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Патент USA US2404797

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July 30, 1946.
2,404,797
-w. w. HANSEN
CONCENTRIC LINE MEASURING DEVICE
Filed Dec‘. 12, 1941
2 Sheets-Sheet 1
INVENTOR
WILLIAM w. HANSEN
Y
/
%
His
ATTORN'.‘
I
h\
.
July 30, 1946.
2,404,797
w. w. HANSEN
CONCENTRIC LINE MEASURING DEVICE
Filed Dec. 12, 1941
2 Sheets-Sheet 2
wvob{0km4 "..vQ0O6QO0Q 0
0
.
U
_
.OE 3%meno
INVENTOR
_
WILLIAM W. HANSEN
His A'i’TORNEY
-
Patented July 30, 1946
2,404,797
UNITED STATES PATENT OFFICE
2,404,797
CONCENTRIC LINE MEASURING DEVICE
William W. Hansen, Garden City, N. Y., assignor
to Sperry Gyroscope Company, Inc., Brooklyn,
N. Y., a corporation of New York
Application December 12, 1941, Serial No. 422,716
14 Claims. (Cl. 171-95)
2
1
urement for transmission lines require large sam
ples of test line and give poor accuracy for lines
having small values of attenuation factor and/or
parent from the attached speci?cation, taken in
connection with the accompanying drawings,
wherein one embodiment of the invention is illus
trated.
In the drawings,
Figs. 1A, 1B, and 1C, are longitudinal cross sec
tional views of cooperating portions of the system
power factor.
of Fig. 2.
The present invention is related, generally, to
the art including measuring devices for high fre
quency transmission lines.
Prior art methods of attenuation or loss meas
Furthermore, such methods re
’
Fig. 2 is an elevation view of the system of the
quire measurements to be made and averaged over
a band of frequencies to obtain any satisfactory 10 invention, portions thereof being shown more in
detail in Figs. 1A, 1B and 10.
accuracy. In addition, such measurements rapid
Fig. 3 is an explanatory vector diagram.
ly decrease in accuracy at ultra high frequencies.
Fig. 4 is an explanatory graph.
The present invention provides an apparatus
and methods for performing rapid and accurate
loss and attenuation measurements on extremely 15
short sections of transmission lines and on dielec
tric substances, at ultra high frequencies of the
order of 3 centimeters to one meter in wave
Fig. 5 is an enlarged portion of Fig. 4.
Fig. 6 is a cross section taken along the line 6-6
of Fig. 113.
Fig. '7 is a longitudinal cross sectional view of
an auxiliary device.
Similar characters of reference are used in all
length. Means are provided for efficiently cou
pling the test line to the measuring apparatus and 20 of the above ?gures to indicate corresponding
parts.
for overcoming the e?ects of re?ections at pos
Referring ?rst to Fig. 2, there is shown the
sible discontinuities in the couplings.
complete system of the present invention. A suit
Accordingly, it is an object of the present in
able source 6 of ultra high frequency oscillations
vention to provide improved apparatus and
of a predetermined frequency, which may be in
methods of testing high frequency transmission
lines.
the range from 3 centimeters to one meter in
or adding loss to or loading the line.
1941 in the name of William W. Hansen and
wave length, is coupled to a section of line 68
It is another object of the present invention to
under test, by means of an impedance trans
provide improved apparatus and methods for test
former IA, an exploring and measuring section IB
ing concentric transmission lines of low attenua
tion, at ultra high frequencies of the order of 3 30 ‘and a coupling IC, the latter portions being
shown more in detail in Figs. 1A, 1B and 10, re
to 100 centimeters in wave length.
spectively.
