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Патент USA US2411564

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Nov, 26, 1946.
' c, B, WAT-rs, JR
2,411,564
COUPLING CIRCUIT
Filed July 4. 7,1942
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INVENTOR
BYG-IESTER
WATTS #2
I
ATTORNEY
Patented Nov. 26, 1946
'
-~_,
I
2,411,564 '
’ UNITEDSTATES PATENT‘ OFFICE
COUPLING CIRCUIT
Chester B.‘ Watts, Jr., East orange, N. _.l'., as
signor to Federal Telephone and Radio Corpo
ration, a corporation of Delaware
Application July 4, 1942, Serial No. 449,828
9 Claims.
(Cl. 178-44)
1
2
This invention relates to coupling circuits and
more particularly to impedance matching trans
formers for. matching dissimilar impedances of
two or more networks.
lengths of the two stub-lines. More particularly,
the short circuited stub-line may comprise two
parallel spaced apart conductors having one end
thereof short circuited and the other end ‘con
nected to a common junction or other point in
'
Several schemes have been proposed heretofore
to match dissimilar impedances such as where
the load impedance of one network is either
higher or lower than the characteristic imped
one of the networksat which impedance match
ing is desired, , Assuming that the adjustable
connection has substantially the same surge im
pcdance as the stub-lines, the length of the short
ance of a transmission line or other network con
necting the load impedance to a source of energy. 10 circuited stub-line may be chosen in the order
One of the most practical schemes for‘impedance '
of a quarter wavelength should a step-up trans
matching heretofore proposed is the adjustable
formation be required, or in the order of a half
short circuited stub-line type of transformer.
Each such stub-line used, however, requires two
adjustments; one being the location of the stub
line with respect to either the maximum or mini
wavelength should a step-down transformation
be desired. If additional lengths are required
15 between the location of the transformers and
mum voltage points of the transmission line, de
pending upon whether step-up or step-down . }
matching is desired,'and the ‘other, an adjust
ment lengthwise of the stub-lineof the short
circuiting conductor thereof. This
type
of
transformer can be used with a fair degree of
the points in the network to which it is to be
connected, additional lengths may be added
thereto in the order of a half wavelength and
multiples thereof, for either quarter wave or
20 half wavelength stubs.
In either a step-up or a step-down transformer,
the open circuited stub-line thereof is taken sub
satisfaction for impedance matching of simple
stantially as a quarter wavelength and may com
networks such as two transmission lines. How
prise two parallel conductors arranged in spaced
ever, when complex network arrangements are 25 relation with respect to the parallel conductors
concerned such, for example, as when aplurality
of the short circuited stub-line. I ?nd that when
of loads are to be matched to a transmission line
the overlap between the two lines, or the dis
having a single source of high frequency energy
tance provided for movement of the adjustable
thereby requiring two or more stub-line trans
connection, is slightly less than a quarterwave
formers, it is exceedingly di?lcult to reach an 30 length, that is to say, about two-tenths of a
impedance balance. This is because each stub
wavelength, more or less, the maximum of the
line has ‘two adjustments, and any network re
reflected waves for all positions of the adjustable
quiring more than one transformer will require
connection occurs at substantially the end of
twice the number of adjustments as there are
the short circuited stub-line towhich a trans
transformers, and since the adjustment of each 35 mission line or other network is connectable.
transformer alters the impedance matching char
The amount of overlap as well as other dimen
acteristics of each of the others, it is almost a
sions of the transformer may be considerably
hopeless task to properly match by means of stub
varied, and the relative dimensions which may
line transformers a complex network system.
be chosen are further described hereinafter.
One of the objects of this invention, there 40
The adjustment of the'transformer is carried
fore, is to provide an impedance matching trans- 7‘
out by providing a movable connection compris
former having but a single adjustment.
Another object of the invention is to provide
an impedance matching transformer which may
be readily arranged for step-up or step-down
impedance matching.
