o f
more
T
th at
8 ns
in
th is
case is
accounted fo r
by t h e i n c r e a s e d
a n te n n a h e i g h t s in th e O t t e r Lake - N ic ta u x South p a t h .
of
T h e f a d i n g o b s e r v e d on Day 225 i s i n f a c t
an e x a m p l e
*
relativ e ly
m ild
fading
in
t h e ,1981 e x p e r i m e n t .
The
^
*
f a d i n g o n ly c a u s e d m ild d e g r a d a t i o n on
perform ance
fading
day
(at
05:00,
d uring
10:00,
the
expetim ent
the
F ig.
€ .9 .
,
*
The r e l a t i v e
^
g reater
than
flu ctu atio n s
, observed. '
relativ e
The w o rs t
is
when^ t h e ,
Day 242
'
im paired.
f o r D a ^ 242 a r e shown
in
tim e o f th e r e f l e c t e d r a y i s
,
v
the
day,
w ith
a maximum o f
>
09:0(V ^DT.
Onc e a g a i n
rap id ,
of
10 n s / a t
^
in b o t h t h e main and se c o n d r a y a m p l i t u d e s a r e
The
to
^
delay
\
above 6 ns d u r in g most
radio
1 1 : 0 0 ADT).
o p e r a t i o n o f t h e d i g i t a l r a d i o , was s e v e r e l y
The ray p a t h c h a r a c t e r i s t i c s
d ig ital
its
main
ray
normal
fades
value
a t t i m e s t o b e l o w - 2 0 dB
(e .g .
at
1 3 : 0 0 ADT).
*
F urtherm ore,
s i g n a l e n h a n c e m e n t s o f ^as h i g h a s 10 dB a b o v e
normal
a t 2 1 : 0 0 ADT)
(e .g .
are
observed.
The
reflected
*
ray,
on t h e o t h e r h a n d , s h o w s an i n c r e a s e d s i g n a l l e v e l —
m
>
‘
<o
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Reproduced
with permission
.
"I
11
i
1i
t
"1 i
I 1 ".I ~F~
r
-I
V r' I
*
r-
1
of the copyright owner.
y .
V)
Q
S
4
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-t
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00
TJ
F -H
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-F
1
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H
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F
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I “ I----- F
JO.
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t :■■■■.■.■■■| . .. _ |_ ■■J . . ■- I
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C
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in
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03
06
09
12
15
18
21
00
00
Day 242
a DT
* aT - relative delay timne.
'
^
•A 1ZA 2- main(1) and second (2) ray amplitude.
AOAS / A0AI - estim ates of main ray AOA from slope (S) and intercept (I).
''
'
■
•
F ig . 6. 9
Ray j o a t h characteristics on the woi'st fading day ( 242) in the
119 8 1 experiment.
*
A.
A
a t t i m e s by m ore t h a n
10 dB
exceeds
fray a m p l i t u d e
the
d ire ct
•
ray .'
,r e s u l t s .
its
norm al
lev el
to dom inate as
'
and
t h e m ain
*
These p e rio d s
- recallin g
above
are
th a t , the
read ily .id e n tifie d
stro n g er
Such b e h a v io u r
is
ray
w ill
observed,
•
i n t h e AOA
dom inate
for
p lo t
t h e AOA
exam ple.,
from
•
b 2 : 0 Q ADT t o . 0 6 :0 0 ADT,
A sweep f r e q u e n c y
analysed
by
shown i n
across
and a l s p
from 0 8 :3 0
record o b tain ed
t p * . l l : 0 0 ADT.
a t 1 0 : 0 4 : 5 2 ADT
t h e r p a t t e r n s y n t h e s i s m ethod and
R ig.
t h e 1 G#z
6 .1 0 .
As e r i e s ' o f n i n e
frequency
band
was
th e .re su lts
n u lls
is.o b se rv ed
d ue td* t h e
d estru ctiv e
•»
in te r f e r e n c e between th e d i r e c t
Two \ £ t r o n g <
ray
*'
p ath s
-
d irect,
ray
elev ated
th e
r e f l e c t e d , ra y s .
id en tified .
In p a rtic u la r
.
*
am plitude
AOA
irtcreased
#a r e
and
is
o f e 0 .“02 dec^.
am plitude,
of
-8 .9
.
reduced to
-1 0 .8
The
reflected
dB
and
a
dB
w ith
h igher
AOA
d&g
(com pared w ith th e norm al v a l u e s o f - 2 0 .9
* "- * *
■
*
'
* - 0 . 5 ’s f d e g ) .
The
delay
tim e
o f - 9,.2 a n s
is
also
-very
.
V .
A l s o sh o v m * in P i g . 6.10- a r e ' t h e
i *
d eg rad atio n
occurred
pn
the- d i g i t a l
tim es
w h en
rad io .
"
severe.
V ery good
'
c o r r e l a t i o n s .o f d i g i t a l ra d io o u tag es w ith :
tim e s ,
of
dB a n d
sig n ific a n t.'
'
an
r a y h a s a mu ch
. -0 .4 3
r
th e
»
and
(a) long d elay
(b) p e rio d s ^when th e d i r e c t ray am p litu d e was
reduded to below
th e
le v e l
of
th e , r e f le c t e d
e s p e c ia lly e v id e n t from 02:00 to 13:00 ADT.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
ra y ,
are
146
o CD
*
T3
-10
3
Cl
e
< -20
-|
cn
o>
TO
180
o<
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1-------1----- - +
-
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Cl
41 °
> 90 - * /
a
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tr
V
W
Q.I— 1--------1----- _l_____ I--------1— :— I. ------ I--------L.
,
, .
10.0
9.5
10.5
o
Frequency
*
«3Hz)
i
k
A O A jd egf
Am pl.(d^)
«
-103
- 8 .9
F ig.
6.10
?
.
Delay (ns)
' *•
0.02
-0.43
9.2
— reflected ray
E x p e rim e n ta l (d o tte d ) and s y n t h e s i z e d '
d a t a r e c o r d a ^ 1 0 : 0 4 : 5 2 ADT on Day 2 4 ^ .
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
1 47
6 *5
A tm ospheric L a y ers
A tm ospheric
g rad ien ts
of
-
lay ers,
w ithin
refractiv ity ,
are
which
ex ist
t h e m a j o r c e r u se s o f
f a d i n g a c r o s s t h e Bay o f F u n d y i n h o t h t h e
experim ents.
The
influence
extrem e
of
198 0
severe
a nd
1981
t h e s e l a y e r s on m i c r o w a v e
p r o p a g a t i o n a r e now e x a m i n e d i n m o re d e t a i l .
The o c c u r r e n c e of ' m u l t i p a t h
propagation
associated
j
•
c
w i t h a t m o s p h e r i c l a y e r s was d i s c u s s e d i n S e c t i o n 2 . 4 . 2 .
In
a
<
t
the e x p e rim e n ts p r e s e n te d in t h i s t h e s i s ,
there
e x i s t s an
i
|r6 ded
com plication.
In S e c tio n 5.4 v a r io u s a s p e c ts of th e
sea r e f l e c t i o n
have b e e n e x a m in e d .
except
.very ro u g h s e a c o n d i t i o n s ,
under
is f a ir ly
on
stab le
microwave
was
a nd i s o n l y a t t e n u a t e d
reflectio n .
resu lts,
It
As
is
presen ted
concluded
th at
the r e f le c te d
ray
by a
in
fe w
the
decibels
experim ental
t h i s s e a r e f l e c t i o n p l a y s an i m p o r t a n t
ro le
in
*
’ ,
propagation
across
the
bay, e s p e c i a l l y d u rin g
a
p e rio d s of severe fa d in g .
»
f
To i l l u s t r a t e
lay ers
for
and
the
the O tte r
layer
W ith
the
combined
sea r e f l e c t i o n ,
Lake param eters
¥
effects
of
ray tra c in g
N ictauxSouth
6
AN 3 - 4 0 NU
atm ospheric
was p e r f o r m e d
propagationp ath .
'
and
A
Ab 3 100 m was
•
assum ed.
The h e i g h t
the
antenna
(ti
3 200 m ) ,
O
h ig h -lev el
to
<
h eigh ts.
o f t h e l a y e r was v a r i e d
The
**
re la tiv e
r e s u l t s fo r a low -devel la y e r
a m id -lev el
layer
( h 3 260 m ) ,
to.
o
0
layer
(h 3 380 m ) , a r e show n i n F i g s .
(c).
1
*
to
'
■ :
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
and
a
6.11(a)
1 48
-0.17'
300
-0.4S1
200
100
cn
M
00
00
00
00
lb)
400
_J
CO,
■0. 01'
Z
300
&
jO
O
200
£
100
20
9
40
400
CO
0.11*
•
0.20
300
-O.I3'
200
-0 J 7
100
M, 10 NU/div.
Fi<f;
30
00
00
Distance ( km)
6 .1 1 P r o p a g a t i o n on t h e O t t e r ' L a k e - N i c t a u x S o u th
p a t h when a n a t m o s p h e r i c l a y e r i s p r e s e n t a t
v a r i o u s h e i g h t s : (a ) l o w - l e v e l l a y e r
(b) m i d - l e v e l , l a y e r , (c ) ' h i g h - l e v e l l a y e r .
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
149
• «
When t h e l a y e r i s irar b e l o w b o t h a p € « n n a s ,
»
F ig.
6 .1 1 (a), i ts
effect
•« '
d i r e c t 'rayi s m in im a l.
‘
i
N orth
the
3
' ^*
r a y , w h i c h i s n o r m a l l y wfell
However, t h e r e f l e c t e d
by
on
a s shown i n
M ountain,
is
blocked
t
"lifted "
due t o th e p r e s e n c e o f th e
9
*
th at
the
clearan ce , fo r
the
"*
lay er.
The n e t
reflected
resu lt
ray
is
is
v
increased
and t h i s i n t u r n l e a d ^ t o * a n
*.
E xperim ental
evidence
of
th is
*
increased
am plitude.
behaviour
i s found in th e r e s u l t s p r e s e n t e d in S e c t i o n 6 .4
f o r b o t h Da ys 225
( f r o m 0 8 : 3 0 t o 1 3 : 0 0 ADT)
most o f th e d a y ) .
the
relativ e
ray.
The r e s u l t
delay
tim e
again f re q u e n tly observed
tim es
index v a lu e
has th e e f f e c t o f i n c r e a s i n g
the re fle c te d
of
greater
long d e la y
tim es
242
(over
below
the
lay er
'
The e n h a n c e d r e f r a c t i v e
also
and
the phase p a th le n g th
is
of
a s u b s t a n t i a l i n c r e a s e in
i
the r e f l e c t e d
experim ents
tim e
lay er is
fop
delay
t h a n 10 n s w e r e f o u n d on d a y 2 4 2 .
»
These
the
placed
F i g . IF. 1 1 ( b ) ,
im portant
bearings
reflected
ju st
In
on
th is
below
the
case
ex p erim en tally
observed
-
the
error
in creased
r a y a r e o b s e r v e d when t h e
antennas
as
showf\,
in
t h e r e i s an a d d e d e f f e c t o f
stro n g d efo cu ssin g o f the d i r e c t pay.
. the
T his is
and
have
for both
ray.-
perform ance o f d i g i t a l ra d io sy stem s.
■ *
T h e same e f f e c t s e*f i n c r e a s e d c l e a r a n c e and
delay
of
T his
reduction
accounts
for
in th e d i r e c t ray
;
am plitude.
.
4
When t h e l a y e r i s
antennas,
present
atm ospheric m u ltip a th
at
a
h e i g h t t above
both
is observed in a d d itio n to
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
150
the
reflected
atm ospheric
described
ray
in
observed
ray
as
shown
p aths
are
not
S ection 2 .4 .2 .
in
the
in
P ig.
6.11(c) .
d ifferen t
These
ray
experim ental
The
from th e ones
paths
resu lts.
are
A
also
d etailed
j
d i s c u s s i o n o f th e b e h a v io u r o f such a tm o s p h e r ic
in
relatio n
to
atm ospheric
la y e r param eters
ray
p aths
i s found in
*
W ebster
[43] .
The above r e s u l t s
shows*
the
received
effects
of
lay er
(a )
elev ated d ire c t
in c re a se d d elay
clearance,
and
d efocussing,
tim e,
(d)
(c)
Fig..
6.12
v a ria tio n s
w hich
on
the
The im p o r ta n t r a y ^ p a t h
and r e f l e c t e d
increased re fle c te d
reduced
are noted
in
h eight
ray path c h a r a c t e r i s t i c s .
behaviour o f:
(b)
a re sum m arized
d irect
ray
r a y AOA's,
I
ray
path
am plitude d u e 'to
f o r c a s e s when t h e
lay er
is
below
both an ten n as.
A lso of i n t e r e s t
a r e ±4fie r a y p a t h c h a r a c t e r i s t i c s
the atm ospheric rays l a b e l l e d
2 and 3.
a t m o s p h e r i c r a y p a t h s w o u l d be
*
•la y e r.
It
present
is
for
•»
s e e n t h a t tw o
a
^ ig h -lev el
*
Ray, 2 h a s c o m p a r a b l e ' a m p l i t u d e t o
,
for
th e n orilpl d i r e c t
*
r a y w h i l e r a y * 3 c a n t a k e up v a r y i n g a m p l i t u d e s d e p e n d i n g on
*
1
•
’
1
the .la y e r h e ig h t.
I t is a ls o hoted th a t th e se atm o sp h eric
. r a y p a t h s h a v e h i g h e r AOA’ s t h a n t h e n o r m a l r a y
* *•
, »
\
a nd
f «
th eir
relativ e
delay
tim es
c a n , r a n g e from n e g a t i v e t o p o s i t i v e
*
*
' *
v a l u e s o f up t o 5 n s *f o r . . t h e d u c t * u As e d i n t h e e x a m p l e .
'*
*
U sin g F i g . 6.12‘ h a a cfuida, t h e
fexperim ental
resu lts s
for
D ay s 225
D uring
and
the p e r io d
242
i» re
-exam ined
in'
f r o m 0 3 : 0 0 t;o 0 6 : 0 0 AD£ o n
fu rth er d e ta il.
Day 225
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
(see
1-
151
N 0
:
3 0 0
N U
d N / d h :
- 4 0
N U / k m
A
- 4 0
N U
N
;
Ah :
100 m
Ground
Height a t
N orth Mtn
5 ' * 1 7 0
a
,*
o is o
**■
Layer H«%ht (m) aftave mean sea level
F ig.
•
6.12
E f f e c t s o f l a y e r h e i g h t v a r i a t i o n s on r a y
p a t h c h a r a c t e r i s t i c s f o r t h e Ottfer Lake ~
N ic ta u x South p a th .
R. , . . r e f l e c t e d r a y . ’
[44]
, •
.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
152
F ig.
6.8 ),
an
extra
d irect
a nd r e f l e c t e d
delay
tim e
ray
rays)
path
is
(in a d d itio n
p re se n t asis
ch aracteristics.
The
of
the R eflected
frequency records
AOA
of
A lso,
ray.
reveals
approxim ately
7"
the a m p litu d e of
A n aly sis
th at
the
0 deg
the
th e norm al J
evident
is
higher
the
tha*^
o f some o f t h e s w e e p
e x t r a ray
p ath
has
and an a m p l i t u d e o f
normal
in
e x t r a ray has a d e la y o f
^4 n s a t 0 5 : 0 0 ADT Shd an a m p l i t u d e w h i c h
* th at
to
ray
was
an
- 1 2 dB.
found
'to
be'
&
- 7 dB .
A l t h o u g h t h e AOA's and d e l a y
3 by a s i n g l e l a y e r , a t
reduced
ray
second
layer
defocussing
for
at
the
h eig h t
tim e can be e x p l a i n e d
of
the
antennas,
th
» -V'
p a t h > a m p l i t u d e s do s u g g e s t , t h e p r e s e n c e t> f.a
k
*
below
the
antennas' th ereb y
causing
the
i n t h e tw o a t m o s p h e r i c p a t h s .
. F u r t h e r "’i n s i g h t ' l i l a y asLso be g a i n e d
"
' *•
Day 242 shown i n F i g . 6 . 9 .
F irst,
*
from
it
^he
is
resu lts
observed t h a t
1 1 : 3 0 ADT, b o t h t h e d e l a y t i m e a n d t h e a m p l i t u d e o f
reflected
ray
v a l u e s down t o
,
the
show a r a p i d d r o p f r o m e x t r a o r d i n a r i l y h i g h
th e normal v a l u e s .
B a s e d on*
F ig.
6'. 1 2 ,
it
%
appears
t h a t f r o m 0 8 : 0 0 t o 1 3 : 0 0 ADT, t h e l a y e r h e i g h t was
increasing
slo w ly .