‘
_
It is a further object of the present invention to
Referring now to Fig. 1A, there is illustrated an
provide improved apparatus for exploring an
impedance matching transformer of the type dis
ultra-high frequency standing wave pattern eXist-'
ing on a concentric transmission line without sub_ 35 closed in copending application Serial No. 393,868
for High frequency tube structure, ?led May 17,
stantially altering the ?eld pattern within the line
John R. Woodyard. It is understood that any
other suitable type of impedance transformer may
tion to provide improved apparatus and methods
for accurately and rapidly determining losses in 40 be used here. As has been more fully described in
that application, this impedance transformer IA
small samples of high quality low attenuation
is’ adapted to match an arbitrary concentric
concentric transmission lines and in the dielec
transmission line to one having a particular char
trics thereof at ultra high frequencies, substan
acteristic impedance. In the present instance,
tially independent of reflection effects caused by
connecting the test line to the measuring appara 45 this impedance transformer IA is used to match
the output concentric line 5 of source 6 to the
tus.
measuring line composed of concentric conduc
It is a still further object of the present inven
tors I and 2 and the line 68 under test connected
tion to provide improved approximate methods
thereto by coupling IC. Line 5 is connected to
for rapidly and accurately determining losses in
50 terminals 3, 4, of impedance transformer IA by a
transmission lines and dielectrics.
coupling 8|, which may be similar to coupling
It is yet another object of the present invention
54, shown in Fig. 1C and described below. The
to provide improved coupling devices for concen
line I, 2 is formed to have a particular character
tric transmission lines whereby wave reflections
istic impedance such as 72 ohms.
are minimized.
Other objects and advantages will become ap 55 As has been more fully described in application
It is still another object of the present inven
2,404,797
3
4
Serial No. 3%,868, an impedance match is ob
inner conductor of a concentric line section hav
tained by loosening clamping members 21, 28
and then longitudinally adjusting sliding portion
ing outer conductor 33. This line section is
formed to have a predetermined impedance, such
‘i, 8, 8', l3 and ill of impedance transformer IA
(shown in its rightmost position in Fig. 1A) until
the impedance looking toward the left from sleeve
as 72 ohms.
-
Connected to this line section 40, 33 as by a
T-junction at 38. is a coupling concentric line
section 36, 35 of the same impedance, to which,
as will be described, may be coupled the detect
'5 is a pure resistance. The impedance looking
toward the right from sleeve 1 is also adjusted
ing and indicating apparatus.
or selected to have purely resistive impedance,
The portion of conductor 40 beyond junction
which may be diiierent in value from that look 10
38 is made of small diameter such as at 34, so
ing leftward. These two resistive impedances
that the ratio of the outer diameter of 34 to the
are then matched by rotating sleeve 1 to the
inner diameter of 33 is large. Furthermore, a
proper angular position, where the quarter wave
shorting plug 31 is inserted at the end of line
line enclosed by sleeve ‘I has an impedance equal
to the geometric mean of the two resistive im 15 section 33, 34 at .such a position that the stub
line 33, 33 is exactly one-quarter of a wave length
pedances to be matched. The function of the
at the operating-frequency of source 6, so that
transformer IA is thus to match source 6 to the
the line section 33, 34 will offer a very high im
portion of the device in which actual measure
pedance. Plug 31 may be made adjustable in a
ment is accomplished, which will now be de
scribed.
20 manner well known to the art, if the frequency
range of source 6 'is to be varied.- The position
As‘ seen in Figs. 1B and 1C, conductors I and 2
of probe III] relative to conductors I and 2 may
extend through the remainder of the measuring
be determined by means of a stationary scale 64
device. Insulators l2, I3, I4, and i5 provide sup
port for and position conductor i concentrically
and an index ?xed to sleeve 20, as shown in
'
in conductor 2. The entire device is supported 25 Fig. 2.