»
Still another object of the invention is'to pro
vide impedance matching transformers vfor ef
ing a pair of conductors conductively connecting
the corresponding conductors of the two stub
lines. This adjustable connection is movable
lengthwise of the stub-lines and as the short
circuited end of one stub-line is varied by such
adjustment, the open circuited end of the other
line is likewise varied but in the inverse relation.
fective impedance matching of a single or plural
It follows, therefore, that the overall effective
load and/or a single or plural source of high 50 length. of the two stub-lines always remains the
‘frequency energy- '
same regardless of the position‘ of the adjustable
The above and other objects of this invention ‘ i connection. When the connection is moved to
I accomplish by combining a short circuited stub
ward ‘the short circuited end of, the one stub, the
line and an ‘open circuited stub-line conductively
impedance correction is increased and when the
connected together by an adjustable connection
connection is moved toward the open end of the
‘so as to vary in inverse relation the e?'ective
.otherstub, the impedance correction is reduced.
2,411,564
3
Since only one adjustment is required by my
improved impedance matching transformer, it is
not only highly satisfactory in matching two dis
similar impedances but may also be used in con
junction with a plurality of loads for connection
to a common source of high frequency current.
Thus, when a plurality of impedance lines or
loads are to be’connected to a common trans
mission line, a separate impedance transformer
24 of the conductors 20 and 2! are connected
through the connecting line H2, £5 to the com
mon junction 33, 3|. The open circuited stub
line of the transformer It! comprises two parallel
spaced apart conductors 25 and 25, the ends 21
and 28 of which are adapted to be connected to
the lines 8' ands of the load I. In some instal
lations the- co'nductors 25 and 25 may comprise
extensions of the transmission line 8, 9.
The two stub-lines may overlap in spaced re
may be provided for each of the loads and since 10
lation for about two-tenths of a wavelength, more
only one adjustment is required for each trans
or less. This overlapping relationship depends on
former, it is a relatively simple matter to adjust
the impedance characteristics of the adjustable
the two or more transformers to reach an im
connection between the two lines and also the
pedance balance at the common junction.
The impedance matching transformer of this 15 length of the distance C. When these relations
are properly chosen the operating results of the
invention is also of particular use for matching a
plurality of sources of energy to a single or a
plurality of loads. The transformer connection
combined stub-lines provides maximum voltage
points at the ends 23, ‘.24 and at points a half
wavelength and multiples of half wavelengths
therefrom along the line Ill, l5.
20
plished by a step-down transformer arrange
The adjustment of the impedance matching
ment wherein the short-circuited stub-line
characteristics of the transformer is effected by
thereof is chosen in the order of a half wave
a movable bracket 35 having two suitably ar
length. In this arrangement the amplitude of
ranged conductors 36 and 31, the conductor 36
the standing waves produced by the transformer
provides a reduction in the impedances at the 25 providing conductive connection. between the
to a plurality of sources of energy may be accom
transformer connection looking in the direction
of the load, a minimum wave point occurring at
the end of the half wavelength line to which the
sources of energy are connected.
conductors 20 and 25 of the two stub-lines and
the conductor 31 providing conductive connec
tion between the conductors 2i and 26. The lo
cation of this conductive connection between the
If more than one load is applied to the trans 30 two lines may be described as dividing the ef
fective lengths of the lines between parts A and
mission line, then, in addition to the step-down
B. The distance A is the distance between the
transformer just described, a step-up trans
conductors of the bracket 35 and the open end
former will be required for each such additional
of the open circuited stub-line and the distance
load. Thus, the plural sources of impedance lines
B is the distance from the conductors of the
may be matched by a single transmission line
bracket 35 to the short circuiting bar 22 of the
and the impedance thereof again matched to a
short circuited stub-line. As the bracket 35 is
plurality of loads.
moved either to the right or left, the distances
For a better understanding of the invention,
A and B will be varied in inverse relation. That
reference may be had to the following detailed
is to say, when the bracket 35 is moved toward
description to be read in conjunction with the
the short circuited conductor 22, the distance B
accompanying drawing, in which,
will be diminished and the distance A will be
Fig. 1 is a schematic illustration of the step
up transformer of my invention applied to a
transmission system coupling a plurality of
loads to a single source of high frequency cur
rent; and
Fig. 2 shows an impedance matching trans
former of my invention of the step-down type
coupling a single load to a plurality of sources
of high frequency current.