The
rapid
1 1 : 3 0 ADT t h e n c o r r e s p o n d s
antennas are w ith in
drop
in
d elay
tim e
at
to a l a y e r h e i g h t such t h a t b o th
the l a y e r .
The r e s u l t s
in d icate
a subsequent decrease
below th e
a n te n n a s from 13:00
after
1 2 : 3 0 ADT
in t h e l a y e r h e i g h t to j u s t
to
1 4 : 0 0 ADT,
thus
causing'
sr-
th e s u b s ta n tia l decrease
i n t h e d i r e c t r a y by d e f o c u s s i n g .
■#-
A lth o u g h t h e model o f a l a y e r
h eight
seems
to
risin g
adequately ex p lain
and
fallin g
in
th e observed ray path
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
ch a ra c te ristic s,
it
is
again noted t h a t
the
model
of
an
id e a liz e d
layer
w ith w ell d e fin e d b o u n d a rie s is a t b e s t a
'•*
*
$
■<
sim p lified
p ictu re.
It
is
not
in conceivable
th at
S '
o
v ag i^tio n s
in
the
layer ^ h e ig h t
c a n be
a c c o m p a n i e d by
changes in th e la y e r s tr e n g th
as
an
a?
thick ness
Ah.
F u rth erm o re,
w ell as th e
anom aly
’
layer
param eters,
are
not
e x p e c te d .to be
length
h o riz o n ta lly
homogeneous
al o n g * t h e
fu ll
**
*
the"* p r o p a g a t i o n p a t h .
D i f f e r e n c e s betw een th e
of
ex p erim en tally
param eters
4
*
observed
»
a nd
the
are thus a t t ^ i ^ u t e d
m odelled
ray t
to d e v ia tio n s
path
in tb g ^ atftu al
•*
atm osphere
from t h e , i d e a l i z e d
A rough e s t i m a t e o f
the,
la y e r's t-rv c rtfffe .
layer
stren g th
co m m only
an
a
observed1 i ^
maximum
the
d elay
illu strated
Bay
value
by
of
of
Fundy
the
assum ing
ma‘y b e i n f e r r e d
reflected
a
lay er
ray.
T his
is
w i t h anomaly t h i c k n e s s
, J
#
fro m ' t h e
*
Ah = 100 m and a h e i g h t w h i c h w i l l c a u s e - m a x i m u m
the
O tter
Lake
v a r ia tio n of
for
-
N ictaux
th e d e la y tim e v e r s u s
€his la y e r h e ig h t is
diagram ,
deldy
the s tr e n g th o f
of
a
stren g th
10 n s .
th e
path
reveals
245)
r
1
shown i n F i g .
the la y e r
,
lay er
stren g th
6 .13.
th at
o
AN
B ased on t h i s
caused
t h e l a y e r o b s e r v e d o n Day 242 was
delay o f
jgay
the
a
maximum
8 n s on Day 225 w a s e s t i m a t e d t o b e AN = - 2 0 NU.
S im ilarly ,
have
delay
on
fa
S o u t h path, ( h Q = 260 m) . T h e
of
aN
- - 3 0 NU s i n c e
it
By t h e same r e a s o n i n g ,
ch aracteristics
(at
t h e maximum d e l a y o f t h e r e f l e c t e d
r
*
,•
;
in
of
A ppendix 7
2 3 ? 0 0 ADT
-
to
c a u s e d a maximum
an e x a m i n a t i o n
sum m arized
t h a t e x c e p t on o n e o c c a s i o n
estim ated
on
Day
ray did not exceed
.
;*V'
e>
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
1 54
Layer’h e ig h t , h, = 260 m
Anomaly thickness, a h = 1 0 0 m
©
>
-10
Fig.
6.13
-2 0
a N , la y e r
-30
stren g th
-AO
(,NU)
-50
-60
The maximum r e l a t i v e d e l a y o f t h e i n f l e c t e d
r a y c a u s e d by a s i n g l e l a y e r w i t h s t r e n g t h AN.
fc
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
155
12 n s ;
of
therefore
elevated
it
i s concluded t h a t th e
lay ers
e x c e e d s - 4 0 NU.
observed
in
layer
stren g th
t h e Bay o f F u n d y r a r e l y
F o r t h e p e r i o d fro m 2 3 : 0 0 ADT
on
Day 245
t o 0 1 : 0 0 ADT on Day 246, t h e d e l a y t i m e h a s a maximum v a l u e
*
*
o f j u s t ab ove 14 n s , t h e c o r r e s p o n d i n g l a y e r
stren g th
was
e s t i m a t e d t o be a p p r o x i m a t e l y - 5 0 NU.
•
6.6
5
Ray P a t h S t a t i s t i c s
4
The s t a t i s t i c s o f t h e m ain and s e c o n d
ray
am plitudes
and o f ^ h e d e l a y t im e d u r i n g f a d i n g wer e c o m p u te d u s d n g t h e
366 f a d i n g h o u r s o b t a i n e d
i n 1981 a s t h e
r e s u l t s a r e s u m m a r i z e d %in F i g s .
6.14(a)
a m p l i t u d e s o f t h e m a in and r e f l e c t e d
- 4 . 0 dB
and
- 1 8 . 9 dB
(compared
- 2 0 . 9 dB r e s p e c t i v e l y f o r
found
fro m
the f i r s t
the
data
to
ray
base.
(c) .
T h e m e d ia n
w ere f o u n d
w ith
more
non-fading
experim ent, severe
im portantly,
main • r a y a m p l i t u d e .
by
to
data).
As
also
#
was
fading ap p ears to
am plitude,
a s ig n if ic a n t decrease
The r e s u l t s
be
v a l u e s o f 0 dB and
b e c a u s e d n o t m e r e l y by an i n c r e a s e d s e c o n d r a y
but,
The
support
the
in th e
model
<<
t h a t a t m o s p h e r i c l a y e r s , w h i c h c a u s e f a d i n g i n t h e mai n r a y
‘and e n h a n c e m e n t s i n t h e , r e f 1 e c t e d r a y ,
<
a r e t h e m a in
causes
•
o f s e v e r e f a d i n g a c r o s s t h e Bay o f f u n d y .
,
The-ray path s t a t i s t i c s
p eriods
are
compared
paper.
The
delay
by " p l o t t i n g
tim e
?
d uring non-fading
on
fading
Normhl P r o b a b i l i t y
sta tistic s
shown
;
• \
'
and
in
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
F ig.
6.15
Reproduced with permission of the copyright owner. Further reproduction
(a)
0 .1-
11.
-30
Main ray amplitude (dB)
6
C
R e l. d e la y
8
,
10
(n s )
(b )
prohibited without perm ission.
: 10
0
-10
-20
Second ray amplitude (dB)
Fig'. 6.14
Distribution of the ray amplitudes and relative delay time
for the 1981 fading data.
156
1
*
157
e
is—
<10
1981
—
fading
5—
non-fading
00.-01 0.1
5
,50
10
99
9,9.9
99. 9 9
P e r c o n t a g e , of t i m e AT* m c e e d o d
F ig.
6.15
D i s t r i b u t i o n o f th e r e l a t i v e d e la y tim e ,
o f t h e r e f l e c t e d r a y i n t h e 1981
e x p e r i m e n t p l o t t e d on. N o r m a l P r o b a b i l i t y r
paper. *
\
•<v
\
\
• S
*#
~
-%
*
'
'
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
'N
158
' *
o
£
,
ind icate
an
fading.
o verall
increase
The mope* i m p o r t a n t
m edian
delay
fading d ata,
increased
by
tim e
is
in
po in t
increased
the d k lay
tim e
the
delay
is
th a t although
by.
o n l y 1.1* n s f o r t h e
for
alm ost 3 n s .
time d u r in g
Af th e
the
tim e
The e f f e c t o f long d e l a y
is
tim es
X
on
d ig ital
*
radio
perform ance
C hapter 8.
w ill
♦
be
d iscu ss'ed
■*
v
' “
T h e main and s e c o n d r a y ^ a m p l i t u d e s t a t i s t i c s
•
tor
the
non^-fading
and f adi-n g . d a t a a r e c o m p a r e d i n F i g s . 6 . l 6 „ ( a )
*•
*
\/-and (b) . , Th e. t h e o r e t i c a l d i s t r i b u t i o n o f t h e - r e s u l t a n t
of
a
j
a .c o n sta n t vector
and a R a y l e i g h - d i s t r i b u t e d v e c t o r 9 ( p o tf e r
of R ayleigh v ecto r,
is
- 1 0 dB
re la tiv e
to th e
*
vector)
i^ p lo tted
w ith the
w ell
for com parision.
d istrib u tio n
As
for
for
the non-fading d a ta
main - r a y
(le ss
t h e o c c u r r e n c e % o f ^ery.
t h a n / 2 0 dB r e l a t i v e
to th e
normal
*
are n o te d /-
For the r e f l e c t e d
is
am plitude
•>
’
/
‘
ray,
*
the
the
during fa d in g p e r io d s ,
lo w s i g n a l l e v e l s
in
-The agreem ent betw een
th e o r e tic a l C onstant P lua-R ayleigh d i s t r i b u t i o n
dem onstrated.
value)
C onstant
'
t h e main r a y a m p l i t u d e d i s t r i b u t i o n
^
it
is
-
recalled th at
the r e s u l t s
S.
'
1#80 e x p e r i r a e f t t , i n d i e cite a l o g - n o r m a l - d i s t r i b u t i o n
d uring n o n -fad in g p e r io d s .
V
in
T h e same
d istrib u tio n
is
not
^bserved
f o r t h e 1981. e x p e r i m e n t . As f o r t h e f a d i n g d a t a ,
^
x
*■
th e g e n e ra l in c re a s e of the second r$y
am plitude
re la tiv e
to
its
n o r m a l ?v a l u e , i s n o t e d .
*
.
/
,
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
*
0.01 0.1 '
»1
5! 10,
50 .
V 90r
’ 99
Percentage of time amplitude exceeded
"*9
--
Lj _jL;
.100-
§0
'
I I 1 t-1 I 1 t__l
J
<b).
m
1 -w -
f.admg
q
%
& -20-
L.
■o • c -30o
■* ^
“tft
-1.0—
>■»
non-fading
Si
'*
/
T
TT
0.01 0.1
1
-
<,
■
y -r n—r— f— r>-----j i
MO-
«
SO
% 90
* =99
|"
99.9 99.99 >
4 •' '* c. •
*.
•
• •1
' 1. j • > Percentage f1 1im<^iinp1ttude exceeded
a
,
i
P ifg / 6.16 ' Distributions of the ray 'amplitudes*in cthe
* 1=98; e x p e r i m e n t p l o t t d d ’ o n H o m a l P r o b a b i l i t y
,
.P W f-
*1 . .
' •J *
-’
.,, * t
•■
* * **
•
\
%
*,
V •
'
•
r> ,■
c
" e■
-,1 *. •.
'
y*
hr:
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
160
,;rT
«
,
# -0
*•
6.7
.
Some
Fundy
y
*
*
LSummary
■
j
, #
of
.
,
*
\ 2
w
•
>
a'
a s p e c t s , o f m i c r o w a v e p r o p a g a t i o n a c r o s s t h e Bay
y
o *
«
\
have been exam ined w ith r e f e r e n c e to the r e s u l t s ’
o b t a iH f e d . f r o m two p r o p a g a t i o n e x p e r i m e n t s .
The p r o p a g a t i o n
j '
•e •
c h a r a c t e r i s t i c s * d uring
non-fading
periods
are,
i n most
*
_
a*»
c a s e s , w e l l e x p l a i n e d by a m o d e l o f a u n i f o r m
refractiv ity
g rad ien t.
P ropagation
cond itio n s
*
d u rin g
h i^ h ^ ^ v ariab le.
’
faA og^
periods
are
c-
The e x p e r i m e n t a l ; r e s u l t s ,
t o two major: c a u s e s o f h e a v y
J
fading
.
—
how ever, p o i n t
nam ely,
the
sea'
y
r e f l e c t i o n and a t m o s p h e r e l a y e r s .
i
'
A lthough th e r e f l e c t e d
ray is
effectiv ely
'
N orth.
M ountain
c ase d uring
the
under
/
,
ray
increased
am plitude.
>
a t N orth
T his,
in the c le a r a n c e
•
M ountain
5
and
in t h e d i r e c t r a y , can le ^ d to
*
"3
fad es in th e re c e iv e d s i g n a l .
’* •
'
experim ent,
j
, tbe
I
, i
an
severe
deep
*
»
*
time- v a l u e s o b s e r v e d d u r i n g
lay er , stren g th A
■...
2
a
the
'
extrem ely
•
From t h e maximum d e l a y
r
of
•q o n s e q u e n t l y
com bined u i t h o c c a s i o n a l
' defocussing
t
the
o f most a t m o s p h e r i c
^
i l a y e r s i l l t h e Bay o f ? u n d y was e s t i m a t e d t o
be l e s s
than'
v •
'
-3 0 .N 0 .
O n l y on" p n e
o c c a s s i o n was. a v a l u e o f p l p s e t o
• - 5 0 NO o b s e r v e d .
*
c o n d i t i o n s , such i s not the
*
The p r e s e n c e o f a l a y e r _ below
c a u s e an i n c r e a s e
reflected
by
e
normal
fading p e r io d s .
antennas w i l l
*
blocked,
-
■1-V
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
C hapter 7
THE STATISTICS OF SIGNAL FADING
7.1
In tro d u ctio n
,
4
*
?
I n t h e d e s i g n o f r e c e i v i n g e q u i p m e n t and, c o m m u n i c a t i o n
%
system s t o meet c e r t a i n
of the s t a t i s t i c s
r e lia b ility o b jectiv es,
of s ig n a l fading
is o fte n
a know ledge
requ ired.
For
a
exam ple,
the
s t a t i s t i c s o f fad e depth d i s t r i b u t i o n
an e s t i m a t e t o
b e made
allow s .
o f th e p r o b a b i l i t y o f occiwrrence
of
r
f a d e s w h ic h w i l l e x c e e d a g i v e n f a d e d e p t h s o t h a t a d e q u a t e
receiv er
fa d e m a rg in s ca n be i n c o r p o r a t e d
d esig n .'
in th e
equipm ent
-r '
•
’
■ 1
:
*From t h e p r o p a g a t i o n p o i n t o f v i e w ,
it is
inform ative
to
c o m p a r e f a d i n g s t a t i s t i c s o b s e r v e d on p r o p a g a t i o n p a t h s
'v
• w i t h d i f f e r e n t p a t h g e o m e t r y and
terrain
ch a ra c te ristic s.
C o n c lu s io n s , drawn fromd e t a i l e d p r o p a g a t i o n . s t u d i e s f o r
*
■
one
'
p a r t i c u l a r p r o p a g a t i o n p a t h may* t h e n
be
related
to
the
* *
*
fading
ch aracteristics
f a d i ri ^ i s t a t i s t i c s .
'T h e s t a t i s t i c s
the
1980
'
paths
..
w ith
4
/
sim ilar
‘
+
’
o f f a d e d e p t h d i s t r i b u t *i o• n o b t a i n e d• f o. r* r
and 1981 experim ents are p resen ted in th is
'
■
chap ter.
on
*
*
both
ofrs^rved
«■
..
\
\ ,
»* •
' . . -\ •
•
r?
(
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
y
+
*
.
♦
•
162
7 ,2
S ignal Level D is trib u tio n s
0
o
7 .2 .1
S t a t i s t i c a l M odels
•*
Th e
sig n al
•
statistics
p r o p a g a t i o n work a r e :
(a)
th at
the
number
of
fades
below
sig n al
sta tistic s,
-0
level
N(L) b e l o w a g i v e n l e v e l ' L ,
and
.9
L.
a ' given
:
*
of fades corresponding
I n ' ad d ition
t h e d i s t r i b u t i o n o f sigTial
to
to
these
lev el
V arious
describing
♦
fading
enhancem ents
'
d istrib u tio n
fu n ctio n s
are , a v a ila b le
experim ental
resu lts
d istrib u tio n .
The a p p r o p r i a t e
are
compared,
form f o r
R(V<L)
ere
V
is
•
.
-
the
a
*
= 1 - e x p (-^ i2}
•*
1
w, *•
norm alized
sig n al
am plitude
rmalized* t o
the
root-m ean -sq u are
0
;
sig n al le v e l.
£ q . (7.1) i s in f a c t a
.
(7» 1)
(usually
*
(2 .2 0 ).
As
discussed
v a l u e ) , and L i s t h e
_
n o rm a liz e d form o f
in S ection 2 .4 .3 ,
th e R ayleigh
d is tr ib u tio n "describes ttie am plitude of. a re s u lta n t
vector
is- the .sum of a larg e number, of random „interfering*
v ec to rs.. Each of these' random
v e c to rs
has ' an
am plitude
'
.
f
‘
o
■
wt)ich
w h ic h
i s g i v e n by [39]
-
which
A
is
the R ay leig h
*
®
describing
sig n al
0
Eq.
for
the s t a t i s t i c a l behaviour of fa d in g s i g n a l s .