Adjacent to slot 32 and fastened to inner con
from a base Q5 by supporting posts 41, 48, 49.
ductor 2 is a sector 4| of tubing positioned con
Referring now particularly to Fig. 13, con
centric with conductor 2, as shown in Figs. 1B
ductor i has slidably mounted thereon a short
and 6. The function of sector 4| is to compen
sleeve It which carries, by means of threads
sate for the change in impedance due to the
thereon, a clamp ll’. Rotation of clamp I'I rela
presence of slot '32, and thereby prevent mis
tive to sleeve 55 causes a tapered portion I8 of
match and undesired Wave reflections.‘ The
clamp I‘! to bear on tapered ?ngers I9 of sleeve
probe 40 is extended toward sector 4i, thus act
I 6, thereby clamping sleeve IE5 at any desired
ing as a capacitative probe for exploration of
longitudinal position on conductor I. At a suit
able distance irom short sliding sleeve I6 is a 35 the region along the length of sector 4|. Probe
40 is positioned’ ‘as vfar away from sector M as
long tube 23, also slidably mounted on conduc
possible, consistent with obtaining reasonable
tor 8. Tube 29 has a threaded portion 2| at its
end adjacent to sleeve I6 and carries on this
values of output to be measured, so as not to
threaded portion H a threaded ‘flange 22.
disturb appreciably the ?eld pattern between'
conductors I, 2.
Mounted concentrically with conductors I and 2
on ?ange 22 is a tubular member 23 extending
Referring now to Fig. 1C, ?xed outer tubular
conductor I extends ‘past the end of ‘movable
toward sleeve I6. This member 23 carries a hear
ing ring 24, in which are rotatably or ?xedly
sleeve 20, and is'supported near‘its 'end by leg
mounted a plurality of hardened steel balls 25,
49, ?xed to vbase '45. The concentric line elements
which bear against a hardened bearing plate 26
I, 2 are ended in such a' manner that a concentric
?xed to sleeve I 6. Sleeves I3 and 2B are urged
transmission line 68 in which losses are to be
together by means of one or more springs 31
measured may be suitably joined thereto. As
shown in the ?gure, inner conductor 2 is prefer;
Whose ends are fastened to rings 29 and 3|] ?xed
respectively to the adjacent ends of sleeves I6
‘ably terminated a suitable distance inside outer
and 20.
_
' .50 conductor I, and the end of conductor 2 is bored
Member 23 is normally adjusted so that springs
or made hollow as at 50. If the line 58 to be
3I are under tension. Then rotation of member
measured has conductors of ‘the same diameters
23 will serve to change slightly the separation
as those of line I, 2, directcoupling is made by
of sleeves I3 and 2D, with springs 3i serving
forming the end of the inner conductor of - line
to take up and eliminate any back lash in 55 168 in the same manner as ‘conductor 2.
threads 25.
outer conductors are ‘juxtaposed as at 62, and a
connecting sleeve 54 is suitably ?xed to both outer
Also ?xed to sleeve 23 is a suitable rack 42,
engaged by a pinion i3 journaled in a support
conductors, as by a squeeze or soldered jointing
44 ?xed to base 33. In this Way, upon loosening
or by suitable threads, not shown. The inner
clamp I l, rotation of knob 65 connected to pinion 60 sconductors are joined by a connecting member
43 will serve to longitudinally position both
5|, formed to have a central portion of diameter
sleeve 20 and sleeve l6 along conductor I in a
equal to the outer‘ diameter of the inner con
coarse manner. Then, upon tightening clamp
ductors and of length equal to the separation
I‘! and rotating member 23, a ?ne and accurate
between the inner conductors when the outer
adjustment of sleeve 20 may be obtained, without
conductors are joined. The outside sections‘of
backlash.
connecting member 5| have a diameter equal
Outer tubular conductor I is provided with an
to the bores of the inner conductors, and are
elongated longitudinal slot 32 parallel to inner
squeezed into these bores. Thus, a smooth‘ joint
conductor 2. Extending through slot 32 and ?xed
is formed relatively free from undesirable dis-'
to outer tube 28 by means of collar 85 and set
continuities and wave re?ections.
screw 86 is a coaxial line device which serves
If the two lines to be joined are of different
as the terminal and exploring apparatus by
sizes, the coupling device '58 of Fig. 1C may be '
means of which actual voltages appearing inside
used. Into the centrally placed hole 50 in the
of ‘conductor I may be measured. This device
end of conductor 2 is inserted the-member 5|,
consists of an exploring electrode 43 forming the 75 which may be as just described; withla- portion
2,404,797
5
of diameter equal to the outer diameter of con
ductor 2 and two portions 52 and 53 of diameter
equal to the hole in conductor 2. Over the outer
conductor I may be placed concentric sleeve 54.
