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Dec. 10, 1946.
Filed June_ 23, 1943
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Patented Dec. 10, 1946
George H.- Brown, Princeton, N. J., a‘s'sig'nor t0v
Radio Corporation of America, a corporation of
Application June 23, 1943, Serial No. 491,963
3 Claims. (Cl. 2‘50—13)
The invention covered herein may be manu-j
factured and used by or for‘ the Government of
the United States‘ for‘ governmental, military,
of signal energy .to the receiver. When the trans‘
mitter is operating‘, the‘ tube discharges, sub-'
st'antially'short circuiting the open end of the
line, so that the inductive reactance of the line
naval and national defense purposes without
payment to me or‘ assigns of any royalty thereon. in is effectively connected across the receiver input.
In order to present a su?ici'ently low impedance
This invention relates to radio frequency dis
at this point, an intermediate point on the line‘,
tribution systems, and more particularly to net‘
rather than the open end, is connected‘ to the
works for operating a radio transmitter and a re
receiver. Thus, by “tapping down” on the‘ line,
ceiver with a common antenna system. In cer
tain applications, particularly those in which 10 the minimum impedance is lowered, at the ex
signals comprising short pulses are radiated,
pense' of loweringthe' maximum impedanceby
reflected by a remote object and picked up‘ at or
near the location of the transmitter, ity is desir
able to‘ use a single‘ antenna system rather than
provide separate antennas" for reception and ‘
the same ratio.
transmission. In‘ order to prevent damage to the
receiver during the periods of transmission, as
circuited end. ‘ In a typical installation, an error
well as dissipation of power, it is necessary to
provide means for isolating electricallyi'the re
This in itself is not a particu
larly serious defect. Howevenzth'e adjustment of
the line length becomes morev and more critical
as the tapping point is‘ moved toward the short
of one percent in the adjustment may render
the system inoperative, owing tov failure to pro;
test the receiver or because of improper loading
of the transmitter, or both.
ceiver from the transmitter.
According to the present invention, a radio
Prior art systems for this purpose have been
transmitter l is connected through a coaxial
somewhat uncertain in operation, extremely crit
line 3 to an antenna system 4. A receiver 5 is
ical of adjustment, and relatively ine?icient in
connected through a coaxial line 1 to a point 9.
that a compromise must be effected between the
degree of isolation of the receiver and the amount 25 on the transmitter line 3. A section I | of coaxial
line is connected to the receiver line 1 at a point
of transmitter power dissipated in the network.
l3, 1A wave length distant from the junction
It is the principal object of the present inven
point 9. The line H is 1A.; wave length long. A
tion to provide an improved radio frequency net
short circuited stub line I5 is also connected to
work for operating a transmitter and a receiver
30 the point l3. A line H, 1/4 wave length long,
with a common antenna system.
is connected to the transmitter line 3 at a point
Another object is to provide an improved net
IS, 1A; wave length nearer the transmitter than
work of the described type which incorporates no
the point 9. A half wave open-circuited line 2|
moving parts and provides substantially instan
is connected to the end of the line IT. A
taneous switching of the antenna from trans
35 short circuited stub 23 is also connected to the
mitter to receiver.
end of the line H. Non-linear impedance devices,
A further object is to provide an improved net
such as gaseous discharge tubes 25 and 21, are
work of the described type which is efficient, not
connected across the open circuited ends of the
critical of adjustment, and capable of providing
lines H and 2| respectively.
substantially complete isolation of the receiver
from the transmitter without absorbing appre 40 The operation of the above described system is
ciable power.
as follows:
A typical automatic transmit-receive switching
system according to prior practice involves the
the half wave line H as substantially a short
When the transmitter I is operating, relatively
These and other objects will become apparent
high peak voltages are impressed on the gas
to those skilled in the art upon consideration of
tubes 25 and 21, causing the gas to ionize so that
the following description, with reference to the
accompanying drawing, which is a schematic 45 the tubes present relatively low impedances
across the open ends of the lines I I and 2|. The
diagram of a transmission network embodying
low impedance of the tube 2| is reflected through
the invention.