*
i '
f u n c t i o n w h ic h i s „monunonly u s e d a s a r e f e r e n c e / w i t h
3
a
.
are a lso of i n t e r e s t .
fading
in
L,
th e average d u r a tio n jt(L )
given
in terest
lev el
_
.(c)
of,
t h e p r o b a b i l i t y P(V e ' L ) ’ t h a t t h e
n o rm alized s i g n a l a m p litu d e V i s
(b)
are
is normally d is trib u te d about £ero and-a phase which
#
"f *
"
Jn
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
*
t*
163
*
is
u n i f o r m l y d i. s t r i b u t e d
in th e
i n t »e r v a l f r o m 0 t o 2ir .
*
In
lin e-o f-sig h t
' c o n d itio n s ; for
*
'
a
«
5 sa tisfie d .,
R ayleigh
p ropagation,
d istrib u tio n
are
the
n o t alw ays
*
However,
♦
tropospheric
it
has
been ' p o in te d
out
th at
the
*
re stric tjy e
conditions
d istrib u tio n
conditions
[,21] ,
under
w hich
R ayleigh
was d e r i v e d a r e s u f f i c i e n t ; b u t ■ n o t
for
{45] .
T herefore,
»
necessary
the am plitude V to be R ayleigh d i s t r i b u t e d
n e e d ' no't b e l a r g e .
t h e number o f
in terferin g
sig n als
‘.
\
'.
I n some c a s e s t h e r e s u l t a n t s i g n a l
R ayleigh
the
component
plus
a
main
or
*
the
is
sum
of
d ire c t sig n al.
a
The
d i s t r i b u t i o n o f t h e r e s u l t a n t a m p l i t u d e f o r t h e s e c a s e s was
*
*
*
stu d ied
in
d etail
by N o r t o n e t a l .
[39] and t a b l e s o f
• *
*
v a lu e s of th e p r o b a b i l i t y d i s t r i b u t i o n of the am plitude
a
C onstant
prepared
v e c t o r p l u s a R a y l e i g h - d i s t r i b u t e d v e c t o r were
for d if f e r e n t v alu es of
R a y le ig h com ponent.
the
-
mean
po w er
i n . the
♦*
y
*
»
A nothei ~ d i s t r i b u t i o n
fu n ctio n
•»
*
*
of
*
w hich
is
found
, in
1*
literaitu re
fading
sta tistics
is
the m -D is trib u tio n
»
..
*
d e r i v e d by N^k agam i [ 2 2 ] . T h i s
is a
general
d istrib u tio n
fu n ctio n
^on
the
shape
o f w h i c h may b e v a r i e d t o f i^ t v a r i o u s '
e x p e r i m e n t a l d i s t r i b u t i o n ' s ' by
ad justing
a"
param eter
m.:^
However,
the p r a c t i c a l a p p l i c a t i o n o f t h i s f u n c t i o n i s l e s s
. I":
'
common d u e - t o i t s s o m e w h a t
motec o m p lex
fu n ctio n al
form .
*.
4
\
N everth eless,
*
it
’* i s
in terestin g
.
to
note , t h a t
the
»»
, m -D istrib u tio n includes th e R g y le ig h d is tr ib u tio n
• o n e -sid e d G edssian d i s t r i b u t i o n
and
the"
as 'p p ^ i a l c ases.
*
■
.
'
,
R eproduced w ith perm ission o f the copyright owner. Further reproduction prohibited w itho ut perm ission.
' — ’
4
'
In t h e d e s ig n
of
com m unication
system s
to
satisfy
"
r e l i a b i l i t y ' requirem ents,
the
em phasis i s o f t e n
i
certain
*
p l a c e d on t h e d e e p f a d e r e g i o n .
model
in
.w hich t h e
Based
on
fading s ig n a l V e ^
c o n sta n t u n it.v e c to r p lus a
resu ltan t
a
is
th eo retic al
composed o f a
in terferin g
v ector
t
Re 7® , s u c h t h a t
1
^
*
V e ^ = 1 + Rej ® = 1 + a + j 6
L in
[45]
shows
sta tistic s
th at,
of the fading
in
the
deep
..
(7.2 )
fade
region,
the
s i g n a l o b e y t h e po w er l a w s o f
deep
fades:
P(V < L )
oc L 2
(7.3)
^
N(L)
<*■ L
t (L)
oc L .
f o r sm all ^
widec l a s s
/eith er
\
, ^
t o be a p p l i c a b l e '
’
appear
dependent
or
independent;
d istrib u ted ;
or non-G aussian.
and
a
0
and
•
re su lta n t of a ll
the e x tra n e o u s s ig n a l s ,
■ 7
.
*
The p o w e r laws'^ i n E q s .
th at
uniform ly
is.
a
a
3
or
3 e i t h e r G aussian
•K
.
The o n l y r e q u i r e m e n t s t a t e d
in terferin g
v ector
be d e s c r i b e d
by
*
"
■
.
d e n s ity , fu n ctio n
f ( a , B)
and * t h a t
provided
to
o f fa d in g problem s w i t h . t h e v a r i a b l e s R and
non -u n ifo fm ly
rays.
(7.4)
(7.5)
k ,
,
T h e abtSve r e l a t i o n s h i p s
♦
■*
is
t h a t <the
a jo in t p ro b ab ility
' *
it
represents
the
n o ise, echoes,
(7.3) to (7.5)
and
‘ ; .
. •*
w i l l then hold
sm o o th - v f u n c t i o n , w h i c h i s
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
\
*
' •
■
165
*
, neith er
'
' U
1
s i n g u l a r ’ nor
zero
at
th e
deep
fade
point
= - 1 * B* 0 ) .
F urtherm ore,
*
singular*
at
L in • 'a ls o
shows
re la tio n sh ip s,
s m a ll L, becomes
th at
if
f ( a ,3 )
is
»
9
■
*
«
( f* = - 1 , 3 =
for
P (V < L)
0),
the
co rresponding
(7.6)
« L 2"y
•
'
>
I
i
> \x > h
From E q .
*
of
,
(7 .8)
l
( 7 . 6 ) j . t is* s^een t h a t ,
deep
. Ifw
oc
for
y
< 1, the p r o b a b ility
f a d e s d e c re a s e s a t a slo w er
r e l a t i o n s h i p in Eq.
A
(7.7)
*
•
t (L)
^
(7 .p .
rate
than the
square
The s e t o f e q u a t i o n s
(7.6*)
*.
to
(7 .8)
t h u s d e s c f i b e s f a d i n g c o n d i t i o n s w h i c h a r e m ore
s e v e r e th a n th o s e w hich obey E q s .
severe
\
to
(7*5).
f a d i n g c o r r e s p o n d s t o t h e c a s e when
is
s a id to
a
stro n g w a te r-re fle e te d
- of
(7.3)
the
apply to c e r t a i n
over-w ater
y =h
rad io
The m ost .
and t h i s
^ i n k s on w h i c h
ray e x i s t as a dom inant component
in terferin g -v ecto r.
•
»
%0
*
For
ra d io path
■*f
C onsultative
0
‘
R esigns,
i
“C o m m i t t e e
In te rn atio n al
proposed
, *
a
for
the o v e r a l l p r o b a b i l i t y o f f a d i n g , P ( V < L ) ,
••
'
♦ -»
fades,
(fade 'd e p th s
e x c e e d in g * a b o u t / 1 5 'd B ).
for
^
E stim atin g
4
* deep
e m p iric a l form ula fo r
the w o rst/fa d in g
. *
^
.
‘
•
.
•
where
.
R adio
form ula
1*
(CCIR)
the
♦
■
■
P(VCL)
*
“■
K
•
and
= K, Q . L 2 . ' f B . d C'
■
•
'
’
■
Q are
facto rs
for
m o n t h is^ ( 4 6 ] ,
-
• .
■
*
•
The
[47]
►’
(>.9)
'
clim atic
.
•
. • ,
..
.an d / te r r a in
■ *
*
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
.
co n d itio n s,
d is
the path
i n GHz,
a n d B and C
v alues
of
are
len g th
em p irical
1 . 0 a n d S'.O f o r
and Q a r e a l s o
tab u lated
co n d itio n s.
i n km, f i s
the
co n stan ts
frequency
w hich
the U nited S t a t e s .
have
V alues of K
f o r variouS^ c l i m a t i c
and
terrain
V
J
*
o
*
7 .2 .2
'
»
6 -
P rev io u s E xperim ental F in d in g s ,
The a v a i l a b l e e x p e r i m e n t a l e v i d e n c e
the
in
s q u a r e ^aw r e l a t i o n s h i p f o r
a
the deep fad e r e g io n .
B abler
6 GHz
for
path
in
an
appears
th e am plitude d i s t r i b u t i o n
[48]
presen ted
e x p e rim e n t p erfo rm ed on a 42.5
A tlan ta
w hich
w ell
to su p p o rt
support
the
resu lts
km o v e r - l a n d s
square
r e l a t i o n s h i p . • O t h e r s t u d i e s c o n d u c t e d by B a r n e t t
V igants
[50]
a t 4,, 6 ,
and 11 GHz
a
on
at
45-. 9 km
law
[49]
a nd
over-land
i
»
p ath a lso produced , r e s u l t s
jj/hich a r e i n a c c o r d a n c e withK t h e
.
*
*
(7 .3 ), (7 .4 ),
and
(7 .5 ).'
In ,
*
*
r e s u l t s a lso su p p o rt a lin e a r frequency
V
r e l a t i o n s h i p s g iv e n in E qs.
a d d itio n ,'B a r n e tt's
dependence of
It
is
noted
d istrib u tio n ,
t h e f a d e "depth d i s t r i b u t i o n JL&ee
conducted
in
the
f d 3 d e p e n d e n c e @f t h e f a d e , d e p t h
t
where f i s t h e f r e q u e n c y and d
is
the p a th
j
r e s u l t s were r e p o r t e d f o r
D enm ark
'*f
of
*
[51].
a 14 GHz
experim ent
by S t e p h a n s e n a nd M o g e n s e n
a l s o p r e s e n t e d one o f
d istrib u tio n s
(7 .9 )).
th at
l e n g t h , w as o r i g i n a l l y d e r i v e d b y R u t h r o f f
S im ilar
Eq.
t h e f ew a v a i l a b l e
*
.
sig n al
enhancem ents
[52]
who
sets, , o f
em p irical
*
w hich^. f o l l o w
the
I*
✓
r e l a t i o n s h i p P ( V > L ) « L ~ Hm 5 .
-
w
•
»
*
*
*
*
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
f
■
167
7 .3
Experim ental R esults on Fade Depth D is trib u tio n s
(D
7 .3 .1
G eneral D escrip tio n s
The p r o p a g a t i o n e x p e r i m e n t s p e r f o r m e d a c r o s s
♦
of
Fundy
t h e * Bay
»
wer e
not
configured
for
the
stu d y of fading
sta tistic s.
O n l y o ne sw ee p r e c o r d was t a k e n
every
10 s .
k
t '
S tatistics
on- t h e number
and d u r a t i o n o f f a d e s w e r e not.
generated sin ce
10 s .
most f a d e s ’
N ev erth e^ss,
have
sta tistic s
d u ratio n s’ of
less
than
on f a d e d e p t h d i s t r i b u t i o n
m a y «b e g e n e r a t e d ’and c o m p a r e d w i t h t h e o r e t i c a l p r e d i c t i o n s * ,
- a ss u m in g
th at
t h e 10 s s a m p l i n g
in terv al
o nly has the
e f f e c t o f r e d u c in g th e sample s i z e . ,
«
.The p r o b a b i l i t y d i s t r i b u t i o n o f f a d e
depth,
P(V <L ),
fl
was
generated
by d i v i d i n g t h e t o t f c l n u m b e r o f d a t a p o i n t s
r~
o f l e ^ e l V < L by t h e , t o | i a l
sample s i z e .
for ^ b o th
experim ents
using
frequency
( 9 , 5 GHz) o f
each
averaging
t e c h n i q u e may b e
T h i s was p e r f o r m # !
th e s i g n a l l e v e l a t th e base
*
sweep r e c o r d .
'A lth o u g h
an
employed t o i n c l u d e a l l d a t a
*
was
decided
f
,
d i f f e r e n t fre q u e n c ie s w ith in the
th at
such
sweeps,^
a t e c h n i q u e may c r e a t e
(
reference
I
it
u n d esirab le side e f fe c ts
4
. d ue t o f r e q u e n c y d e p e n d e n t f a c t o r s
t
at
.
»
sig n al
w ith in sweeps. *In
levels
for
any . e v e n t ,
and d i f f e r e n c e s
d ifferen t
the
in
frequency
r e s u l t s - do
the
step s
seen)
to
d a ta base in u s in g . o n l y th e d a t a
at
\
in d icate,
an
adequate
the base f r e q u e n c y ,' a t
l e a s t f o r *tfce 198*1 e x p e r i m e n t
provides data for a 35-day period-.
*
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
which
Due t o
y
less
t h a n i d e a l e q u i p m e n t a l i g n m e n t i n t h e 1980
experim ent,
r e l i a b l e r e s u l t s were o b t a i n e d o n l y f o r s i g n a l
' ■
.
k lev els
f r o m 10 dB down
to
ap p ro x im ately
- 3 0 dB
(both
* /
—
*•
*
*
*
.
-relativ e
to
-l
experim ent*
*
normal
produced* . r e l i a b l e
1 i
• r ef l a t i v e
;s i g n a l
—
l e y e l ) ’.
,
v
i m p r o v e m e n t s made t oft
«
•
the
resu lts
the
In
/
»
the
1981
’4
receiving
equipm ent ,
\
from
10 dB
down , t o . - 3 6 dB
*’
...
'
>
to th e normal l e v e l .
*,
I n com puting th e s ig n a l , l e v e l d i s t r i b u t i o n s , f o r
both
’ Jt-'
experim ents,
the
r e f e r e n c e . 0 dB l e v e l
used
in* each
,
*
*
experim ent are
d ata
- ,
bases.
•
»
i
s.
th e m edian s i g n a l l e v e l s f o r th e ' r e s p e c t i v e
, , v
■
■*
F urtherm ore,
s i g n a l lev.ei d i s t r i b u t i o n s f o r
the non-fading d a ta ,
*■
<
;
the fa d in g
d a t a , , and t h e c o m p l e t e d a t a ”
'
♦
b a s e s ; w er e c o m p u t e d f o r e a c h e x p e r i m e n t .
•
•
’ -
,
f 9
•
«
7 .3 .2
S ig n a l Fading S t a t i s t i c s -
J
The s i g n a l l e v e l d i s t r i b u t i o n s
*
shown
in
F ig.
1
7.1
for
^
i
9
com plete d a ta b a s e s .
^
the'
•
'
t h e ' 1980
i
data
n o n -fad in g ,fa d in g ,
9
A reg ressio n
W
,
■
for
.
•
t e c h n i q u e Was
and
are
the
used
• to
f i t - the
resu lts
for
fade
d e p t h s e x c e e d i n g 1$ dB. The
>
'
r e s u l t s i n d i c a t e a s q u a r e law r e l a t i o n s h i p
for
both
the
•. *
9
, /
f adi
d ata
and
t h e e n t i r e d a t a base,, c o r r e s p o n d i n g t o a
«
•
,
f
•
¥
v a lq e of
y ■ 1 in E^. ( 7 . 6 ) .
’*
1 •
u
■
A lso p l o t t e d in F ig . 7 .1
k
*
’
'
is
the p r e d ic te d d i s t r i b u t i o n
*
-
'
for
Eq.
CCIR
t h e w o r s t f a d i n g mo.nth u s i n g
(7 .9 ).
t h e CClR
fo rm u la g iv e n in
p
In com paring th e e x p e r im e n ta l - r e s u l t s w ith
p red ictio n ,
a few p o i n t s
V
are n o ted .
•
■
w orst
,
*
*
t h e 198 0
1
experim ent d id not corresp o n d to the
V
F irst,
the
fading
m onth.
)
«
s
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
*
•
'
\
F ig,
’
-
o
'
10
Fade depth,
,
20,
-2 Q lo g 10L
7..1 F a d e d e p t h d i s t r i b u t i o n s f o r t h e n o n - f a d i n g
~ dtfta, f a d i n g d a t a , and th e t o t a l d a ta b a se s
i n t h e 1 9 8 0 e x p e r i m e n t . *• *
N
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
170
*
Second,
the
data
base for
days-of data sele c te d
extended p e rio d .
n^fe
th e ex p erim en t c o n s i s t s o f ten
over
an
The e m p i r i c a l r e l a t i o n s h i p d e s c r i b i n g
the
fa d e depth d i s t r i b u t i o n
4
com pletely
for
random
t h e 1980 r e s u l t s
a
r
*
at
is
*
P(V < L) = 0 . 1 4 L 2 ,0
f o r L < 0.18
(7.10)
t
I
The s i g n a l l e v e l d i s t r i b u t i o n s
f o r , t h e 1981 e x p e r i m e n t
9
are
shown
r( f o r
in
F ig.