The adapter then consists of an inner conductor
55 of outer diameter equal to that of member
standing wave pattern along conductors i‘, 2,
and, as is well-known in the art, the ratio of
voltages at minimum and maximum points in this
pattern is given by:
=tanh aL
R
5! and conductor 2, and made to slide over por
tion 53 of member 5|, and a tapered portion 56
connected to conductor 55 and tapering to a por
The variation of voltage along line I, 2 is shown
in Fig. 4.
Readings proportional to the values Vmin2 and
tion 51 of diameter matching that of the bore of 10
Vmax2 may be obtained by ‘observing readings of
the inner conductor 69 of the line 68 to be meas
the galvanometer 61 as the probe 46 is moved
ured. The outer conductor of the adapter con
along the measuring device by means of rack 42
sists of tubular member 58, haVing inner and
and pinion 43 or by means of the screw 2| and
outer diameters equal to that of tubular conduc
tor I, and having a tapered portion 60 tapering 15 nut 23, as described. In this way B2 may be
obtained directly, leading to the value of u by
to diameters also matching those of the outer
a simple calculation, L being known.
conductor of the line 88 to be examined. Con
Several approximations may be used for re
ductors 51, 66 may then be connected to line 68
stricted conditions. Thus, where all is very small,
in the same manner as conductors I, 2 were con
nected to 55, 58, or in any other suitable manner 20 tanh 0114 nearly equals ozL, and there is obtained
the approximate formula
which will provide a smooth re?ectior'iless joint.
Conductor '55 is positioned within conductor
@gé?
58 by means of an insulator 6|. Corresponding
(aL)2<<l
max
(la)
faces 81, 88 of insulators I5, 6| are spaced apart
If all is large,
a distance electrically equal to one quarter wave 25
V in
1—'6—2“L
__
length, including the effect of the dielectric mate
vj;=l—+mgl —2e 2"!’
rial of the insulator thickness. Similar insulator
arrangements may be used at the joint between
and
adapter 56 and test line 68. Any other suitable
type of joint may be here used.
1
_ V...x
(lb)
Referring now to Fig. 2, there is shown, con
—-aLg2 10gt ————~2
nected to concentric line coupling member 35, 36,
The above method offers several practical dif
a crystal detector 65, which is preferably of the
ficulties. If uL is large, then
"cat’s whisker” type mounted in a plastic insulat
ing material, provided with suitable distributed
Vmin
by-pass capacitance for by-passing the energy
V1118!
of the operating frequency and provided with
is nearly unity, since the re?ected wave is very
suitable leads 66 for applying the detected cur
highly attenuated. Hence, the quantity in pa
rent to a galvanometer 61 of proper range. As
is well known, for low values of high frequency 40 rentheses in (1b) is hard to determine with suffi
cient accuracy.
voltage, the reading of galvanometer 61 will be
proportional to the square of the high frequency
If 11L is very small,
[1 Vmin]
voltage input.