circuit across the line ‘| at the point I3. The low
use of a parallel-resonant transmission line con 50 impedance at the point I3 is re?ected through
the quarter wave section on the line 1 as a high
nected to the input of the receiver. The line is
impedance at the point 9. Thus the major por
short circuited at one end, and a glow discharge
tion of the energy reaching the point 9 from the
tube is connected across the other end. When
transmitter l ?ows past the pointy 9 to the
the tube is not discharging, the parallel resonant
impedance of the line has no effect on the ?ow 55 antenna. Similarly, the low impedance presented
by the tube 21 is re?ected as an open circuit
to the point l9.
During the periods when the transmitter I is
not operating, the tubes 25 and 21 are non
conductive, presenting very high impedances at
the open ends of the lines H and 2|.
The stubs
I5 and :23 are, adjusted to parallel resonate the
reactances presented'by the tubes ‘25 and’ 2''!
through the lines H and 2| at the points l3
I claim as my invention:
'1. A radio frequency switching system includ—
ing a ?rst transmission line for connectionbe
tween a transmitter and an antenna system, a
second transmission line connected to a point
intermediate the ends of said ?rst transmission
line ,for connection to a receiver, a third trans
mission line 1Ay'wave vlength longg'connected to
said ?rst transmission line at a point 1A; wave.
and 3|. The open circuit point 3| is re?ected as
a short circuit at the point I9 through the
quarter wave line I1. .The short circuit atthe
point I9 is re?ected as an open circuit at the
10.7, length distant from the point of connection of
point 9. Energy traveling down the line 3 from
transmission line 1/2 wave lengthlong connected
said second transmission line thereto, a fourth
transmission line 1/2 wave length long connected -'
to the end of said third transmission line, a ?fth
the antenna ?ows into the line 1 to the receiver 15 to said second transmission line at a point 1A
5. The open circuit presented by the line II at
wave length distant from the point of connection
the point l3 has no effect upon the ?ow of,’
betweensaid ?rst and second lines,,and gaseous
energy through the line 1. The lengths of the
discharge tubes connected to the ends of said
various line sections are not unduly critical and
fourth and ?fth transmission lines.
adjustments may be made by actual measure 20
2. A radio system including a transmitter, a
ments of length, without causing substantial de
receiver and an antenna system, a main trans
parture from ideal performance;
mission line connected between said transmitter
Thus the invention has been described as an
and said antenna system, a branch transmission
improved distribution network for radio fre
line connected between said receiver and a point
quency systems employing a common antenna 25 on said main transmission line, a quarter wave
transmission line connected to a Point on' said
charge tubes are connected through line sections
main line 1A wave length nearer said transmit
fortransmission and‘ reception. Gaseous dis
of resonant lengths to lines connecting the an
ter than the point of connection of said branch
tenna j with the receiver and the transmitter.
line thereto, half wave open-ended line sections
During transmission, the gas in the tubes is 30 connected to the end of said quarter wave line
ionized, rendering the tubes conductive and
thereby providing relatively low impedances
and to a point on said branch line 1%; wave length '
distant. from the point of connectionrof said
branch line to said main line respectively, and
gaseous discharge tubes connected to the open
which are re?ected inthe transmission line cir
cuit to divert the ?ow of energy from the receiver
to the transmitter. During reception, the gas 35 ends of said half wave line. '
tubes are non-conductive, presenting relatively
3. The invention as s'etv forth in claim 2, in
high impedances which are re?ected to the trans
cluding short-circuited stub lines connected to
mission line circuit to e?ectiv'ely connect the re
the points of connection of said half wave lines
ceiver to the antenna system and disconnect the
to said branch line and said quartervwave line;
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