7.2.
T h e CCIR p r e d i c t e d d i s t r i b u t i o n
th e O t t e r Lake - N ic ta u x S outh p a th )
is a lso
included
(
for *com parision.
The
most
im portant
P(V < L) ^ L 1 ’ 6 r e l a t i o n s h i p was o b t a i n e d
fit
for
resu lts
less
than
resu lt
T his
co rre sp o n d s to a v alue of
fact
th at
the l i m i t o f
attrib u ted
M ountain.
fading
to
the
A lthough
—
y » 0.5
p a rtia l
the
- 1 5 dB)
instead
of
1980
y = Q.8- ir^/^^[.
m echanism
the
resu lts.
(7 .6 ).
is not a tta in e d
*
blockage ^-offered
fading
th at a
(using a r e g re s s io n
P(V < L) a L 2 *° r e l a t i o n s h i p o b t a i n e d f o r . t h e
m
is
is
p artly
by
during
The
N orth
severe
nam ely t h e ' d e f o c u s s i n g e f f e c t o f th e d i r e c t ray
arid t h e i n c r e a s e d C l e a r a n c e
of
the r e f le c te d
the
resu lts.
ray,
(and th u s
increased
am plitude)
s h o u l d be k e p t i n mind when s t u d y i n g
0
4
*
^
*
propagation
path
is
"
i n t h e w o r s t m o n th
v el.
for
s e e n t o b e t o o o p t i m i s t i c by a
f a c t o r o f 2 . 5 a t t h e 30 dB f a d e l e v e l a n d 3 . 6 . a t t h e
vl e
* .
,
V *
T h e CCIR p r e d i c t i o n . f o r f a d i n g
^
th is
*
'
4|0 dB
t
*
•;
.
The
em p irical
relatio n sh ip
for
the
fade
depth
d is trib u tio n ^ on the O tte r Lake - N ictaux South path fo r the
*
M
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
m
} 1981
#*
fading, P « L
Q.
9
total
XJ.
-
P a l.'-6
non-fading
CCIR
•10
\ Fade depth,
i
-20 log1QL
**
(dB)
1
?
Fig.
7.2
F a d e depth* d i s t r i b u t i o n s f p r t h e n o n - f a d i n g
d a t a , , f a d in g ^ d a ta , and th e t o t a l d a t a b a se s
i n t h e 19 81 e x p e r i m e n t s .
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
7 .3 .3
S ig n a l Enhancement S t a t i s t i c s
.
•
p.
The
m edian
•
'
sta tistic s
lev el
are
I .
.
enhancem ents
above _the
.
’
’
^
summarized in F i g s . 7.3 a n d . 7 .4 f o r th e *
.
t
f
f
‘
*
*,
c
^
e*
'
V.'
f •
y
‘
allow
c o m p a r i s o n " ’ w i t h t h e S t e p h a n s e A and M o g en sen r e s u l t s ,
**
’
*
«
,
' # '
the e m p iric a l r e l a t i o n s h i p s fo r s i g n a l enhancement
(fitted
' .•
.
"
u s in g a r e g r e s s i o n t e c h n i q u e ) wete cb m p u ted . T h e s e ® r e :
4
" . '
(1) A y l e s f o r d - O t t e r L a k e , 1980
* ©
" "
P.(V > L ) = 0 . ^ 4 L- 7 *8
I o-
‘
I '
* • J,
,
-5 ’
"
*
1.2 5 < L < 2.8
*
-*•
1 # '. , -
•
-r-{7 .1 2 )
*'
(2) O t t e r L a k e - N i c h a u x * S o u t h , . 1981
*
P (tf*L )
*
= 0 . 6 5 L7 3 * 9
*
»
-
‘
*
,
*
..
[52]
* w <^ •i *•
P ' ( V > lV -
1.25. < L < 2 . 8 '
.V.
• <7-13.)
v
C 3 ) S t e p h a n s e n and .M og ensen
0
4
*
*
9
..
~
. fo r '-sig n a l
4
r
“ .
u
\
' *
'
1
198 0 and 1981 r e s u l t s r e s p e c t i v e l y .
&l)so p l o t t e d
are
t h e 11
^
^
‘•
enhancement
sta tistics
given
by S t e o h a n s e r i a nd M o g en sen
'
•
. *
• *"
[ 5 2 J for: an o v e r - l a n d p a t h a t a f r e q u e n c y o f
14 GHz.
To
^
.
* '
v
<
.
.
"
*
i
-*
0 . 0 5 9 L-1**5
-
*
l ^ V O ^
.
3.*©
t•
( 7 ’. 1 4 )
w
7 "
■ ’
7 ,
^
7
' - y
T h e raufchr h i g h e r p r o b a b i l i t y o f s i g n a l e n h a n c e m e n t s
in
7
the
198 1
e x p e r i m e n t c o m p a r e d w i t h t h e S t e p h * n s e n a nd M o g en sen
' 5
-V
' . . : '■
r e s u l t s ' i s t h o u g h t t o B ^ / a u e t o m o r e 4* f r e q u J w t o c c u r r f e n d e s ’
■
"‘ of
atm ospheric . l a y e r s
of
in
t h e . . Bay
of
freq u en t occurrences o f m u ltip ath propag atio n
.' *
*
°
•
. •’ ‘ , 1
*.
a•
'r
’
** -*
m*
•>
Fundy.
'
T h e m ore *
th e n l e a d
■« '
* u<
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
*
j
. *
Jto
■'
OF/DE
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Y980
fading
-c
P « L"®*1
to ta l
Poe L 7*8
/
F ig .. 7 .3
6
10
• Enhancem ent, 20 log10L
k
2
0
.
1dB)
D i s t r i b u t i o n s o f ''s i g n a l enhancement
f o r t h e 1980 e x p e r i m e n t .
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
"^T
i9 ai
<u
£
<1)
to ta l '
r
<U
>
P<tL-3*9
|'1 0 '2
o
c
o
jC
c
<D
e
r
S tp p h a n se n
■8. M ogensen
10-3
Pa
•c
'S '
- o.
o(_
Ll
.10 ■4 __
/
1
10
1
i.
1
8
6 .
U
1
2
Enhancem ent,, 20 lo g ^ C .
F ig.
7.4
- 0
(dB)
d i s t r i b u t i o n s o f s ig n a l enhancement ap r
• th e 1981 e x p e r i m e n t .
%
’ t
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
a h i g h e r p r o b a b i l i t y o f signal-^-enhancem eiits,
'
. .
.
7 .3 .4
O ther A sp ects
.
It
is
.
in fo rm ativ e
1
to
plot_
-She
sig n al
lev el
*
on. R ayleigh P r o b a b ility C o o rd in a te s so t n a t
,
d istrib u tio n s
' <*
•
c o m p a r i s o n s may
be
d istrib u tio n .
The
..
made
w ith
■ .
the,
th eo retic al
R ayleigh
*
®
presen ted
resu lts
for
b oth
are'
in F ig .
7 .5 .
A lso, p l o t t e d
i n t h e .same f i g u r e
are
th e t h e o r e t i c a l R ayleigh d i s t r i b u t i o n
and t n e C o n s t a n t P i u s
R ayleigh d i s t r i b u t i o n
R ayleigh
V ector
(power
i s - 6 - dB r e l a t i v e
\
*
in
tne
t o ^ € n e C o n s t a n t «v e c t o r ) .
a p p e a r t o be in
good
9
the
C onstant
in terestin g
P lus
point
R ayleigh
noted
is
for
th e
•
d istrib u tio n .
th at
t h e 19 8 0 r e s u l t s
a l.\
^
E nglish
C hannel.
*
'
agreem ent
the
’ , A nother
shape
of
.
the
*
is very s im ila r
(53] f o r
w ith
*
9
. p r e s e n t e d by A l b r e c h t e t
o
T h e t1 9 8 0
. *.
1
d istrib u tio n
d istrib u ted
1
experim ental r e s u lts
r
experim ents
V
to th a t
a n 88 km p a t h a c r o s s
The p r o p a g a t i o n p a t h f o r
th e
5 GHz
%
'
e x p e rim e n t a c r o s s tn e E n g l i s h C h an n el i s a l s o open
to
sea
•
*
*
#
%
V"
r e f l e c t i o n ' \ a d d c o m p a r a b l e a n t e n n a e l e v a t i o n s a b o v e t h e s e a *r\
4
s u r f a c e were u s e d .
*
Wnile* t h e d i s t r i b u t i o n s
-
appro x im ated
for
*
t h e . 19 8 0 r e s u l t s
are
w ell
*
b^ a C o n stan t P lu s R ayleigh d i s t r i b u t i o n ,
th e
r e s u l t s f o r ’t h e / 1 9 8 1 e x p e r i m e n t i n d i c a t e d f a d i n g c o n d i t i o n s
th at
/
a r e ^ moj/e
severe /th a n
R ayleigh
o b s e r v a t i o n s Were, a l s o r e p o r t e d by
fad in g .
Gudiftandsen
and
S im ilar
L a r ’s e n
*
15 4 J
for
tw o o v e r s e a p a t h s
i n Denmark.
*
atm ospheric-J% yers as c o n tr o llin g
facto rs
T n e . im portance o f
in s ig n a l
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
fading
Reproduced with permission of the copyright owner. Further reproduction
T -C in rrp -r-i
f
10
C0
S - 10
C o n s ta n t
p lu s
R ayleigh *
a
>
o>
|
-20
cn
't/i
Rayleigh
prohibited without perm ission.
I I jJ 1. 1 1 Li i - i.
01 1
10
'5 0
P ercen tag e of tim e
90
sig n al
99
level
5 9 .0
9 9 .9 9
.
exceeded
R ayleigh v e c to r is - 6 d B in power relativ e to c o n s ta n t v ecto r.
F ig.
7 .5
S ig n al le v e l d is tr ib u tio n s fo r th e
p l o t t e d on R a y le ig h C o o r d i n a t e s .
1980 a n d 1981 . e x p e r i m e n t s
t 76
'
I 77
is
p artly
severe
dem onstrated
in
t h e 19 81 r e s u l t s
fading
was o b s e r v e d
even
C
T
blockage to th e r e f l e c t e d ra y . -
w ith
\
i n t h a t more
b etter
terrain
'
* *-
4
♦
I
Summary
{•
7.4
' The
sta tistic s
enhancement
of
fade
d istrib u tio n
depth
d istrib u tio n
and
f'
b e e n p r e s e n t e d f o r t h e two
have
p r o p a g a t i o n e x p e r i m e n t s p e r f o r m e d a c / o s s t h e Bay o f
The
d istrib u tio n s
1
p r e d i c t i o n s and a l s o
.
we re ,
compared
w ith
th eo retic al
*
ex istin g
experim ental
resu lts
w ith
\
’
a v a i l a b l e* i n t h e
resu lts
f
literatu re.
S ig n ifican t
r
d ifferen ces
obtained
-were
P(V <L )a L 2
relatio n sh ip
w hile
d ifferen ces
is
fP{V 3 L) * L 1 ’ 6
are a t t r i b u t e d
ch aracteristics
«
as w ell as
ex p erim en t being perform ed
may
be s a id f o r
4,
•
f ro m t h e two e x p e r i m e n t s .
/
resu lts
4
observed
«
a
was
to
betw een'
In p a r t i c u l a r ,
a p p lic a b le ‘ to
of
19 80
obtained for
1981. . The
in
seasonal v a ria tio n s
th e fading
the
path
— t h e 1981
season.
The
same
t h e en h an cem en t r e s u l t s which a r e com pared
i
sig n al
the
/
the d iffe re n c e d
in
the
ft
*
w i t h t h o s e o b t a i n e d by S t e p h a n s e n and M o g e n s e n .
i
FUndy.
The amount
>
enhancement
su b sta n tia lly larg er
o b s e r v e d i n t h e 1981 e x p e r i m e n t i s
*
th a n t h a t r e p o r t e d in t h e l i t e r a t u r e .
Th e o v e r a l l s i g n a l l e v e l d i s t r i b u t i o n
for
1980 i s w e l l
a p p ro x im a te d -by a C o n s t a n t P l u s R ayleigh" d i s t r i b u t i o n .
t h e 1981 r e s u l t s ,
t h e f a d i n g o b s e r v e d i s m ore
severe
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
For
than
178
R ayleigh
fading
d esp ite
more
effectiv e
te rra in
u n d e r, norm al cond i t i o n s .
I
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
blockage
*
Chap t e r 8
.
THE DIGITAL RADIO
8 .1
In tro d u ctio n
*
' M icrow ave d i g i t a l r a d i o
system s
dre^ r a p i d l y
rep lacin g
i
conventional
analog
ra d io system s in s h o r t- h a u l
telephone
<?
tran sm issio n a p p lic a tio n s .
T y p i c a l w ideband d i g i t a l
rad io
system s
o c c u p y b a n d w i c & h s d f 30 MHz' ( i n t h e u n i t e d S t a t e s )
*
*
an d 40* MHz. ( i n C a n a d a ) .
B ecause o f t h e w ide b a n d w id th
a nd
the
m odulation
tra n sm issio n ,
d isto rtio n
fadirig.
d ig ital
techniques
these
ra d io system s
effects
caused
'
New a p p r o a c h e s t o
rad io lin k s
is
given
d isto rtio n
effects
S e c tio n .8 .3
in
the d esig n of
are
radio
in
v u ln erab le
to
the
s e le c tiv e m u ltip ath
rad io
b asic s
S e c tio n 8 .2
as
w ith
m u ltip ath
rad io in s ta lle d
t h e 1981 e x p e r i m e n t
to
the
p aths
for
found• in
the
req u ired .
a s s o c ia te d w ith
relatio n
bandw idth e f f i c i e n t
*
The p e r f o r m a n c e o f a d i g i t a l
o f Fundy d u r i n g
are
by f r e q u e n c y
th erefo re
A review o f d i g i t a l
lite ra tu re
req u ired fo r
is
then
em phasis
on
'p ro p a g a tio n .
across
t h e B ay
exam ined
r e s u lts o b tain ed
pro pagation, ex p erim en ts.
179
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
in
from t h e
^8.2
*
'
,8.‘2 . 1
_ V
‘
Background
Due t o
d ig ital
the
in fo rm ation ,
d ig ital
are
lin e-of-s;L ght
allow ,
em ploying
for^ easy
system s
d .ig ital
_
rad io s o ffe r
in terfacin g
used
of
ap p Jy icatio n s
d ig ital
and t e r m i n a l equipflw it*.
com m unication
tra n sfer
w idespread
In a d d itio n ,
'
<=r
th e
system s
fin d in g
and
sw itch in g
dem an d „ fOr
rad io
teleco m m u n icatio n s.»
econom ic a d v a n ta g e s
V
’.
increasing
•
in
*
, .
m o d u latio n te c h n iq u e s
L*
j.
M icro w a v e'D ig ital Radio Systems
.to
In
te rre stria l
in
telephone
9
|
tran sm issio n
d ig ital
o v erb u ild
ap p licatio n s,
radio
equipm ent
them o n t o
the p red o m in an t tre n d is to use
•
*
on
new r a d i o
ro u tes,
and
to
th e e x is tin g
The c o m p le x ity o f d i g i t a l
d etailed
In stead ,
d escrip tio n
to
re le v a n t asp ects
d iscu ssed
so
th at
the
analog, s y s te m .
rad io
be
system s
in clu d ed
of
d ig ital
in
th is
radio
perform ange
of
p ro h ib its
a
th esis.
system s
th e d i g i t a l
are
rad io
i n s t a l l e d a c r o s s t h e ‘B a y o f F u n d y may b e
exam ined .in
*
ft..
t
l i g h t o f th e r e s u l t s from th e p r o p a g a t i o n e x p e r i m e n t s .
The
*,’ *
p e r f o r m a n c e o f 4a d i g i t a l
-
.
.
*»
to
sta tistic a l
b its
t
is
m easured in term s o f the p r o b a b i l i t y o f e r r o r p(e)
saf
'
*
*
in t h e d i g i t a l o u t p u t .
T his
P(e)
term ,
som etim es
also
referred
f
tr a n s m is s io n system
u su ally
'
'*
the
as
the
* 'B itrE rro r-R a te
average of
in e r r o r
to
the
*
*
th e r a t i o
pf
(B B R ), . r e p r e s e n t s
th e average
a v e r a g e number o f
a s u f f i c i e n t l y long m easurem ent i n t e r v a l
'
r
*
u s e d g a t i n g p e r i o d i s 300* ms [ 2 9 ] , [ 3 4 ] .