Vmiu
The method of using the apparatus will now be
V1113!
described. Two situations arise: (1) where the 45
is
very
small,
and
it
is
difficult to obtain a suit
characteristic impedance of test line 68 is the
able detector which will maintain a regular law,
same as that of conductors I, 2; and (2) where
such as the square law, which it approximates
these impedances differ.
closely for small values of input, over a widely
Let it be assumed, ?rst, that the characteristic
impedance of the concentric transmission line 50 varying range of inputs. .As a practical matter,
aL should lie in the range .1<aL<l for best re
68 to be measured is the same as the section of
sults with the above method. This means that
line I, 2 of the measuring device containing probe
for high quality lines. where a may be of the
46. In this case, there will be no discontinuity
order of 10-3 inrl, fairly long lengths of test
in impedance at the junction 62 between the two
line must be used.
lines. For simplicity, let it also be assumed that
Another method of using the device of the
the attenuation in the part of the line containing
present invention may be understood by the fol
probe 46 is negligible, at least in comparison to
lowing analysis.
that of line 68. This is a reasonable assumption.
Let V1 represent, for a given position of probe
because of the relatively short length of line I, 2
to the right of probe 40, and also because of the 60 40, the magnitude of the forward (left to right)
travelling wave, and furthermore, let V1 be of
high quality with which line I, 2 may be con
unit length. This means that all vectors to be
structed, for measuring purposes
Upon impressing a high frequency voltage from
source 6 upon the system, a wave will run from
left to right in the measuring device. If the
length of the test line is L, the voltage of this
wave will be attenuated by a factor £41’ in trav
elling to the end of line 68, where or is the well
used are referred to V1 as a base, and all mag
nitudes are relative to that of V1. The re?ected
wave may be represented as a vector V2 having
magnitude 6-2“.
If the probe 40 is at a position
corresponding to a minimum of the curve of
Fig. 4, then vector V2 will be in line with and
opposing vector V1. At a maximum point of the
known symbol for attenuation constant of line 68,
and is the quantity to be measured. With line 68 70 curve of Fig. 4, V2 will be in line with and addi
tive to V1. For some other position, V2 will be at
short-circuited at its far end, the wave is re?ected
at the end of line 68, and a return wave travels
some phase 0 with respect to V1, as shown in
back toward probe 40. The total attenuation of
the re?ected wave will then be FM’. The waves
running in the two opposite directions form a
Fig. 3.
The resultant voltage indicated by the
device will then be Va.
'
As probe 48 moves along conductors I, 2, it will
2,404,797
7
8
be clear that@ will vary, and VR, will seem to ro
presence of waves re?ected from the joint. Both
methods may be used at once, a joining section
tate about the terminus of vector V1. Now, for
small values of 0:11, corresponding to short lengths
56, 59 already described being used to avoid such
of high quality and low attenuation line, the
length e_2“L of vector V2 is approximately given by
reel-2.115 '
discontinuities as far as possible.
For re?ection compensation, the far re?ecting
end of the test line 68 is now not short-circuited
(2)
but is connected to a shorted line section of small
but variable length, which may be constructed
By the usual cosine law of trigonometry,
the manner shown in Fig. 7.
VR=x/(1)2+(l—2aL)Z—2(l=2aL) (cos 0) (3) 10" in The
far end of line 68 is attached to conduc
But, for small values of 0,
cos 0%1 -%2
tors 10, ‘H, which expand, keeping the same di
ameter ratio, to conductors 12, 13, by means of
tapered portions 19, 80. Slidably mounted in
(4)
side tubular conductor 12 is a conducting tube
15 14, whose end is tapered as at 82 to provide a
Hence, using these approximations,
magi/0W
<5)
smooth transition between tubes 12 and 14. In
ner conductor 13 has a central bore 76, which is’
neglecting second order terms.
slidably engaged by a conductor 15. Conductors
‘l5 and ‘M are rigidly fastened and electrically
moved by probe 40, as follows:
20 ‘connected by a shorting disk 78. Conductor 13
41m:
is also provided with a smooth tapered transition
=T
<6)
section 83.
With the device of Fig. 7 attached to the re
Where A is the operating wave length of source 6,
?eeting end of the test line 68, variation of the
and :c is measured from a minimum point, as
shown in Fig. 4. In this way, Equation 5 becomes 25 length of the device Will vary the phase of the
wave re?ected from disk 18 back into test line
68, and thus varies the phase of the re?ected
wave at probe 49 with respect to that of the for
ward wave.