Referring to Fig. 1 of the drawing, I have
shown tWo sources of high frequency current 5,
5’ having two transmission lines 6, ‘I and 6’, 1' to
which a plurality of loads Ll‘, L2 and L3 are
adapted to be coupled by transformers If], ll and
i2, respectively. Each load such as Ll may be
connected by means of a transmission line 8, 9,
which preferably is matched to the load, to the
increased proportionally. Conversely, when the
bracket 35 is adjusted in a direction toward the
open end of the open circuited stub-line, the dis
tance A will be decreased and the distance B will
be increased, the overall effective length of the
two stub-lines (that is, A plus B) will always re
main the same. It will, therefore, be clear that
the adjustments of my impedance matching
transformer may be made without changing the
overall effective length of the coupling.
As an illustrative example of the relative di
mensions of av transformer constructed in ac
cordance with my invention, the dimensions in
the following table are those of a transformer
which I caused to be constructed and which was
successfully operated at 110‘ megacycles.
The
dimensions in the table are given with respect to
transformer IE3. Where it is desirable to have a
common junction to the transmission ‘line 6, ‘I at 60 the parts shown in the transformer ill, Fig. 1.
a distance'from the transformer, a connecting
Dimensions of transformers for 110 mc.
line such as M, l5 may be provided in the order
of a half wave or a multiple thereof between the
Diameter of conductors 20, 2|, 25 and
transformer and the common junction. The
26 __________________________ "inches"
transformers l0 and 12 are shown connected by 65
Space X between conductors of each stub
lines each a wavelength long and the transformer
line ________________________ __inches__
H is shown connected by a line a half wavelength
Space
Y between conductors of overlap—
long.
ping lines _______ __'_ _________ "inches"
Since each of the transformers In, H and I2 is
identical to the other, a detailed description of 70 Bars 36 and 31 are rectangular__,___do____
one will sui?ce.
Referring to the transformer ID, the stub-line
thereof comprises a pair of parallel conductors
20 and 21 connected together at one end by a
short circuiting conductor 22. The ends 23 and 75
Length of bars 36 and 31 ________ __-do____
Space between bars 36 and 31 ____ __do____
3/3
13/16
1%
3A6};
21/2
2/32
Overlap of lines (A-l-B) ____wavelength__
0.2
Length of distance C _________ __'___do____
0.05
9,41 15 5.64
5
The tworectangularbars referred to ‘in the
table are. mounted on a'plate made; ofta composi
tion of mica and a phenol‘condensation product
known as “Micalex..f" The; sides: of‘ the bars; are
provided‘ with arcuate grooves ' to“ accommodate
the conductors of the stub-lines with which the
bars have sliding contact.
'
'
6
bracket '55. The open circuited stub-line 54 is
curved like the portion 5| and‘arranged in spaced
opposed relation thereto. The lengths A’, B’, and
C’ correspond to the lengths A, B and C of the
form shown in Fig. 1.
'
By adding to the short circuited stub-line 52
a quarter wavelength of line 53, the minimum
voltage point of the line Will occur substantially
at the junction point 45 and this relationship
While I have found the. foregoing dimensional
relations of the transformer to operate satisfac
tory at 110 megacycles, I wish it understood that 10 renders the operation of the transformer as an
the invention, isrnotzrestricted to these dimen
sional proportions but-that: they may bezconsid
erably varied ‘depending; apparently upon. vari
ance of the impedance, of: certain of" the parts
thereof. For example, a variation‘in the im
pedance of the movable bracket 35 may require a
different
dimensional
relation; between. the
lengths A, B on the one hand and C onthe other
impedance step-down transformation between
the plural'sources of energy and the single load
L4. If desired, an additional length or lengths of
line in the order of a half wavelength or multiple
15 thereof may be inserted between the line section
53 and junction points 45.
'
From the foregoing, it will be clear that a plu
rality of sources of energy may be coupled to a
hand. Also, the overall distance A. plus B. plus C
plurality of loads. In other" words, the loads Ll,
may be greater than a quarter wavelength. It
20 L2, and L3 may be substituted for the load L4 by
will be understood, therefore, that the dimensions
using the same transformer arrangement as il
given for the llil-megacycle transformer are se
lustrated in Fig.v 1 to the right of the junction
lected for purposes of illustration only and- that
points 30, 3|. Such a system will then have a
they may be varieddepending upon the wavee
plurality of sources of energy having a common
length and thestructural shapes and‘ arrange
junction such as 45, a step-down transformer
ments of‘ the parts thereof.