**
.
, '
•
'»
* *
.
..
%
'
number
tran sm itted b its
a
■
of
in
[34].
At c o m m o n l y
1
An o u t a g e t h e n ijs
f ''
•
'
•
f
* ,
R e p ro d u c e d with p e rm issio n o f th e co p y rig h t o w n er. F u rth e r re p ro d u c tio n p ro h ib ite d w ith o u t p e rm iss io n .
'
,
181
<
s a i d t o h a v e o c c u r r e d on t h e r a d i o
system
*
, * •
o'
’ f o r a p e r i o d o f t i m e l o n g e r t h a n 300 m s .
'
Ityo d tlle f c r i t e r i a ' w hich
arp
o ften
literatu re
^he
when
B E R > 1 0 -lt
*
, •
*
quoted
fo r d e s c rib in g system perform ance a re
outage • p r o b a b ility ,
w hich
is
»
in
the
[29]:
(a)
the
.
^
p ro b ab ility
of
*
th e e f f e c t i v e system
o c c u r r e n c e o f a s y s t e m o u t a g e , a n d (b)
s
. f a d e m a rg in , d e f i n e d as th e fad e d e p th 'w h ic h has
the
same
p r o b a b i l i t y a s the ob serv ed outage p r o b a b i l i t y .
*\
V arious
d ig ital
*
m odulation . te c h n iq u e s
rad io system s,
(AM) t e c h n i q u e s ,
*
'
1
M odulation
.
(QAk)
(FSK);
(P SK );
(FM) t e c h n i q u e s ,
e .g .
(PM)
tech n iq u es,
e.g .
>
an d,'
■
*
A
. various
com parison
is
choice of the
req u ired
of
in
sp ectral
tS h i f t
and
Phase
[55].
m odulation
Ir^m ost cases
technique • ia ^ d ic ta te d
efficien cy
_
Phase
e
’ th es^
g ettin g
m odulation
i
sig n allin g
found
Frequency
h
A m plitude
, techniques
P a rtia l
.
(4) H y b r i d AM/PM t e c h n i q u e s , we>.g..
* »•
"
S h i f t K e y i n g (APK) .
thorough
Q uadrature.
*
Phase M odulation
, K eying
in
%
(QPR);
(2) F r e q u e n c y M o d u la t i o n
(3)
e.g . ,
Q uadrature
)
S h i f t Keying
used
r
and
•
Response
*
being
th ese include:
(1) A m p l i t u d e M o d u l a t i o n
A m plitude
are
w hich
is
by
m easured
the
the
by‘the
»
speed p e r u n i t R F;bandw idth
(in b its /s /H z ^ .
To
im prove th e s p e c t r a l , e f f i c i e n c y , most h i g h c a p a c i t y d i g i t a l
*
"j * .*’
radio, system s use m u l t i - l e v e l j s i g n a l s
in stead
of
binary
sig n als,
*
thus * g w in g
rise
to
m u lti-lev el
m odulation
*
*
*
.
•
,
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
.
•
*
schemes.<
I n a M -ary
(M -level)
tran sm issio n
system ,
each
?
tran sm itted
symbol
rep resen ts
n, i n f o r m a t i o n b i t s , w h e r e
►
n = l o g 2M. „ A t y p i c a l
exam ple
is
8-ary
PSK w h i c h
is
*
- .
commonly
.
em ployed
in
d ig ital
radio
system s u sed in th e
U nited S t a t e s .
D i g i t a l r a d i o system s
techn iqu es
are
em ploying
u s u a l l y ,c o m p a r e d by t h e i r
v e rsu s the c a r r i e r - to - n o i s e
A dditive
d ifferen t
W hite
(C/N)
G aussian N o ise.
ra tio
T his
m odulation
P(e)
perform ance
under c o n d itio n s of
is
s hown i n F i g .
8 .1
f o r v a r i o u s c om m only u s e d m o d u l a t i o n t e c h n i q u e s .
*
8 .2 .2
P r o p a g a t i o n I m p a ir m e n ts on D i g i t a l
R adio S ystem s
*
is
The m ajor
im p a irm e n t i n wideband d i g i t a l r a d i o
in-band
d isto rtio n
w hich
d isto rtio n
(due' t o an i n - b a n d
slop e)
a nd d e l a y
*
d isto rtio n
is
to
qnd
inter-sy m b o l
(C/N)
for
in th e P(e)
p resen ted
F ig .,8 .2 .
by
Lungren
The
term
The
of
.
a nd
„ »
of
P(e)
have been r e p o r te d
R esu lts of
and • Rummler
in-band
perform ance.
b a n d w i d t h , 8-PSK
P(e)
d ig ital
[56]
are
"in-band s e l e c t i v i t y "
d e fin e d -a s th e d iffe re n c e
; atten u atio n
am plitude
lab o rato ry sim u latio n s
[35] ,1561 , { 5 7 ] ...
a 30 MHz
or
in terferen ce"
d e g r a d a t i o n c a u s e d fctf i n - b a n d d i s t o r t i o n
in t h e l i t e r a t u r e
am plitude
effect
•
"cause
t? o t h
am plitude n u ll
d i s t o r t i o n . The
consequently a d eg rad atio n
Com puter
in clu d es
system s
b e t w e e n t h e maximum
versus
ra d io as
shown
in F ig .
a nd
8 .2
in
is
minimum
p r e s e n t in th£ tra n s m is s io n c h a n n e l b andw idth.
asym ptotic
behaviour
for
large
(C/N)
values
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
are
I
183
• •
P(e)
»
to
s
10* *
BPSK
10 “ *
,4-PSK
I (QAM)
8-PSK \
16-PSK
Class I •
QPR \
l-APK
r*
10 - ’
F i g . '*8.1
r
C/N (dB)
P ( e ) p e r f o r m a n c e o f M - a r y PSK, QAM", QPR, a n d
M - a r y APK c o h e r e n t s y s t e ^ a s .
The rms C/N i s
s p e c ifie d in the d o u b le -s id e * N y q u is t
bandw idth
[ 3 4 ]*
■' J
R e p ro d u c e d w ith p e rm is s io n o f th e co p y rig h t o w n er. F u rth e r re p ro d u c tio n p ro h ib ite d w ith o u t p e rm iss io n .
■
184
\
IN-BAND
SELECTIVITY, OB
(.7
5.7
-*
NOTCH
DEPTH, b db
7.7
S.S
■X'
5.5
3.7
4.4
3.5
10-4 —
2.2
2.7
m
cm IN DECIBELS
t
F ig.
8 . 2
H i g h - s p e e d d i g i t a l ra~dio I F
d is p e r s iv e fade s im u la tio n s ,
t
=
6 . 3
n s , f .= . - 1 9 . 8 MHz
r e l a t iv e to t n e ' c e n tre o f the
'c h a n n e l where f
i s th e frequency
a t th e notch
[ 5 6 ] ,
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
p a rtic u la r
occurs,
in tere stin g '
in
th at
when
i n - b a n dj */ ddiiss t o r t i o n
even a l a r g e i n c r e a s e in th e t r a n s m i t t e d power w i l l
/
not sig n ifican tly
that** of
»
.
im prove t h e P(e) performanfl^e^
E x p erim en tal evidence
suggest
_
and
com puter
sim u latio n s'
also
t h e two t y p e s o f i n - b a n d d i s t o r t i o n ,
the
t
p e r f o r m a n c e d e g r a d a t i o n c a u s e d by a m p l i t u d e s l o p e
is
much
m o re s e v e r e t h ^ f ^ t h a t c a u s e d by th'e d e l a y s l o p e [ 5 7 ] / [ 5 8 ] ,
<
[59].
In-band am plitude d i s t o r t i o n th e r e f o r e is
a useful
param eter
for
ra d io system s
th e outage p r o b a b i li t y of d i g i t a l
[60] .
^
*
i
At l e a s t t h r e e m odels have been p ro p o se d f o r m o d e llin g
-»
-o/
•*
>
■
behaviour
o f the tra n s m is s io n channel fo r th e p u rpose
the
f
estim atin g
.
*
-
o f e v a l u a t i n g a nd s i m u l a t i n g
the
perform ance
*
*
r a d i o s y s te m s undey m u l t i p a t h c o n d i t i o n s .
I ~
G reenstein
determ ine
, the
[ 3 5 1 , [51]
frequency
used a
t^ansf ^
power
series
are
effects. _
required
for
,
series
model
to
fu n ctio n of a m u ltip ath
fadirfg c h a n n e l and c o n c lu d e d t h a t o n l y
power
o f + d ig ital
tw o
term s
qf
the
c h a ra c te riz in g m u ltip ath
£
Ramadan
[58]
used-
a
two
ray
ah aly tic
'm o d e l
to
r e p re s e n t the tra n sm iss io n ch an n el.
Of p a r t i c u l a r i n t e r e s t
>
•
i s t h a t , b a s e d on t h e ' t w o r a y m o d e l , Ramadan c o n c l u d e d t h a t
t
.
-
t h e %r e l a t i v e
delay o f
th e a d d itio n a l ray
m u ltip a th d e c r e a s e s e x p o n e n t i a l l y w ith th e
(or echo)
during
e c h o \ am plitude
and
therefore* w ith fad e d e p th .
T h e c o n c l u s i o n was a r r i v e d
>
1
•- .
.
a t.b y a c o n s id e ra tio n of th e p h y sic a l path
len gth
of
the
«
echo
and
•
not * th e 'p h a s e p a t h 'l e n g t h .
It
appears th a t
A
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
the
l a t t e r . '- w o u l d be more a p p r o p r i a t e
is p o in te d
can e x i s t
len g th .
actu al
d ifferen ce
tim e d elay
.
F in ally ,
.
Rummler
[62]
u s e d *a
th ree
*
exam ine
ch an n el,
«
tran sm issio n
B ased on e x p e r i m e n t a l
30 MHz
ap p licatio n ,
( b a s e d on t h e p h a s e
\
and t n e v a l u e c a l c u l a t e d - b a s e d on t n e p h y s i c a l
p atn len g th )
to
an
.
*
model
such
i n W eb ster 143] f a s u b s t a n t i a l
betw een th e
i
path
out
for
a
resu lts
model
su fficien t
for
co n d itio n s.
H ow ever,- t h e
to
the *
represent
^
,
«
$
' r
rep resen tin g
, all-
d e l a y ofc 6 ^ 3 n,s i s
observed/
d e la y model i s
situ a tio n
and
channel
^ •s
in ten d ed
not
sh q u ld
n o t , be
^
*
in terp reted
*
as s u c h ..
D i f f e r e n t m ethods f o r
p ro b a b ility
due
to
*
rep o rted
tech niques
in
[63]
and
estim atin g
assum ed
rad io
r
op erating
at d ifferen t
u su ally
b it
sta tistic s,
t a k e n by d i f f e r e n t
Forexam ple,
depth
and
[65]
th e
calcu lated
in terferen ce
th e
how ever,
«
tim e
pow er.
In
m ost
'
seem s t o be l^hat,
cases,
—
o u t a g e on
due
the
system s
Jakes
d elay
by G a u s s i a n
co n clu sio n
au th o rs
w i t h an e x p o n e n t i a l d i s t r i b u t i o n
w h i l e Rumm ler
th at
r a t e s . . W idely
tr a n s m is s io n c h a n n e l can be r e p la c e d
same
outage
sys-tems e m p lo y in g v a r i o u s m o d u l a t i o n
independent fad e
assum ption
*
*
for
th e o utagep r o b a b i l i t y .
in delays tim e;
th e
d ig ital
m u ltip a th p ro p a g a tio n have a l s o been
approaches are
d istrib u tio n
j
e stim atin g
'•
[63]-[65]
» d ifferen t
d elay
c h a r a c te r is tic s - '.
*
concluded
th at,
for
a
w ith a fix e d
p h y sica l
fix e d
channel
he
fix e d
ray
_
tp*
tn e
N oise
of
tn e p e r tin e n t
-
for
w ideband
w ithout d iv e r s ity ^ p r o te c tio n ,
i
th e
d ig ita l
rad io
e s tim a te d outage
*
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
187
tim e
w ill
^xceed
the • o utage
r*#
eh o rt-h au l
8 .£ .3
o b jectiv es
t r a n s m i s s i o n Over a v e r a g e
th at
terrain .!
a v a i l a b i l i t y o b j e c t i v e s be m et,
c
d ig ital
>
are
r e q u ir e d . to
im pfoye
. ' /
*
5
'
r a d i o . ‘s y s t e m s u n d e r
m u ltip ath ,
perform ance of
*
fading
co n d itio n s.
m o s t co m m o n ly u s e d t e c h n i q u e s
are space d iv e r s ity
tw o
com bining
d iv ersity
p ro te ctio n
is
stro n g est
sig n al a v ailab le
sele cted
and
fed
to
- '
,
betw een
it
the
-m ultipath
fad in g ,
the
•*
ap p licatio n s,
of
is
space
u su ally
em ployed jwhereby
*'
'
fro m more t h a n
one' a n te n n a
J
4
th e
and a d a p t i v e e q u a l i z a t i o n .
To m in im iz e th e e f f e c t s
input
sp ecial
•
tech n iq u es
rad io
fcf t
Space D i v e r s i t y Com bining and A d a p tiv e E q u a l i z a t i o n
In o rd er
The
req u ired
i
receiv er.
However,
’- •
u n d e s ir a b le to sw itch
rn ain a n d t h e d i v e r s i t y
the
is
in d i g i t a l
J,
th e
radio
antennas as
-
the
-
*
s w itc h in g '/p ro c e s s
d isco n tin u ity .
.
sig n als
in-phase
'd o n e a t
w ill
The
in tro d u ce
a ltern a tiv e
m ethod i s
fro m t h e m ain and d i v e r s i t y
com bining
techn ique.
th e IF s t a g e .
^ |ro rs
maximum power* c o m b i n e r
one a n te n n a
com bined
is
sh ifted
(added)
[66].
com biner i s
The p h a s e o f
by a c a l c u l a t e d
w ith the o th e r
'y
by,
using
an
essentietiBLy
’
t h e s i g n a l on
amount b e f o r e
sig n al
power from t h e co m b in er i s m a x im iz e d .
th e-
com bining, i s u s tia lly
Q
a
‘ to*
t o com bine & e
antennas
The
An i n - p h a s e
due
so t h a t
is
o u tp u t
a
maximum
power co m b in er d o e s n o t m in im ize in - b a n d d i s t o r t i o n
>•
th e m ajor Im p airm en t to d i g i t a l r ^ d i o s y s te m s .
w hich i s
'
H owever,
the
it
,
t
i
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Wang
*
C om biner,
[6 6]
-
a
4
t
one
p o i n t e d o u t t h a t by u s in g
a maximum p o w e r
*
sig n al
w i t h a f l ^ t s p e c t r u m c a n com bine -with
«
■
w hich
co n tain s
tra n sm issio n
channel)
am plitude s lo p e .
"equalize
the
• t h e u se o f an
[67].
The
an
in-band
to produce
One
common
slop e
adaptive
am plitude
Anderson
S
,
et
eq u alizer
is
[59],
. meet
[66],
spectrum .
resu lts
[29]
rep o rted
appear
by
B arn ett
toi n d i c a t e
tech n iq u es
re lia b ility
are
adaptive
in co rp o rated , w ill
o b jectiv es
for
tran sm issio n .a p p lic a tio n s.
sh o rt-h au l
,
*
Both t h e
/
' *
.
,
t
th at
-
eq u alizatio n
required
to
to p roduce a
d i g i t a l r a d i o s y s t e m s , w he n i n - p h a s e c o m b i n i n g ' a n d
am p lit^ e
is
from t h e c o m b in e r o u t p u t by
fla t
al.
^the
an i n - b a n d
th erefo re
o f su c h an e q u a l i z e r
E x td h s iv e experim eji/tal
by
a sig n al^ w ith
t
s i g n a l w i t h an e s s e n t i a l l y
[28]“* and
(caused
technique
am plitude
fu n ctio n
n u ll
t
tech n iq u es
.o f
in -p h ase
4'
IF,
.
com bining
.
a nd
‘
adaptive e q u a liz a tio n
are
in co rp o rated
in th e d i g i t a l
radio
»
in sta lle d
across
t h e Bay Of F u n d y .
‘j
8.3
«
Perform ance o f D ig ita l Badio A cross th e Bay o f Fundy
(
^
8 .3 .1
System R e l i a b i l i t y O b j e c t i v e s
.
•
>
In o rd e r- t o com ply w i t h th e r e q u i r e m e n t s o f t h e
th e
allow able
one-way
p r o p a g a tio n im pairm ent)
*
*
N j.ctaux' S o u th
d ig ital
system
u n av ailab ility
allo cated
TCTS,
(due
to
to
the
O tter
Lake ■*
r a d i o h o p is* 1 9 . 5 i p e r y e a r [ 6 8 ] .