The shape of this curve near the minimum at
If Z2 is the characteristic impedance of line
zn=0 is shown enlarged in Fig. 5. The width or
68, then the impedance seen looking in the direc
sharpness of the minimum depends on ocL, and
The angle 0 may be related to the distance m
tion of line 68 from junction 62 will have a min
imum value of Z2 tanh aL or a maximum
may be used to determine a1: and thereby cc.
Thus at the minimum, where x=0, and .
Z2
tanh aL
according as the phase of the reflected Wave is in
and this is the minimum indication on galvanom
phase opposition or in aiding phase with respect
eter 61.
to the forward Wave.
If $0 is the value of a: for which the
galvanometer reading is double its minimum 40
If the impedance of the measuring line I, 2 is
denoted by Z1, then the corresponding standing
wave ratios will be
Z1
Z1 tanh all
z2 tanh aL or
from Equation 8. Hence, from the above, it will
be seen that the distance are required to move the
probe 40 from a minimum value of Va2 to a posi
or their reciprocals.
Four possible conditions arise, as follows:
tion giving twice the minimum value of VR2 is
determined by:
QL=Z§E for aL<<1
(10)
60"
This method of measurement uses crystal cur
3. Z1>Z2 and
rents over a small range, so that deviations from
square law operation of the crystal are mini
mized. Furthermore, absolute calibrations of the 551
galvanometer 61 are unnecessary.
In this Way,
a practical and accurate method of measuring
small attenuations is provided. The value we may
be taken as the measure of the width of the
60
standing Wave minimum.
The above method was derived on the basis of
negligible re?ections from the junction of the
test line 68 to the measuring apparatus. If con
siderable mismatch exists, it may readily be seen
that inaccurate results Will be obtained. For ex
ample, with a very long line, whereby no re?ect
ed Wave is obtained, “L should be measured as
in?nite. However, mismatch or impedance ~dis~
continuity at the joint will cause a portion of
4. z,>z2 and aq?j
In the ?rst case, both the minimum and maxi
mum impedance exhibited by the test line 68 are
greater than that of the measuring line I, 2, and
the test line 68 accordingly exhibits open cir
cuit properties to the measuring line. This means
that the position of the voltage minima on meas—
uring line I , 2, as determined by probe 40, will not.
change as the effective length of the test line 58
is varied by moving the adjustable section ‘M, 75
of its termination. In this case the maximum
and minimum standing wave ratios are as in (11).
In the second case, the impedance of meas
uring line I, 2 lies between the minimum and
maximum impedances of test line 58. Accord- I
the outgoing wave to be re?ected, yielding stand 70 ingly, test line 68 will exhibit short-circuit prop
erties for some values and open-circuit proper
ing waves in the measuring device, which would
ties for other values. Therefore, the position. of .
then give inaccurate results.
the voltage minimum will jump by a quarter
This trouble can be handled in two Ways: either
Wave length as the line 68 is varied from mini
by taking care to make the joint free from im
pedance discontinuities, or by allowing for the 76. mum to maximum impedance. The minimum
2,404,797
1. In a method of determining attenuation and
like loss factor characteristics of a transmission
given'by
Z? tanZh (0L) and Z1 tanZh (aL)
10
What is claimed is:
and maximum standing wave ratios are now
(12)
line, the steps of coupling said line with a source
In the third case, the impedance Z1 of the
to produce standing waves along said line,
measuring the wave amplitude in the vicinity of
the standing wave minimum for determining the
width of the standing wave minimum wherein
said wave amplitude changes by a predetermined
function, said width of the standing wave mini
l
2
of electrical energy of known wavelength so as
measuring line I, 2 is greater than the maximum
impedance of line 68, so that line 68 exhibits a
short-circuited property and the minima remains
?xed.
