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Патент USA US2405314

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Aug. , 146.,
Filed June 9, 1945
Patented Aug. 6, 1946
Robert W. Masters, Erlton, N. J., assignor to Ra
clio Corporation of America, a corporation of
Application June 9, 1943, Serial No". 490,379
2 Claims. (Cl. 178-114)
This invention relates generally to high fre
the higher frequency signals through the input
coupling circuit and balanced transmission line
quency transmission networks and more particu
larly to a transmission network for relatively
to the output circuit and the load. One terminal
of a lower frequency transmitter is connected to
the common terminal of the output quarter wave
tuned lines. The remaining terminal of the lower
isolating a plurality of generators of diñerent fre
quencies which are coupled to a common load cir
' Networks of the type described have wide utility
in radio transmitter antenna circuits wherein a
frequency transmitter is grounded. The shielding
means on the output two conductor line is also
plurality of transmitters having different output
frequencies are coupled through a common trans
mission line to either common or adjacently dis
posed antennas.
Brie?y, the instant invention comprises means
whereby two transmitters having the same or dif
It will be seen that both terminals of the low
frequency transmitter are substantially at ground
potentialwith respect to the higher frequency sig
nals, and coupling of the lower frequency signal
source to the higher frequency transmitter is slub
ferent output frequencies are coupled to a 15 stantially limited by the balanced connection to
balanced transmission line in a manner which
the balanced transmission line and the relatively
provides satisfactory transmission of both fre
high capacitive reactances intermediate thereof.
quencies to a load circuit connected to the trans
mission line, while eifectively isolating the trans
'Thebalanoed shielde'dV line comprises the two con
ductors for the higher frequency output connec
mitters from each other. If the feeder line from 20 tion to the load, while both of the output line
the higher frequency transmitter is not already
conductors taken together and the grounded
shield comprises the output connection from the
lower frequency transmitter to, for example, a
second load.
Essentially, the shunt connected tuned lines
may be considered as reactances for providing
suitable impedance matches between the balanced
of the balanced line, while the remaining terminal
transmission line, the load circuit and the sepa
is grounded.
rate transmitter feeder lines. In order to mini
The balanced transmission line includes sepa 30 mize re?ections in the feeder line from the higher
rate capacitors in series with each of the con
frequency transmitter, the input impedance of
ductors thereof. A center tapped tuned circuit
the balanced line should be substantially resistive
such as, for example, two parallel disposed quarter
and equal to the surge impedance Z'O of the higher
wave conductors, is connected across the balanced
frequency feeder line. The ?rst tuned reactor
line intermediate the capacitors and the higher ' X2., the second tuned reactor Xe and the two
balanced With respect to ground, it may be
coupled to the balanced transmission line through
any conventional coupling circuit such as, for
example, a resonant re-entrant network of the
type illustrated herein. One terminal of the
second transmitter is coupled to both conductors
frequency input coupling circuit.
The remote
ends of the quarter wave lines are grounded and
a shorting bar between the quarter wave lines
may be employed for adjusting the circuit to be
non-receptive to the higher transmitter fre
quency. A shielded two wire transmission line is
connected between the output terminals of the
balanced transmission line and a load device such
as, for example, an antenna.
A second pair of parallel disposed quarter wave
conductors are connected together at the ends
remote from the balanced line and also connected
across the balanced line intermediate the series
capacitors and the output terminals. A second
shorting bar may be provided for tuning the
series capacitors Xb should therefore be adjusted
to bear the following relations:
where the output impedance Zz of the balanced
line is substantially resistive and equal to the
load resistance Rz.
It will therefore be seen that by proper choice
of the sizes and signs of the reactances Xe, Xb and
Xe, any resistive output impedance Zz maybe
transformed ef?ciently With any predetermined
combination of balanced line, series capacitors,
input resistance R1.
and tuned quarter wave lines comprises a 'n- net
If, however, the output impedance Zz is not
work which insures satisfactory transmission of 55 purely resistive, but includes some reactive com
second pair of quarter wave conductors to anti
resonance at the higher output frequency. The
ponent, the shunt reactance element Xc of the
and grounded at one end thereof. The remain
ing ends of the quarter wave conductors ll), |'|
are connected to different conductors of the bal
anced transmission line 4 intermediate the ca
pacitors 5, 6 and the re-entrant network 3. A
circuit may be calculated to a value, in excess of
the value provided by Formula 3, which would
precisely parallel-resonate the reactance of the
load impedance Zz, thus providing an effective
shorting bar l2 is connected between the quarter
wave conductors Ill, ll for tuning the circuit to
offer high impedance to the- currents of the out
load of pure resistance.
Since the load impedance Zz varies as a func
tion of frequency, it is essential that both react
put frequency of the high frequency transmit
ances Xz, and Xe be adjustable in order to satisfåT
the requirements of Equations 21 and 3. The react 10 ter I.