such as 50 coupled in a transmission line between
The transformer It as above described may be '
the junction 45 and the load junction 30, 3| to
adjusted by moving the bracket. 35 so as to effect
which a plurality of loads such as Ll, L2 and L3
the desired wave re?ections and therefore vary
are coupled by step-up transformers I0, I l and I2.
the amplitude of the standing waves in the stub
While two forms of the transformer and two
line to correct the difference between the im
applications thereof are shown and described, it
pedance of the load LI and the source of energy
is recognized that many variations of the two
supplied by the transmission line‘ 6, T. For a
_ forms together with many applications thereof
plurality of loads such as Ll, L2, and L3','indi
are possible without departing from the inven
vidual impedance matching transformers are pro
tion. It will be understood, therefore, that the
vided for the loads and these transformers may
forms herein illustrated and described'are to be
be adjusted by moving the bracket 35‘ of each to
regarded as illustrative of the invention only and
such a position that the combined impedances" of
not as restricting the appended claims.
'
the three parallel loads will balance with ‘the
What I claim is:
characteristic impedance of the transmission line 40
1. An impedance matching transformer for
6, ‘I. Should, for example, each of the loads L1,
connecting together two networks of dissimilar
L2 and L3 be 500 ohms and the characteristic
impedances to selectively control the amount of
impedance of the transmission line be 500 ohms,
energy transferred between said networks while
the parallel loads each should have the appear
maintaining; the impedance matching, compris
ance of 1500 ohms. This may. be effected by 45 ing a short circuited stub-line conductively asso
pro-per adjustment of the brackets 35. of the trans
ciatable with one of said‘ networks, an open cir
formers Iii, H and I2. Should the loads Ll, L2
cuited stub-line conductively associatable with
and L3 be dissimilar, the adjustments of the
the other of said networks, said stub lines being
transformers l9, Hand [2 will then be‘ corre
positioned in overlapping spaced relationship, the
spondingly different, depending, of course, upon ' conductors of said stub lines being disposed to de
the particular impedance of the load associated
?ne the corners of a rectangle lying in a plane
with each transformen
g _
perpendicular to the stub lines with the conduc
In the form shown in Fig. 2 of the drawing, a
tors of each stub line lying in adjacent corners of
plurality of sources of high frequency current 40
said
rectangle, means conductively connecting
and M are shown connected through suitably
the stub-lines together, and said means being
matched transmission lines 42 and 43 to a com
movable to vary in inverse relation the effective
.
' mon junction 45 to which a load L4, which may be
an antenna, is connected‘ by a transmission-line
46, which preferably is matched to the load L4,
and an impedance matching transformer 50 of an 60
impedance step-down type.
‘
The transformer 50 may be arranged for re
ciprocatable adjustment as shown in Fig. 1 or the
adjustment feature may be effected in any ‘other
suitable manner. In Fig. 2, I have chosen to show
the transformer 50 with a rotatable bracket 55.
lengths of the two stub-lines.
‘
2. An impedance matching transformer for
connecting together two networks of dissimilar
impedance to selectively control the amount of
energy transferred between said networkswhile
maintaining the impedance matching, compris
ing a short circuited stub-line conductively as
sociatable with one of said networks, an open
circuited stub-line conductively associatable with
the other of said networks, the two lines being
disposed in overlapping spaced relationship for
The short circuited stub-line 52 has a bracket en
gaging portion 5! thereof curved in the form of an
a distance approaching but not equalling a quar
arc of a circle about .2 wavelength long. This
ter wavelength, means conductively connecting
curved portion is connected by a portion C" the 70 said lines together, and said means being mov
length of which may be varied from about 0.05
able lengthwise of said sections to vary in inverse
to about 0.25 wavelength more or less depend
relation the effective lengths of the two lines.