The standing wave ratios are here
z1 tanh
Z2 (aL) an d Z2 tanh
Z1
(13)
mum being a de?nite function of the attenua
tion characteristics of said line, and utilizing said
width for determining the attenuation per unit
Finally, in the fourth case, again Z1 lies be
tween the limits of the impedance of line 68, 15 length of said transmission line.
2. The method of measuring transmission line
which therefore may exhibit both short-circuit
attenuation and like loss factor characteristics
and open-circuit properties, causing the minima
comprising the steps of projecting a forward
to change as the length of the shorting section
wave along said line, reflecting said wave from
of Fig. '7 is varied. The standing wave ratios are
20 the far end of said line, whereby a standing wave
here
pattern is set up at the sending end of said line,
Z tanh (aL)
Z2 tanh (aL)
varying the phase of said re?ected wave to obtain
(14)
Z2
and
Z1
predetermined relation with respect to said for
ward Wave, and measuring the maximum and
If the minimum standing wave ratio is denoted
by R1 and the maximum by R2, then it will be 2.5 minimum standing wave ratios at said sending
end, said characteristics being determined inde
clear that, if the position of R1 is the same as
pendently of re?ections at the sending end of said
R2, (cases 1 and 3)
line as a function of said ratios.
tanh (01L)
(15)
3. Apparatus for exploring the voltage along
30 a concentric line having an axial opening in the
If R1 and R2 are at different positions (cases 2
and 4)
tanh (aL) = vRlRg
(16)
outer conductor thereof, comprising a probe,
means for moving said probe along said opening,
means for preventing energy leakage through
said opening, and means connected to the inner
Accordingly, the above analysis gives the fol- 1
lowing test procedure: measure the standing
conductor of said line for compensating for the
change in impedance of said line due to said
opening.
wave ratio for varying settings of the short-cir
cuit section of Fig. '7. If the test line is perfectly
matched to the measuring device, the ratio will
be independent of the variable line length, and
4. Apparatus as in claim 3 wherein said last
named means comprises an axially extending
sector of a cylindrical tube superposed on the
inner conductor of said line opposite said open
the attenuation may be determined from (1) or
(10).
mg.
If the standing wave ratio does depend on line
length, the minimum and maximum ratios are
determined and the attenuation may be derived
a concentric line having an axial opening in the
outer conductor thereof, comprising a probe, a
5. Apparatus for exploring the voltage along
sleeve enclosing said outer conductor, means for
mounting said probe in said sleeve to project
through said opening, means for moving said
sleeve relative to said line whereby said probe
from (15) or (16), whichever is applicable.
The $0 method derived above also holds for the
mis-matched case. Here
tanh (aL)=
95%
9302
(17)
60 is moved along said line, and means connected
to the inner conductor of said line for compen
sating for the change in impedance of said line
due to said opening.
6. Apparatus for exploring the voltage along a
concentric line having an axial opening in the
outer conductor thereof, comprising a probe, a
sleeve enclosing said outer conductor, means for
mounting said probe in said sleeve to project
if the minima are stationary, and
tanh (aL)=g)':‘r\/Iol $02
(18)
if they move.
The methods described above are not restricted
to the measurement of attenuation of concentric
transmission lines. The present invention is
equally adapted for measuring power loss or
power factor of dielectric materials, as by making
a ?xed type of line and inserting various dielectric
through said opening to be capacitively coupled
GU
materials or beads.
Furthermore, the present invention may be
used with open transmission lines, by providing
suitable adapting connectors between the test
line and the measuring device.
to the inner conductor of said line, means for
moving said sleeve relative to said line whereby
said probe explores different sections of said line,
means for indicating the voltage picked up by
said probe, and means connected to the inner
' conductor of said line for compensating for the
change in impedance of said line due to said
opening,
7. Apparatus for exploring the voltage along a
As many changes could be made in the above
concentric line having an axially extending open
construction and many apparently widely differ
ent embodiments of this invention could be made 70 ing in the outer conductor thereof, comprising
a probe, a sleeve enclosing said outer conductor,
without departing from the scope thereof, it is
intended that all matter contained in the above
description or shown in the accompanying draw
ings shall be interpreted as illustrative and not
in a. limiting sense.