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
. ' 189
o
v
fading
»
*
The t o t a l o u ta g e tim e ,m e a s u re d
perio d
on
Day® 241
and
d u rin g
242
in
"the
1981'
severe
is
72*2 s .
The
.
propagation
th erefo re
i n d h c e d o u t a g e on t h e
two w o r s t
fading
days
*
#
e x c e e d e d t h e o u t a g e tim e a llo w an ce» * fo r t h e w hole
year. •
8 .3 .2
*
th e
.
■
E xperim ental R e s u lts
„
*
»•
The r e s u l t s o f t h e d i g i t a l form * o f
contain
*
lo w
speed
*
rad io
(6 c m / h )
te st
is
paper c h a rt records
(b)
P r o t e c t i o n C h a n n e l D i v e r s i t y AGC v o l t a g e ;
(c)
P r o t e c t i o n C h a n n e l C o m b i n e d AGC* v o l t a g e ;
*
‘i
P r o t e c t i o n C h an n e l' Eye v o l t a g e ;
*
B
P r o te c tio n Channel A daptive E q u a liz e r
and,
(f)
The
th at
f
P r o t e c t i o n C h a n n e l M a in AGC v o l t a g e ;
(e)
-in
the fo llp w in g p a ra m e te rs:
’*
(a)
(d)
av ailab le
•
S tress
v o ltag e;
A
M ain C h a n n e l B y e v o l t a g e .
v
*
eye
v o ltag e
i s l a good
in d icatio n
o f - the
P(e)
•
,•
•
L'
p e r f o r m a n c e -of t h e d i g i t a l r a d i o [ 3 5 ] a n d c o n s e q u e n t l y i s
#
used for' in d ic a tin g
dystem p e rfo rm a n c e d e g r a d a t i o n s .
D uring
th’e 8 0 9 - h o u r p e r i o d f r o m 3 1 s t J u l y (Day 21 2 ) t o
^
*
3rd Septem ber
[ D ay 246) i n 1 9 8 1 , d i g . i t a l r a d i o p e r f o r m a n c e
•
•
. *■
*
*
■*
» w as o b s e r v e d t o s h o w d e g r a d a t i o n
i n 97 h o u r s .
The tem p o ral
-\
d istrib u tio n
of
t h e s ? 97 h o u r s i s s h o w n in. F i g . * 6 . 1 .
The
\
. d a t a f r o m the* 97 h o u r s a r e u s e d a s t h e
d ata - base
in
the
*
sta tistic a l
,
an aly sis
the
r e s u l t s o f w hich a r e p r e s e n t e d
<>
V
J
S ection 8 .3 .3 .
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
in
It
on
is
seen in s e c t i o n 8 . 3 . 1
t h a t th e fading c o n d itio n s
Day 242 a r e e x t r e m e l y d e t r i m e n t a l t o t h e d i g i t a l
T h e f a d i n g c h a r a c t e r i s t i c s on
C h a p t e r 6 . ' The
ray . p a th
Day 242
radio.
I
discussed
in
were
param eters
a nd t h e h ^ u r s .when
s e v e r e s y s t e m p e r f o r m a n c e d e g r a d a t i o n was o b s e r v e d
. • ■
'
‘
•\
•
d ig ital
radio
is
also
shown
in
F ig. 6 . 9 .
*
o b s e r v a tio n s p e r t i n e n t to th e d i g i t a l r a d io
*
F irst,
tim e
and
is
the
the d i g i t a l
Several
are notew orthy.
delay
time is
r a d i o i s most s e v e r e l y
above 7 n s .
t h e p e r i o d a \ l l i 3 0 ADT (Day 242)
d elay
tim e
from
8 rve—
tS
degraded
P a r t i c u l a r l y dram atic
when t h e d r o p ,
5 ,ns
resu lts
y
in
in
degradation
and - t h e f d i f f e r e n t i a l
am plitude
system
(d ifferen c e
b e t w e e n -the a m p l i t u d e s o f t h e m a i n - a n d s e c o n d r a y s ) .
From
<■
to
0 6 : 00’^ADT
(Day
a
242$ ,
V .
and
the
resto red
p e r f o r m a n c e on t h e d i g i t a l r a d i o .
I
’
1
S e c o n d , a go o d c o r r e l a t i o n a l s o ' e x f s t s b e t w e e n
02 : 00
the
a high c o r r e l a t i o n e x i s t s
betw een
long
delay
••
*
system
degradation.
As shown i n F i g . 6 . 9 , t h e
perform ance of
when
on
_
>
a g a in from 0 8 :0 0 4 t o
-
-
1 1 : 0 0 ADT, t h e m a in an d s e c o n d r a y s a r e o b s e r v e d t o b e v e r y
close
in
am plitude.
T his
c o r r e l a t i o n i s t o be e x p e c t e d ’
s i n c e two r a y s w i t h a b o u t t h e same a m p l i t u d e w i l l r e s u l t 1' irrdeep
n u lls ^due
to
in terferen ce
betw een
the
rays
as
*
•
*
r’
d i s p l a y e d in F i g . 6 .1 0 .
T h e s e n u l l s , when o c c u r r i n g w i t h i n
the
**
**
bandw idth o f th e d i g i t a l r a d i o , w i l l l e a d to
T *
'
"
*
in-band d i s t o r t i o n a n d - th e r e f o r e o u ta g e s .'
channel
ex cessive
To i l l u s t r a t e
t h e com bined e f f e c t s o f lo n g
S
deep
fades
on
the d i g i t a l ra d io ,
delay-
and
•
th e m easured d e la y
V
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
time
'19
A
‘
a nd t h e c a l c u l a t e d maximum
period
from
09:00
to
rtotch , d e p t h
1 1 : 0 0 ADT
(Day
F .ig . 8 .3 t o g e t h e r w i t h t h e Eye v o l t a g e s
AGO
v o l t a g e on t h e d i g i t a l
rad io .
for
a
242)
a r e shown in
a nd
twcj
the
hour
Combined
T h e maximum n o t c h d e p t h
^
*
o f t h e a m p l i t u d e m r i £ s c a u s e d by t h e tw o s t r o n g e s t r a y s was
*
■
-*'■V.
*
’ estim ated
using
t h e m ain ' a n d
second
ray a m p litu d e s as
m e a s u r e d by t h e p r o p a g a t i o n
experim ent.
To e x p l a i n
and
th e c o r r e l a t i o n betw een a lo n g
d elay
tim e
if
*
*
radio
o u ta g e , a s im p lif ie d approach is u sed .
d ig ital
C o n s i d e r a tw o r a y p a t h s i t u a t i o n vrijth a r e l a t i v e
betw een
in
F ig.
of
the
rays.
The e q u i v a l e n t a m p litu d e t r a n s f e r
J >
f u n c t i o n . o r t;he t r a n s m i s s i o n channe.1. i s o f t h e
form
showri
*
A*
delay
.
3.3.
frequency-
w ith
i
am plitude
the
nu lls
separated
in Eq.
(3 .8 ).
Af = ( 1 / A t ) a s g i v e n
C onsider
*
The
now
a
w ideband
response
is
in
radio
p erio d ic
in
frequeridy
system
by
having
a
‘
,
bandw idth
of
B Hz
a nd
o p e r a t i n g orwone o f
r a d i o c h a n n e l s a s shown i n F i g .
'
V
■
.
*
■
th at
.
two r a y s a r e
•
received,
8 14..
G iven
the p r o b a b ility ,
«
the a llo c a te d
the
condition
P
, t h a t the
,n
radio channel w i l l c o n ta in
•
•*
*
an i n - b a n d n u l l
i s g i v e m by
Pn " f ? = B ' AT
{BtlY
*
,
t
For a fix e d
/
ra d io bandw idth,
,
.
the p r o b a b i l i t y o f
the
radio
»
■
channel
containing
p ro p o rtio n al
an
in-band n u ll
t o t h e d e l a y t'im e.
th erefo re
is
d ire ctly
The p r o b a b i l i t y o f a
,n u ll
*
o ccurring
w ithin
channels
%
the d elay tim e, g iv en
versus
o f b a n d w i d t h 30 MHz and 40 MHz
the
"
co n d itio n
th at
»
•
1
^
. *
„
k
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
two
•
ray
T
■* \
T
x
■« %
i >
■>»
V °
9
•\ * •
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closed
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4-
-
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1
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I----------h s— I----- -+ —
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4—
r
4-
regular c h a n n e l e y e v o lta g e
l---------1—
l .
I
‘ I
JO
10
* K f 4‘ 7 -
m
r
r
i
i
i
r
T
T
i
T
w
r
i
i
r
r
p r o t e c t io n channel e y e voltage.
4---------1-
n o r m a l level
H
1
h
1
h
£
C D
X)
a
-AO
■a
3
Q.
-60
£
<
p rotection c h a n n e l
JL
±
J59
Day 2 4 2
F ig.
8.3
I
i
c o m b in e d AGC
I
»
10
ADT
E f f e c t * 1o f " ‘l o n g r e l a t i v e d e l a y t i ^ n e ’ on. d i g i t a l
(radio p e rfo rm a n c e .
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
i
11
-
ch.1
R a d io c h a n n e l s ^ w i t h
channel b a n d w id th s
of B H z.
Ch.3 c h .4 ch. 5 c h .6
ch.2
c,
i
^ A m p l it u d e r e s p o n s e
A d u e t o t w o r a y s w ith
( r e l a t i v e d e l a y t im e a t
freq u en cy
F ig.
0
8.4
D iagram t o i l l u s t r a t e the, p r o b a b i l i t y t h a t
- a p a r t i c u l a r r a d i o c h a n n e l w i l l c o n t a i n an
i n - b a n d n u l l . , g i v e n t h e c o n d i t i o n t h a t two
ray p ath s a re receiv ed .
.
'' *
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
paths
w ith
relativ e
<■
F ig .
d elay
Ax
is
is
' ’
show n *in
‘
8 .5 .
The
. *
d ig ital
radio
b an d w i d t h * . ®f 40 MHz.
d elay
tim e o f g r e a t e r
used
in
th e
in-band
null
ekpSXiment - h a s
a
From F i g .
8 . 5 , * ii: i s s e e n t h a t f o r a
-«-♦ %
8 ns,
th e
p ro b ab ility
o f #an
than
*
is g re a te r
than
V
32 %.
m
'
The above s im p le a p p r o a c h h a s
im p o rtan t
im p licatio n s
:, ■
c
r e l a t i o n t o fre q u e n c y d i v e r s ity. p r o t e c t i o n ^ s c h e m e s .
It-
in
is
p resep t,
,
se.en t h a t N t o r ’two r a y p a t h s ,
betw een , n u l l s
For
isrrn
p lo tted
the
the
in F i g .
frequency
- sep aratio n
o r t i o n a l .to th e d e l§ y t i m e .
t h e r a n g e d£ d e l a y
experim ents,
the
tim es observed
in
the
p ro p ag atio n
nulL s e p a r a t i o n v e r s u s 1 th e d e la y tim e i s -
8 .6 .
For d e la y
n u ll-i-p e p a r a t ion
'is
tim e s * o f ‘g r e a t e r
I#Ss
than
than 8 n s,
1 2 0 MHz.
F o r 40 MHz
i
bandw idth c h a n n e ls ,
" m o re
than
th en ,
one o u t o f
U nless th e
an i n - b a n d
th ree
-n u ll
w ill
occur
c h a n n e l s a s shown i n F i g .
frequency of the d i v e r s i t y p r o te c tio n
on
8 .7 .
channel
is
p ro p etly
sele cted
• (so
th at
n u lls
do
not*
Occur
*1
s i m u l t a n e o u s l y ^>n t h e r e g u l a r and t h e p r o t e c t i o n c h a n n e l s ) ,
no
im provem ent
w ij .1
be O f f e r e d
*
,A g o o d e x a m p l e
by
•
p ro te c tio n
radio
channel.
experim ent.
The
m ain
is
sw itching to
*
*.
found
and
test
*
121.5
d elay
are
MHz.
*■
in th e d i g i t a l
p ro te c tio n channel
'
freq u en cies
the
9
*
in th e O tte r.L a k e . - N ic ta u x S outh d i g i t a l r a d io
■.
7.78611
and
As a r e s u l t ,
tim e
of
*
7 . 8 6 7 5 9 - GHz
a
if
s i t u a t i o n w ith
a two
g reater"
path
separatio n
than
( 1 / 1 2 1 . 5 x l 0 6 ) ■ 8 . 2 3 - ns o c c u r s w ith' s u f f i c i e n t
'
of
a
ap pro xim ately
fade
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
depth
/ '
/ r
5; V ;
J ft
i
195
I
B = 4 0 MHz
0»
'c
c
o
JC
(
0.4
3 0 MHz
O 0
o .2
0.2
>s
** o
?.O ‘.£
jC
O
+;
& *
0
0
10
5
Ret. d e l a y o f se co n d ' ray
(ns)
B . . . b a n d w id t h of r a d io c h a n n e f
4.
Fig. ,8.5
15
.
,
-»
Probability of in-band nulls versus
relative- delay of- second ray.
6Q0
t
5 £ 200
S'*
Oi ■*-*
Re,I.’ d e l a y o f s e c o n d ray
Fig.
8C6
, >■
(ns)
N ull s e p a r a tio n v e rsu s r e l a t i v e
d e l a y o f s e c o n d r ^ y ,.
,
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
'
,
ch.1
ch. 4
c h .2
ch. 5
ch.6
-r a d io *
c h a n n e ls
*•
freq u en cy
* A'f l e s s
F i g . ^ 8 .7
t h a n 120 MHz for
aT
la r g e r t h a n - 8 . 3 ns
O c c u r r e i ^ ^ o f i n - b a n d n u l l s on a d j a c e n t
r a d i o c h l R i e l s . w i t h b a n d w i d t h s o f 40 MHz,
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
4
to
cause
lik ely
E xcessive
on t h e main c h a n n e l ,
t o be o c c u r r i n g on t h e p r o t e c t i o n
sw itch
to
the
. The s i t u a t i o n
used
BER
p ro te ctio n
i s „ w o r s t when
c h a n n e l and t h u s a
channel w i l l n o t be s u c c e s s f u l.
(lxN )
in which one p r o t e c t i o n
N regular
t h e same i s
p ro te ctio n
channel
is used
schemes
are
for p ro te c tin g
T h e a b o v e two p a t h c o n d i t i o n t h e n w i l l
/
in a s i t u a t i o n in w hich s e v e r a l c h a n n e l s w i l l s u f f e r
resu lt
channels.
sim ultaneous
outages
and
therefore
com pete
for
the
p r o te c tio n channel.
S ta ris t ical
8 .3 .3
R esults
%
of
U s i n g a s d a t a b a s e t h e 97 h o u r s when
the
perform ance
*
,
"
'
t h e d i g i t a l r a d i o was d e g r a d e d , t h e d i s t r i b u t i o n s o f t h e
*
'
/
d e l a / 1 tim e,"
the
" m a in
and
%*
second
•
am plitudes,
and
the
*
estim ated
rays),
maximum
*fhde
depth
were c o m p u ted .
The d e la y
tim e~"distr i b u t i o n . is
m edian d e la y tim e i s 6 .8 n s ,
and 5 . 8 n s f o r
same
( c a u s e , by t h e t w o s t r o n g e s t
ex ceeded 8.25 ns f o r
illu stratin g
compared w ith v a l u e s o f 4 .7
th e non-fading
experim ent.
M ore
shown *in F i g , ^ 8 . . . T h e
a nd f a d i n g
im portant
20 % o f t h e
d ata bases for
i& t h a t
the
th e d elay tim e
t i m e f or. t h i s
t h e ' c o r r e l a t i o n J ib e t w e e n l o n g
ns
data
base,
d e la y tim e
and
♦
d i g i t a l ra d io perform ance d e g ra d a tio n .
The' r a y p a t h a m p l i t u d e d i s t r i b u t i o n s ,
d istrib u tio n
in F ig .
rays
8 .9 .
for
a s w ell
d f t h e e s t i m a t e d maximum f a d e d e p t h ,
The m edian a m p litu d e s o f
th is
d ata
base
are
as
a r e shown
th e m ain.an d
-7 .5
dB
the
and.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
second
- 1 7 . 0 dB
15-
K.
t>•
10-
O
4*
■o
>
O
'Z
CC
0OX)1 0.1
5
10
96
50
P e r c e n t a g e of t i m e
aT
,99
99.9 -99.99
exceeded
(
Fig. 8.8
10
Delay time distribution during periods
when the digital radio suffered
impairments.
-
CD
■o
M oin ray"'
*
-
10-
Q.