ing upon the differences, if any, in the surge
3. An impedance matching transformer for
impedance of the conductors of the stub-lines
connecting together two networks of dissimilar
and the conductors of the adjustable connecting " impedance comprising a short circuited stub-line,
12,411,664
7
an open circuited stub-line conductively asso
ciatable with one of said networks, the stub-lines
being disposed in overlapping spaced relation
ship. a line a quarter wavelength connecting the
short circuited stub to the other of said net—
works, means conductively connecting the stub
lines together, and said means being movalle
8
thereof oonnectable to the other of said networks,
the sections being in spaced apart, parallel rela
tion for a portion of a quarter wavelength so
that the four conductors form the corners of a
rectangle lying in a plane perpendicular to the
axis of the sections, with the conductors of each
section being disposed in adjacent corners of the
rectangle so formed, means including a pair of
lengthwise of said lines to vary in inverse rela
conductors conductively connecting the corre
tion the lengths of the two lines.
sponding
conductors of said sections, and said
10
4. An impedance matching transformer for
means being movable lengthwise of said sections
connecting together two networks of
'rnilar
to vary the points of conduction between the cor
impedance to selectively control-the amount of
responding conductors of said sections.
energy transferred between said networks while
"7. A step-up impedance matching transformer
maintaining the impedance matching, compris
for connecting together two networks of dissimilar
15
ing a two-conductor section having one end
impedance comprising a two-conductor section
thereof short circuited and the other end con
in the order of at least a quarter wavelength hav
nectable to one of said networks, a second two
ing
one end thereof short circuited and the other
conductor section having one end open circuited
end connectable to one of said networks, a second
and the other end thereof connectable to the other
two-conductor section having one end open cir
of said networks, the sections being in spaced
cuited and the other end thereof connectable to
apart, parallel relation for at least a portion of
the other of said networks, the sections being in
their lengths with the conductors being dis
spaced apart, parallel relation for about two
posed to de?ne a rectangle in a plane perpendicu
tenths wavelength, and means including a pair
lar to the axis of the conductors and with the
conductors about one twentieth wavelength
conductors of each section lying in adjacent 25 of
conductively connecting the corresponding con
corn rs of the rectangle so formed, means includ
ductors of said sections, and said means being
ing a pair of conductors conductively connecting
movable lengthwise of said sections to vary the
the corresponding conductors of said sections,
points of conduction between the corresponding
said means being movable lengthwise of said
sections to vary the impedance matching chare _
acteristics thereof while maintaining substan
tially constant the combined overall e?ective
lengths of the sections.
5. A step-up impedance matching transformer
for connecting together two networks of dissimilar
impedance to selectively control the amount of
energy transferred between said networks while
maintaining the impedance matching, compris
ing a two-conductor section in the order of a quar
ter wavelength or odd multiple thereof having
one end thereof short circuited and the other end
connectable to one of said networks, a second
two-conductor section in the order of a quarter
wavelength having one end open circuited and
the other end thereof connectable to the other of
said networks, the sections being in spaced apart,
parallel relation for a portion but not all of their
lengths, means including a pair of conductors con
ductively connecting the corresponding conduc
torsof said sections, and said means being mov
able lengthwise of said sections to vary the points
of conduction between the corresponding conduc
tors of said sections.
6. A step-down impedance matching trans
former for connecting together two networks of
dissimilar impedance comprising a two-conduc
tor section in the order of a half wavelength or
multiple thereof having one end thereof short cir
cuited and the other end connectable to one of
said networks, a second two-conductor section
having one end open circuited and the other end
conductors of said sections.
8. In an electrical transmission system having
a plurality of sources of high frequency energy, a
transmission line and a load therefor; the com
bination therewith of a step-down impedance
matching transformer to connect said transmis
sion line to the common junction of said two
sources of energy, said transformer comprising a
two-conductor section connected at one end there
of to said junction and having the other end
thereof short circuited, a second two-conductor
section connected at one end thereof to said load
and having the other end thereof open circuited,
means including a pair of conductors conduc
tively connecting the corresponding conductors
_ of said sections, and said means being movable
lengthwise of said sections.
9, In an electrical transmission system having
a, plurality of sources of high frequency energy,
a plurality of loads and a transmission line to
connect the loads to the common junction of said
sources; the combination therewith of a step
down impedance matching transformer between
said line and said junction and a step-up imped
ance matching transformer for each of said loads,
each of the step-down and step-up transformers
comprising a short circuited stub-line, an open
circuited stub-line, means conductively connect
ing together said lines, said means being movable
to vary in inverse relation the effective lengths
of the two stub-lines.
CHESTER B. WATTS, J R.
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