A second pair of parallel disposed conductors
ançes of the series capacitors Xb are made large
L3, VhLhaving, for example, lengths of the order
enough so that, even though ?xed, equation (1)
of any cdd multiple of 1A wave length at the op
is always satis?ed. It should be understood that
the variable reactors X8, Xe may;be inthe form
erating frequency of the high frequency trans
of tuned parallel conductors as illustrated here- '
mitterl, are connected together, and are also con
nected to thedifferent conductors of the balanced
`transn'iission line 4 at points intermediate the
in, or in the case of lower frequency transmission
circuits, in the form of lumpedltuned reactors of
conventional types.
capacitors 5, 6 and the output terminals 1, 8, re
spectively. A second shorting bar 15 is connected
between the second. parallel disposed conductors
E3, lê'for tuning the circuit to offer high imped
ance to the currents of the frequency of the high
frequency transmitter. The common terminal of
the second pair of tuned parallel conductors |3,
It should be understood that either the higher
or the lower frequency transmitter may be con
nected to the feeder line which is balanced with
respect to ground and also that the system will be
operable with transmitters of substantially'the
same output frequencies. Likewise, the system
is 'applicable to transmission of any frequencies
M is :connected'to one output vterminal of a lower
whatever, if suitable circuit componentsare?se
lected 'for the particular Operating frequency
frequency transmitter 15. The remaining output
terminal of the lower frequency transmitter IB is
Theshield l'l of the two Wire shielded output
Among the objects of the invention are to:pro
vide an improved methodof and means forccou.` 30 line ~9 is grounded. The two conductors of the
two wire ouputline 9 are connected to a ?rst load
pling a plurality of generators having .different
device or antenna Hš. A neutral point IS on the
output frequencies to a common Vtransmission
?rst load device 1B is connected to one terminal
line in v'a manner which e?ectively isolates the
of a second load or antenna '20. The remaining
generators from each other. Another 'object of
terminal of the second load or antenna 20 is con
the invention isto provide an improved method
nected to the shicld ll of the two Wire shielded
of andmeans for connecting two generators hav
line 9. The particular type of load device or an
ing different output lfrequencics to a -balanced
tenna system employed does not comprise any
transmission network connected to'a common
par-t of applicant's invention, and it should'be
transmission line whereby satísfactory transmis
understood that any known means may beem
sion of both vfrequencies may be accomplished
while effectively isolating the generators'from 'ployed for connecting the two conductors and
Shield of the two fwire shielded transmission line
each other. A further object of the invention "is
Sato one or more load devices.
to provide an improved circuit for Vcouplinga plu_
It will be seen `that the resonant re-entrant net
rality' of generators having different output »fre
work 3, the balanced transmission line 4 and the
quencies through a ar network to `a common out
two conductors of the shielded transmission line
put transmission line. An additional object of 'the
9 provide an e?icient coupling'circuit between the
invention is to provide an improved circuit ?for
higher frequency transmitter l and the ?rst load
coupling two generators having _different output
device l8l Since the two pairs of tuned parallel
frequencies to a Vbalanced transmission `ocircuit
disposed lines IB, H and IS, IQ, respectively, offer
high impedance to the currents of the higher
frequency transmitter I, the connection of the
connected to a _common output transmission line'
wherein circuits offering high impedance Vto the
currents of the vhigher frequency c permit Fsatis
lower frequency transmitter IG to the common
connection of the second pair of tuned lines is
factory coupling of the lower frequency transmit
ter to the balanced transmission line.
The invention will be described in further de- “
tail by Vreference to' the accompanying vdrawing ;of
which the single ?gure'thereof is a vschematic cir
cuit diagram of a preferred embodiment.
Referring to the drawing, -a high frequency
radio transmitter l having an output concentric 60
line 2 is connected through a resonant re-entrant
network 3 of the 'type commonly known as a
"bazooka” or “line .coupling transformer." A
transmission line 4, balanced with respect to
ground, is connected to the output terminals of
the resonant re-entrant network 3.
Series ca
pacitors 5,.`6 are inserted in each of the conduc
tors of the balanced transmission line Ã. The out
put terminals 1, ~8 ofV the balanced transmission
line vll are connected to the conductors of a '
shieldedtwo wiretransmission line-9. A pair of
eifectively isolated from the higher frequency
transmission circuit. Similarly, the ungrounded
connection of the low frequency transmitter' I 6 to
the common connection of the second pair of
tuned lines 13, 64 provides a dual path through
the conductors |3', M and the two conductors of
the shielded output line 9 to the second load de
vice 28. The low frequency transmitter is there
foreeifectively isolated fromthe high frequency
transmitter since the low frequency connection is
> substantially at ground potential with respect to
the high frequency transmitter, and the series ca
pacitors 5, G offer a high impedance path to the
lower frequency energy.
Thus the invention described comprises an im
proved method of and means for coupling two
generators having different output frequencies to
conductors IG, H, having, for example, lengths of
a balanced 1r network for transmitting energy
the order of slightly in excess of any odd multiple
of 1A wave length at the frequency of the high
from both generators to a common output line
while effectively isolating the generators from
frequency transmitter, are connectedV together 75 eachother.
I claim as my invention:
1. A circuit for relatively isolating two gen
erators of different frequencies, said generators
erators having different output frequencies, said
being coupled to a common transmission line, in
cluding a balanced transmission line, means for
connecting said higher frequency generator to
sion line including balanced means for connecting UK said line, a first balanced tuned'circuit having a
grounded neutral point connected across said
said line to a source of high frequency oscilla
tions, second balanced means for connecting said
line, a second balanced tuned circuit connected
line to a source of relatively lower frequency os
across said line, capacitors serially inserted in the
cillations, means for making said high frequency
conductors of said line intermediate said ?rst and
connections at points on said line at balanced po
said second tuned circuit connecti/onsV thereto,
tential with respect to said lower frequency gen
means for connecting' one terminal of said lower
erator, means including capacitors serially con
frequency generator to the neutral point in said
nected in said line for making said lower fre
second balanced tuned circuit, means for coupling
quency connections at second points on said line
said balanced line to a load circuit balanced with
substantially at ground potential for said higher
respect to ground, and means grounding the re
frequency generator and means for connecting
maining terminal of said lower frequency'gen
said line to a load device.
2. A circuit for relatively isolating two gen
generators being coupled to a common transmis
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