75
means for mounting said probe in said sleeve to
project through said opening to be capacitively
coupled to the inner conductor of said line, means
for moving said sleeve relative to said line, where~
11
12
by said probe explores different sections of said
with said rackwhereby said sleeve may be moved
line, said sleeve moving means comprising coarse
moving means including a rack ?xed to said
along said line section by rotation of said pinion,
and ?ne adjustment means including a bearing
°
sleeve and cooperating with a ?xedly pivoted
plate member movable axially along said line
pinion, and ?ne moving means including a co
axial threaded member cooperating with a ?xed
section, means for anchoring said member to said
line section, and means cooperating with said
bearing plate and engaging a coaxial threaded
member and having threads engaging said
portion of said sleeve; and means for indicating
threaded sleeve whereby ?ne movement of said
the voltage picked up by said probe.
sleeve may be effected by anchoring said member
8. Concentric line apparatus comprising a con v10 to said line section and rotating said threaded
centric transmission line having an axially ex
means.
tending opening in the outer conductor thereof,
12. In a method of measuring attenuation and
an electrically conductive sleeve surrounding said
like loss factor characteristics of a transmission
line and opening and having an inner radius
line, the steps of coupling said line with a source
substantially equal to the outer radius of said 15 of electrical energy of known wavelength‘so as
line, and means connected to the inner con
to produce standing waves along said line,
ductor of said line opposite said opening and
measuring the wave amplitude at the position of
extending substantially the length thereof for
the standing wave minimum, and measuring the
compensating for the change in impedance of said
distance from said position to the nearest point
. line due to said opening.
.20 at which the square of the wave amplitude is
9. Concentric line apparatus comprising a sec
double the square of the amplitude at said po
tion of concentric transmission line having an
sition, said distance being a de?nite function of
opening in the outer conductor thereof, and
the desired characteristics of said line.
means connected to the inner conductor of said
13. Coaxial line apparatus comprising a sec
line for compensating for the change in im 25 tion of coaxial transmission line having an open
pedance of said line due to said opening, wherein
ing in the outer conductor thereof, and means
said last-named means comprises an axially ex
connected to the inner conductor of said line for
tending conductive member connected to said
compensating for the change in impedance of
inner conductor opposite said opening.
said line due to said opening, said last named
10. Concentric line apparatus comprising a 30 means comprising a body attached to said inner
section of concentric transmission line, a slidable
conductor opposite said opening and extending
sleeve surrounding the outer conductor of said
axially therealong by an extent substantially
line, and means for moving said sleeve relative
equal to the axial extent of said opening.
to said line, said last-named means comprising
14. A method of measuring attenuation and
coarse moving means including a rack ?xed to 35 like loss factor characteristics of a transmission
said sleeve and cooperating with a ?xedly piv
line sample, comprising the steps of conducting
oted pinion, and ?ne moving means comprising
radio frequency energy of known wavelength to
a coaxial threaded member cooperating with a
said line sample through a low-loss energy con
bearing plate and engaging a coaxial threaded
ductor, measuring the Wave amplitude in the
portion of said sleeve.
40 vicinity of a standing wave minimum in said
11. Electrical apparatus comprising a section
conductor for determining the width of the
of coaxial line having an inner conductor and a
standing wave minimum wherein said wave am
coaxial outer conductor, a slidable threaded
plitude changes by a predetermined function,
sleeve surrounding the outer conductor of said
and utilizing said width for determining the at
line, coarse adjustment means including a rack 45 tenuation per unit length of said transmission
?xed to said sleeve and a pinion ?xedly pivoted
line sample.
with respect to said line section for cooperation
WILLIAM W. HANSEN.
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