-
20-
Second
ray
E
<
-3 0 -
C o lc u la te d r e s u l t a n t
minimum a m p litude
-5 0
0.01
Fig. 8.9
0.1
90
,
50
5 10
1
Percentage of tim e am plitude „exceeded
99
9 9 .9 99.99
Amplitude distribution during periods when
the digital radio suffered impairments.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
respect^fch.y
r l 8 . 5 dB
(compared w i t h median v a l u e s
for
the
fading
These r e s u l t s appear
d ig ital
radio
in
in d icate
am plitude,
modest i n c r e a s e in th e
The d i s t r i b u t i o n
caused
- 4 . 0 d B . and
t h e same e x p e r i m e n t ) .
th a t the
outages
the
_ ' ***
shown i n F i g . -ff.9 and i t
in d icate th a t
accom panied
by
a
on
the
rela tiv e ly
second ra y a m p l i t u d e .
*»»
o f t h e maximum f a d e
depth
by
<
.
resu lts
data
of
a r e c a u s e d m a i n l y by a s u b s t a n t i a l d e c r e a s e
i n t h e mai n r a y
am plitude)
199
*
%
m ain
(minimum *
and seco n d ra y s a r e a l s o
•*
■
h a s a m e d i a n v a l u e o f - 1 3 dB.
The,
t h e two r a y s a l o n e c a n c a u s e f a d e s o f
more t h a n 40 dB f o r more
than
ap proxim ately
(t %
of
the
tim e.
F inally,
are
i s i n t e r e s t i n g t o ncrte t h a t ^ . t h o u g h t h e r e
I
*
97 h o u r s * (12* % o f
the
to tal
ddta base of
. only
777 h o u r s )
d ig ital
of a l l
1981
it
d u r i n g which' e y e c l o s u r e s w e r e o b s e r v e d
rad io ,
on
the
t h e same 97 h o u r s c o n t a i n a p p r o x i m ^ t j f e y v ^ l %
th e long d e la y
time v a l u e s
( >9 ns)
recorded
in
the
experim ent.
T h e s e h o u r s a l s o c o n t a i n 70 % o f a l l t h e
<>
r e c o r d e d f a d e s t h a t are in e x c e s s
of
20 dB i n
the
1981
1
experim ent.
.
8.4
.
Summary
, The main i m p a i r m e n t t o t e r r e s t r i a l
m icrow ave
d ig ital
*
radio
system s
is
in-band d i s t o r t i o n .
T his in c lu d e s bpth
/
•
,
'/
in -b a n d am plitude d i s t o r t i o n
a nd d e l a y
d isto rtio n .
The
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
degradation
due t o
th a t o f delay
in co rp o rate
*
eq u alizatio n
am plitude d i s t o r t i o n
d isto rtio n .
in-phase
D ig ital
.d iv e rsity
techniques
are
is
m ore s e v e r e
rad io
system s
com bining
rep o rted
to
than
w hich
and
ad aptive
provi.de
adequate
p e r f o r m a n c e on t y p i c a l o v e r - l a n d LOS p a t h s .
k
The p e r f o r m a n c e o f a d i g i t a l
radio
in stalled
across
*
Bay
of
Fundy m i s s e d t h e r e l i a b i l i t y o b j e c t i v e s by a
/
th e
w ide m a rg in .
by
T h e p o o r p e r f o r m a n c e . , was f o u n d t o
'u n u su ally ,
severe
large
fad in g .
d elay
Thq,
tim e
d ig ital
valu es
v u ln erab le,
radio
is
ray
p artic u la rly
»
in th e ca se o f
second
caused
and s i m u l t a n e o u s
*
the
be
o
larg er
two r a y p a t h s ? ,
tHten
to
d elay tim es of
appro x im ately
8 ns.
When
*
ad d itio n al
rays
are
t h e m ain r a y a m p l i t u d e
lay ers)
* is
p resen t,
th e s i g n i f i c a n t d ecrease, in
S' J
(due to d e fo c u s s in g
by a t m o s p h e r i c
se e n to b e an i m p o r t a n t c a u s e o f d i g i t a l
fa ilu re s.
-
’
When a t
'
least
rad io
'
two r a y p a t h s
: %
e x is t w ith
/!/ :f
a d elay
tim e o f
i
m ore’
*
1
^
than
app ro x im ately '
8 ns,
frequency d i v e r s i t y p r o te c tio n
i
System s
is
- sig n ifican tly
^ circu m stan ces,
th e
be
carefu lly
for
th e rad io p ath s
delay
tim e
bandw idths
e f f ebtdfyeness
of
I
f o r w ideband
d ig ital
radio
/.
;
reduced.
Under
such
frequency of
sele cted .
v a l u e # "’ a r e
( e . g . • 40 MHz)
\
th e 'p r o te c tio n
F in ally ,
across
th e
it
r
is, no ted
c h a n n e l inust
*
4 * 1
t h a t a t l^tast
t h e Bay o f ’ F u n d y o n
w hich
long
f r e q u e n t l y o b s e r v e d , w ide c h a n n e l
•
appear
4
t o be -eF^father
in ad eq u ate
r
choice.
S ig n ifican t
use o f d i g i t a l
♦
i
H
im provem ents
shoul/3 r e s u l t fro m t h e
*
•
l a d i o system s occupying n a rro w e r b a n d w id th s.
t
*
.
,4
*
4 ■*
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
;
C hapter 9
SUMMARY AND CONCLUSIONS
r-
The p r o p a g a t i o n o f m ic ro w a v e s i g n a l s
Fundy
has
been
exam ined in t h i s
e x p e r i m e n t s were p e r f o r m e d a t
sep arate
resu lts
the
heavy
across
of the experim ents p ro v id e
propagation
fading
m echanism s
th esis.
X-band
lin e ^ o f - s ig h t p aths
Two p r o p a g a t i o n
^frequencies
on
two
t h e B ay o f F u r id y .
The
im portant
which a r e
activ ities
a c r o s s t h e Bay o f
u su ally
in sig h t
resp o n sib le
observed
in to
for
in
the
th is
geographical area.
a*
The m ajor cau se o f m icrow ave s i g n a l f a d in g a c r o s s
bay
is
th e sea r e f l e c t i o n . .
ray
is g en erally
over-w ater
c h aracteristics
are
not
u su ally
10 GHz,
reflected
lo ss
*
rela tiv e
'
the
to
in d icate
ray
g rad ien t,
ex ist
»
and
on
such
ray
path
understood.
The
n atu re
*
w ell
th at,
is
at
stab le
a
frequency of
a nd
suffers
a
e x c e p t under v ery
.
Under norm al c o n d i t i o n s o f a un ifo rm
th e d e la y tim e o f
th e d i r e c t ray
A ylesford
to
o f o n l y a few d e c i b e l s ,
rough sea c o n d itio n s .
refractiv ity
known
exact
resu lt^
reflectio n
a nd
the
experim ental
the
A lthough a s p e c u l a r l y r e f l e c t e d '
expected
p ath s,
the
-
is
the r e f l e c t e d
of the o rd er
O t t e r L^ke p a t h
of
2.5 ns
and 4 . 5 n s f o r
ray
for
the O tte r
i'
Lake - N ic ta u x South p a t h .
to
the h ig h e r
The l a r g e r d e l a y v a l u e
antenna h e ig h ts
in th e
second e x p e r im e n t.'
•
*
*
v
^
*
'
201
is
«
*0
.
‘
R e p r o d u c e d with p e r m i s s io n of t h e co p y rig h t o w n e r. F u r th e r r e p r o d u c tio n prohibited w ith o u t p e r m is s io n .
due
The m o st s e v e re
caused
ex ist
by
the
extrem e
m ajor
fading o bserved
across
the
bay
p re s e n c e o f atm osphere l a y e r s w ith in
neg ativ e
in flu en ce
of
g rad ien ts
in
atm ospheric
refractiv ity .
lay ers,
was
which
The
when t h e y o c c u r
below th e a n t e n n a s , a r e :
,
(1)
to cause d efo cu ssin g of
su b stan tially
reduce
the d i r e c t
its
ray
am plitude
and
th erefo re
{ a t t i m e s b y m o re
. t h a n 10 d B ) ;
(2)
to
im prove t h e c l e a r a n c e o f t h e
u n d erly in g
terrain
and
reflected
th erefo re
ray above th e
increase
its
am plitude;
(3)
*
to in c re a s e
ray;
(4)
to
raise
d elay
tim e
of
th e
th e a n g l e s - o f - a r r i v a l o f both th e
reflected
‘
re la tiv e
reflected
and,
the
€T
th e
d ire ct
and
ray s.'
.
When t h e l a y e r o c c u r s
antennas . a re
w ith in
at
a
h eig h t
the l a y e r ,
such
atm ospheric
th at
both
ray p a th s are
*
in tro d u ce d .^
The
d elay
atm ospheric
p aths
are
LOS
p aths
a nd
tim es
u su ally
therefore
are
asso ciated
w ith
less
than 6 ns fo r
less
d etrim en tal
such
ty p ical
to
the
c.
o p e r a t i o n o f w ideband com m unication s y s te m s .
In th e p resen ce of atm ospheric
of
the
reflected
• 6 ns f o r
ray
is. f r e q u e n t l y
lay ers,
in creased
th e A y le s fo rd - O t t e r L^ke p a th
th e .d e la y
to longer
and 8 n s
for
tim e
than
the
9
O tter
Lake
-
N ictau ^T ^o u th p ath .
•
D elay tim es o f h ig h e r
*
t h a n 14 n s w e r e o b s e r v e d d u r i n g o n e
-
fading
peis^od^
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Lon g
203
* 4 e l ay
tim es
t
of
t h i s m a g n i t u d e a r e ‘f o u n d t o b e e x t r e m e l y
*
d etrim en tal
*
*
to
the p ro p e r
operatio n
of
w ideband
d ig ital
•
radio
system s.
In p a r t ic u la r s
frequency d iv e r s it y p r o te c tio n
sev erely
effectiv en ess
of
unde(£ t h e s e c i r c u m s t a n c e s
is
reduced.
A square
was
the
«
law r e l a t i o n s h i p
obtained
resu lts.
for
deep f a d e s ,
P ( V s L ) 11 L 2 ,
f o r ^ th e fad e depth d i s t r i b u t i o n
T h e more s e v e r e
fading
in 1981 i s
of. the
reflected
1980
in
a
P(V < L ) ccL1 * 6 r e l a t i o n s h i p .
These th e n ,
i
’
*
fromt h e
for
are
some o f
p ro p ag atio n experim ents,
as u b j e c t m a t t e r o f
and
co n clu sio n s
therefore
are
th is
-are
noted
for
A lth o u g h most o f
m ain
co n clu sio n s
ft
recognized
scppe-and
not
is
natu re,
e x h au stiv e .
th e
drawn
th at,
resu lts
S everal-
p o in ts
f u t u r e w ork.
the u s a b le
data
o b tained
•“v
the
from
p ro p ag atio n
e x p e r i m e n t s h a v e b e e n p r o c e s s e d , mucl), v a i l u a b l e
in form ation
is
still
F u rth er - a n a ly sis
*
k
th e
t
p attern
*
of
process
in d iv id u al
m icrow ave
is a ra th e r
the
o rig in a l
sweep f r e q u e n c y
in sig h t
d ata.
r e c o r d s by
in to v arious other
•
U n fo rtu n ately ,
the
tim e consum ing t a s k .
d iag n o stic
system
axe n o t r e s o l v e d .
p aths c o u ld le a d
in
pro p ag atio n .
The e x p e rim e n ta l r e s u l t s
m icrow ave
. paths
of
s y n th e s is sh ould p ro v id e
aspects
,
*
co n tain ed
revealed
a
weakness
in
the
in th a t very s h o rt delay ray
F u rth e rm o re ',
these
to s p u rio u s v a r i a t i o n s
in
s h o r t d elay
ray
the slo p e p f
the
*
sweep f r e q u e n c y p h a s e
accurate
■
and
r e c o r d s w hich o t h e r w i s e
v aluable
inform ation
s
on t h e
would
yield
in d iv id u al
i
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
ray
path
an g le-o f-arriv al.
A
.
scheme
d ifferen t
■
fo r m easuring t h i s l a t t e r
co n d itio n s
m ore
re lia b le
*
param eter under m u ltip a th
should be d e v e lo p e d .
F in ally t
lo catio n
and
it
\
n o t e d t h a t t h e Bay o f Fundy i s an i d e a l
*
i
in v estig atin g
various
propagation
effects
for
is
w hich a r e a s s o c i a t e d w ith a t m o s p h e r i c
rela tiv e ly
frequent
occurrence
of riy e rs
One i m p o r t a n t a s p e c t t o b e s t u d i e d ,
d ep o larizatio n
re c o m m e n d e d
effects
th at
by
for
due
in t h i s
exam ple,
a ny
such
fu tu re
stu d y
hum idity,
in
%
*
\
'?V■
\
\
'
the
It
a nd r e f r a c t i v i t y
%
■
is
should
t
.
reg io n ..
is
be
m easurem ents of th e v e r t i c a l
atm osphere.
■
the
c
sim ultaneous
p r o f i l e s of Jtem perature,
:
to
o f such a tm o s p h e r ic l a y e r s .
,
accom panied
lay ers
■
R e p r o d u c e d with p e r m i s s io n of t h e co p y rig h t o w n e r. F u r th e r r e p r o d u c tio n prohibited w ith o u t p e r m is s io n .
/
the
APPENDIX 1
»
.
*
Dimensions, of the f i r s t Fresnel Ellipse on the Ground
for Specular Reflection on LOS Microwave Links
<
*
C onsider
s how n i n - P i g .
first
#tre
f
t'o t h e p a t h ,
lin e-o f-sig h t
g i v e n by E q.
i
•»
The l e n g t h s
E llip se
of
and
the
g.
earth
surface
sem i-axes
- For
th e
of
d ire c tio n
propagation
from
A'
to
th e p ath,
th e
Th e
w avelength.
In
+ r 2)
(Rj
th e
d ire c tio n
p arallel
to
such t h a t
+ R2 ) =- \
.
(A 1.2) ’
c o s i n e - r u l e a p p l i e d t ^ t r i a n g l e AOP g i v e s
r j 2 = Rj-2 + f 2 _ 2Rj f . c o s
* '
-
f.c o s y ) 2 + . ( f .s in y ) 2
m o s t LOS m i c r o w a v e
f << R2; u s u a l l y
y
'1
= (Rj
For
as
(Al.l)
the p o in t P i s 'l o c a t e d
(r,
B
h
g = I r7 + r 7
X is
the
thus
AR1R 2
w here
as
th e sem i-ax is g i s e q u iv a le n t to
case *fo r
(2 .1 9 ),
K
'i
■
from a p la n e
'
A l.l.
Fresnel
perpendicular
th e
•
th e-reflectio n
«
.
•
are
lin k s,
th e
satisfie d .
co n d itio n s
(A 1.3)
f
<< R j
and
A pplying th e b in o m ia l
*
app ro x im atio n
«
k
-
.
«
(a + h f 2 * a 3 ' + i
»
a ^ .b
f o r a << b
>
205
/
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
*
'
(A 1.4)
206
-«
A , B . . . a n t e n n a s a t th e link t e r m in a ls '
A*............. t h e i m a g e o f A
0‘
. r e f l e c t i o n point
Y .............a n g l e of r e f l e c t i o n
a
, . F ig.
A l.l
'
\
•
'
A
The F r e s n e l E l l i p s e i n t h e c a s e o f
s p e c u l a r r e f l e c t i o n o n LOS p a t h s .
■\
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
*
t o Eq;
(A 1.3)
g iv es
r i
•
For f
,
. ( R i ..
...
~ V
- r i
*
..
, f 2 .s i n 2y ,
-t 2 ( r i . f . c o s y )
f - c o s y)
*
#
becomes
R2 +
Eqs.
(A1.5)
(
f 2 . s i n 2Y
■ ' -
t r i a n g l e BOP g i v e s ,
r 2 -
Com bining
, l
•
, Eq,. ( A l . 5 )
<< R j
S im ilarly /
f
for f
. (A 1.6)
<< R ,
f 2 .sin2Y
.2R 2
( A 1 . 3 ) r,
(A1.7)
(A1.6) ,
and
(A1.7)
one
ob tain s
■
* «
le n g th of th e F re sn e l E llip s e
th e
*
.
XRiR2 1
f *
for
s m
an aly tically .
accounted
th e
a curved e a rth
However,
for
by. t h e
d ire c tio n
sem i-axis
is
( A 1 .8 )
Rj +R2
r e f l e c t i o n from a p l a n e s u r f a c e .
The c a s e f o r
In
y
of
th e
given by
use
p arallel
first
[2 4J
F
the
of
i s n o t a s s t r a i g h t forw ard
earth "
a
to
c u r v a t u r e , ' ^m'ay
d ivergence
th e
F resnel
p ath ,
E llip se
co effici-en t,
th e
for
len g th
of
be
P.
the
a curved e a r th
* <*
AR i R2
= Df = - r - 9 ---IX
sin y „Ri+R2
The d i v e r g e n c e c o e f f i c i e n t ,
D,
(A l.'9 )
i s g i v e n by
. -2 RiR2
1 +
where a e i s
d ire c tio n
th e
a ( . CRi+R2 ).”. s i n
effectiv e
perpendicular
to
cu rv atu re
th e
(A 1.10)
y.
p ath ,
of
th e
the
earth /
effect
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
In
th e
o f ^earth.
cu rv atu re
d im ension.
does
not
ap p reciab ly
The l e n g t h
p erp en d icu lar
of
d ire c tio n
th e
to
affect
first
th e
path
th e
Fresnel
for
Fresnel
E llip se
a curved
Zone
in
earth
th e
is
thus
7
AR i R2
h
R1+R2
1Y
v
y
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
(A l.ll)
*
r
* •
‘
APPENDIX 2
Soaaary of Diagnostic Systea Parameters
4
k
*
1
•
%
T r a n s m itte d power:
30 dBm
T r a n s m it antenna-:
4 ft
8 ft
R eceive a n te n n a s :
2 f t diam eter p a ra b o lo id s
v e r t i c a l l y s p a c e d 3” m
F requency sweep:
9 . 5 0 0 - 1 0 . 5 0 8 GHz, 19 80
9 . 5 0 5 - - * 1 0 . 5 1 3 GHz, 19 81
64 s t e p s , . 16 MHz
per ste p
S w ee p t i•m e :
1.28 sec
R e p e titio n perio d :
. * .
‘
R ecording:
.
diam eter
diam eter
p a r a b o l o i d , 19 80
p a r a b o l o i d , 19 81
10 s e c ,
'
am p litu d e and phase
d i g i t a l , 8 b i t s each
A
%
I
t
/ ‘
*
*
*
209
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Appendix 3
D e t a i l s o f t h e D ata A c q u i s i t i o n System
A3.1
S y s t e m Memory Map
Memory
A ddress
\
FFFF
D escription
8K RAM
EOOO
IK EPROM - s y s t e m t e s t r o u t i n e s
B400
IK EPROM - d a t a a c q u i s i t i o n p r o g r a m
BOOO
3K EPROM - s y s t e m m o n i t o r p r o g r a m
AOOO
8K RAM
.,0000
2 10
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
r
*
2 11
A3.2
System I n p u t / O u t p u t
(I/O )
P ort A llo catio n s
Port
A d d r e s s _______________________D e s c r i p t i o n _______
00
01
02
03
10
11
12
13
14
15
16
17
FC
FD
FF
C assette In te rfa c e P ort
*
IMSAI
P a r a l l e l I / O P o r t (2 x 8 - b i t )
8080
S e r i a l I/O P o r t
MIO
C o n t r o l a n d S t a t u s o f MIO b o a r d J
8 x 8 -b it p a r a lle l in p u t p o rts for
i n t e r f a c i n g to d i a g n o s t i c system
L
C o n tro l and S t a t u s
P a r a l l e l I / O (1 x 8 - b i t )
] MITS 8 8 - P I O
F ro n t Panel sense sw itch es
1 x 8 -b it p a r a lle l in p u t p o rt
\
>
' V
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
A 3 .3
System C o n f i g u r a t i o n .
(1)
C hassis,
F ront P anel,
- ALTAIR 88 00
(2)
!
and D is p la y :
..
C e n tra l P ro cessin g U nit:
- MITS 8800
* (3)
Memory:
r
( a) RAM —
*
I n d u s t r i a l M icro S y stem s
I S - C 0 0 2 3 1 8K memory b o a r d ,
(b)
EPROM — E c o n o ro m 2 7 0 8
Godbout E l e c t r o n i c s ,
(4)
2 u n its
Ca .
In te rfa c e boards:
*
(a)
2 p arallel
(b)
I/O + 1 s e r i a l
I/O p o r ts
PIO — MITS 8 8 - P I O b o a r d
1 p arallel
(c)
/
MIO — IMSAI 8 0 8 0 >MI0 b o a r d
I/O p o r t
8 x 8,. b i t p a r a l l e l
in p u t board
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
i
APPSHDIX 4
Parameters of.the Propagation Paths
Year
19,80
P a th Length
80.025
MB S i t e
iTocation
L atitu d e e
L ongitude
Ground E l e v a t i o n
A ntenna H e ig h t
(above ground)
D i a g n o s t i c System
D i g i t a l R adio
198 1
km
O t t e r Lake
45® 22 *10" N
6 5 > * 6 '2 3 " W
279 m
6 m
1 -1 5 0 .5
213
O t t e r Lake
45*22*10* N
6 5 * 4 6 '2 3 " W
279 m
69 m
’ 79 m
L o catio n
A ylesford
L a titu d e
45*04*26" N
Longitude
6 4 * 5 0 '3 0 " W
Ground E l e v a t i o n
239 m
Antenna H e ig h t
(above ground)
D i a g n o s t i c System
14 m
D i g i t a l R a d ip , main
D i g i t a l R adio, d i v e r s i t y F r e e S p a c e L o s s @ 10 GHz
; 8 0 . 3 7 5 km
dB
*
N ic ta u x South
44*52*00" N
65*02*10" W
216 m
81 m
79 m
55 m
m
- 1 5 0 . 5 dB
-
*
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
APPENDIX
Analysis of Sweep Frequency Amplitude Records
C onsider
*
\:
*
and
th e
i,
rays.
The
v ecto r
ad d itio n
vjhere
0 =
a
resu ltan t
of
w .A t
the
is
v aries
A5. 2 .
a F o u rier
of
two
re la tiv e
A is
sig n als
phase
as
w
is
»
of
A w ith
'
betw een
in
F ig.
betw een
sw ept
th e
manner
e
am p litu d es
At
shown
q u asi-sin u so id al
The v a r i a t i o n
of
g e n e r a t e d by
d ifferen ce
*
frequency
in ^a
receiv ed rays
^
r
delay-^tirne of
am p litu d e
two
th e
As ‘ t h e
#
am plitude
F ig.
case
, .w ith
sig n als.
*
th e
may b e
serjes
A 5.1,
t h e *two
J
resu ltan t
as
shown
in
expressed
as
^
A = A.q + A'..COS 0 +-...-+ A i .cOS iQ + ...
f
w here
A
average-
(A$.l)
•
and
o
th e
(dc
A,
a re ,th e
com ponent)
and
F o u rier
th e
c o e f fic ie n ts of
fundam ental
th e
com ponents
resp ectiv ely *
From F i g .
A =
A 5.1,
(r x
2
th e am p litu d e A i s
+ r
w hicli c a n be w r i t t e n
2 2
g i v e n by
- 2 r xr 2 . c o s '0)^
A
(A5.2)
as
. f
A = i r x 2 + r 2 2)H
Tf k2 .
lr 2
-.Cos
r j 2+ r 2 2
(A5.3)
0
Eq*
( A 5 . 3 ) may b e e x p r e s s e d i n t h e f o r m o f E q . ( A 5 . 1 ) b y
■
•' " •
-"-J
' ' - 1 •
^—e x p a n d i n g - t h e s e c o n d t e r m o f E q . ( A 5 . 3 ) b y t h e h i n o m i a l
series
v
and
th e
r e s u l t w ith
Eq;
co sin e
CA5.1)
ex p an sio n
'
g iv es
th e
fo rm u la.
\ E q u atin g
^
i
'
co efficien t^ A ian d
2 14
*
'
,
*
,
* ‘
. **
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
th e
A x as
2 1 5.
F ig.
A 5.1
The v e c t o r a d d i t i o n o f t w o . s i g n a l s w i t h
° a r e l a t i v e t i m e d e l a y o f Ax.
)
Frequency
F i g . A5.2
A m p litu d e 'c h a r a c te r is tic s o f th e
r e s u l t a n t o f two s i g n a l s w i t h r e l a t i v e
t i m e d e l a y o f Ax.
v
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
(first
fiv e
term s in each
series
in clu d ed )
*
A o * ro (1 +
" 0.0625 k 2 - 0.0146 k 1*
-0.00641 k 6 - 0.-00358 k 8 ]
♦
(A5.4)
%
and
1- V
1
= tj(l + — )^ [0.5 k + 0.0469 k 3 + 0.01709 k 5
A
R2
‘
.
+ 0.00881 k 7 +,0.00537 k 9J
w here
Eqs.
Y*
2R
k = -------1+ R 2
(A5.4)- a n d
and
(A 5.5)
(A5.5)
*
1
R = —
ro *
are
i n t h e form
Ao “ r 6 * A t o
(A5.6)
and .
*
Ai
-
•
r j . Ar j
(A5.7)
f
. *
w h ere Ar^
w hich
and
depend
A rr are
on
th e
re a rra n g in g Eqs.
th e
scalin g
r a t i o R.
(A 5.6)
facto rs
Expressedin
an d (A 5.7)
^r o ^ d B =
^Ao ^ d B ”
^Aro^ dB
^r ^ d B =
^A l ^-dB ”
^Ar 1 ^dB
th e
v alu es
d ecib els
of
and
g iv es
'
(A 5.8)
and
The
actu al
ray
o btained
from
valu e
th e
th e
of
of
“
a m p litu d e s r Q and
th e . valu es
sweep
A
and
o
frequency
A,
1
th e
sweep r e c o r d .
The
r x *t h e r e f •o r e
.
A
am plitude
fu n d a m e n ta lcom ponent, o b t a i n e d
(A5 . 9)
by.
o
th e average
.
records
and
a«sp ectral
l a t t e r procedure
. r e l a t i v e d e l a y time* b e t w e e n t h e
is
Xh e
may
an aly sis
also y ie ld s
th e
two s i g n a l s .
*
The
P ig.
A5.3
co rrectio n
-
facto rs
as fu n c tio n s of
(A
is.
h t
ai'q
o.
-
and
h i).
Arj
are
These a r e
shown
in
ap p lied
to
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
(8P)
JOjodj u o ipeajoo
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
-cr
218
th e
to
e s t i m a t e d v a l u e s >of ’A^ a n d A x by
give
estim ates
am plitudes.
above
of
r
Computer
approach
and
and
w hich
sim u latio n s
some
of
th e
a calib ratio n
are
and
resu lts
th e
m ethod
d esired
ray
tests
v erified
th e
are
sum m arized
F ig ., 4 .1 0 in C hapter 4.
f' .
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
in
APPENDIX 6
~ ^Sum ary of R e s u lt# o f th e 1980 Experim ent •
♦
The r a y p a t h , c h a r a c t e r i s t i c s o f t h e two s t r o n g e s t r a y s
d u rin g
th e
ten
sum m arized
in
th e
days
fo llo w in g
/
in clu d e:
(a)
sele cted
in
o
9
th e
pages.
1980
experim ent
These
are
c h a ra c te ristic s
*
R e la tiv e d elay tim e
j
(ab so lu te v a lu e ) ,
*
Ax , b e t w e e n t h e
to
ray s given in nanoseconds.
(b)
(c)
M ain
ray
(stro n g est
re la tiv e
to
p erio d s.
|
Second
ray
th e
(weaker
ray)
am plitude,
m edian
value
d u rin g
A
am plitude,
A2,
ray)
A l, 'g iv e n
in
dB
non-fading
given
in
dB
X
re la tiv e
( d)
M a in
t o t h e same r e f e r e n c e l e v e l
ray
an g le-o f-arriv al.
Two
as in
(b).
estim ates
of
th is
j
\ __ ^
p aram eter
records,
(i)
are
o btained
from
th e
relativ e
phase
^hese a re :
AOAS -
e s t i m a t e d from t h e s lo p e o f t h e p h ase
record.
(ii)
AOAI -
e s t i m a t e d from t h e i n t e r c e p t of t h e
phase re c o rd .
In
AOAI
most
rath er
AOAS i s
cases,
than
o ften
by
th e
I
correct
AOAS.
contam inated
T his
by
is
th e
r a y s a n d was i n c l u d e d m a i n l y f o r
of such s h o rt delay
m ain
ray
AOA i s
because
presence
id en tify in g
th e
of
by
v alue
of
short
delay
th e occurrence
rays.
*
given
»
2' 1 9
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1
8
m
■o
0 ;
T— h----- i— i— —i------i----r y 1
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00
APPENDIX 7
Summary of R esu lts of th e 1981 Experiment
The r a y p a t h c h a r a c t e r i s t i c s
during
the
th irty -fiv e
summ arized
in^ th e
days
in
follow ing
o f t h e two s t r o n g e s t r a y s
the
pages.
1$81
experim ent
These
are
c h a racteristics
include:
(a)
R e l a t i v e d e la y tim e
At ,
(absolute v a lu e ),
betw een th e
ray s given in nanoseconds.
(b)
Main
ray
(stro n g est
relativ e
to
the
ray)
am plitude,
A l,
m edian
value
d u rin g
am plitude,
A2,
given
in
dB
non-fading
periods.
(c)
Second
ray
relativ e
( d)
M ain
(weaker
ray)
given
t o t h e s^me r e f e r e ' n c e l e v e l a s i n
ray
param eter
an g le-o f-arriv al.
are
o b tained
Two
from
dB
(b) .
estim ates
the
in
of
re la tiv e
th is
phase
9
recards.
ft
, (i)
T heie a r e :
AOAS - e s t i m a t e d f r o m t h e s l o p e o f t h e p h a s e
record.
(ii)
AOAI - e s t i m a t e d f r o m t h e i n t e r c e p t o f t h e
phase re c o rd .
In most
AOAI
rather
AOAS i s
cases,
than
o ften
by
the
c o r r e c t . m a in
AOAS.
contam inated
T his
ray
AOA i s
is, because
by t h e . p r e s e n c e
the
of
given
by
value
of
s h o r t delay
r a y s a n d was i n c l u d e d * m a i n l y f o r i d e n t i f y i n g t h e o c c u r r e n c e
of such s h o r t d e la y r a y s .
225
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V
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Wang-Leling I g n a t i u s Lam
NAME:
PLACE OF BIRTH:
YEAR OF BIRTH:
POST-SECONDARY
EDUCATION AND
DECREES:
Hong Kong?
„■ »•
:
.1 9 5 5
U n i v e r s i t y ^gf W e s t e r n O n t a r i o
London, O n t a r i o .
1975-1979 B . E . S c . /
o
*
HONOURS AND
AWARDS:
*
*
•
U n iv e rsity o f w estern O ntario
' F a c u lty o f E n g in e e rin g S cience
D e a n 's H onour,-List1
.*
1 9 7 6 , 1 9 7 7 , (L978, 19 7 9 ‘
U■ n.i v e r•s i t y ■ o fr W e■'s t e r r f f Q n f c a r i o F a c u lty o f.E n g in e e rin g S cience
H a r r y C r o s s S i l v e r sM e d a l
1979
1 ■ \
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RELATED WORK
EXPERIENCE:
Research A s s is ta n t
sista n t i
T eaching
o
f
W
e
s
t
e
r
n
O
n
tario
U niversi
1979-198:3
PUBLICATIONS:
( 1 ) ' A.R. W e b s te r and W .I. L ara,! "Microwave a n g l e - o f ~
a r r i v a l m easurem ents u n d e r anom alous t r o p o s p h e r i c
# p ro p a g a tio n c o n d i t i o n s " , A ^nales des
T e l e c o m m u n i c a t i o n s , 3 5 ,' n o i, 1 1 - 1 2 , Nov-Dee 1 9 8 0 .
4
(
2
A . R . W e b s t e r a n d W . I . Lam, " M i c r o w a v e p r o p a g a t i o n
a c r o s s t h e Bay o f F u n d y , I - m a i n p a t h a n g l e - o f a r r i v a l v a r i a t i o n s " , T hird I n t e r n a t i o n a l Conference
o n A n t e n n a s a n d P r o p a g a t i o n (ICAP ' 8 3 ) , IEE a n d URSI,
Apr 1983.
).
*
W . I . Lam a n d A^R. W e b s t e t , " M i c r o w a v e p r o p a g a t i o n
a c r o s s t h e Bay o f F u n d y , I I - m u l t i p a t h - a n g l e s - o f a r r i v ^ l and d e l a y s " , T h ird I n t e r n a t i o n a l C o n feren ce
,o n A n t e n n a s a n d P r o p a g a t i o n . (ICAP 8 3 ) , IEE a n d URSI,
A p r 1.993.
(3)
250
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R e p ro d u c e d w ith p e rm issio n o f th e co p y rig h t o w n er. F u rth e r re p ro d u c tio n p ro h ib ite d w ith o u t p e rm iss io n .
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