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Патент USA US2406839

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Sept 3,1946-
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E. LABINV Em
‘
2,406,839
_ IMPEDAN‘CE‘MATCHING DEVICE
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Filed Jan. 12, 1942
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INVENTOR.
5/14/45 4145/”
BY
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MES m #76‘
l
ATTORNEY.
2,406,839
Patented Sept. 3, 1946
UNITED STATES PATENT OFFICE
2,406,839
IMPEDANCE MATCHING DEVICE
Emile Labin, New York, and James H. Nye”
Jackson Heights, N. Y., assignors to Federal
Telephone and Radio Corporation, a corpora
tion of Delaware
Application January 12, 1942, Serial No. 426,455
4 Claims. (Cl. 250-17)
2
This invention relates to an improved form
of impedance matching arrangement and in par
ticular to means for adjustably matching the
apparent input impedance of a radio frequency
oscillator to the output impedance of a modulator
feeding the oscillator.
The. invention contemplates particular appli
cation in the case of impulse modulators and
transmitters of the nature disclosed in the co
age of the output, as clearly set forth in the said
application. Synchronization of impulses pro
duced by this apparatus across inductance L2
may be effected by applying relatively low volt
age negative pulses to the grids of modulator
tubes 10 and II through a blocking condenser
I1. As pointed out in the said application, a
resistor 18 may be connected across the terminal
of grid coil L1 in order to limit the negative grid
pending‘applica-tion of Emile Labin, Serial No. 10 impulses to the desired value without changing
the maximum voltage obtainable across the plate .
406,499, ?led August 12, 1941, and entitled “Pulse
coil L2 and substantially to eliminate oscillations
transmitters.” These devices are particularly
in the grid circuit-thus assuring regularity of
adaptable to radio locator equipment.
vIt is an object of the invention to provide an
improved form of impedance matching device.
Another object is to provide relatively simple
the pulsing cycle.
‘
In the form shown the radio frequency oscile
lator includes two triodes I9, 20 connected in
push-pull. The ?lament, grid, and plate cir
cuits of tubes l9 and 20 are tuned by balanced
to give maximum output when supplied with high
line structures 2|, 22, and 23, respectively, each
voltage impulse energy.
Other objects and various further features of 20. of which is adjustably tuned by a short-circuiting
member 24, 25, or 26, as the case may be. As
novelty and invention will hereinafter be pointed
shown input is supplied from across inductance
out or will become apparent from a reading of
L2 in the modulator to short circuiting member
the following speci?cation in conjunction with
26 of the radio frequency oscillator plate cir
the drawing included herewith.
cuit, and output may be derived from an induc
The said drawing depicts schematically an im
tive coupling 21 with the plate tuned circuit 23.
pulse modulator and radio frequency oscillator
means for adjusting a‘radio frequency oscillator
Now in order to obtain maximum output from
circuit embodying features of the invention.
the modulator-oscillator circuit shown it is clear
As disclosed in the said copending application,
that the output impedance of the modulator
high voltage pulses of short duration may be
generated from a relatively low D. C. voltage in 30 (looking back across inductance L2) should equal
or substantially approximate the apparent input
somewhat the following manner. The basic cir
impedance of the radio frequency oscillator
cuit involved includes a relaxation oscillator
(looking into the oscillator from inductance L2).
having inductive feedback and an R. C. time con;
Inasmuch as the band of frequencies necessary
stant circuit in the ?lament return. Operation
faithfully to transmit impulse energy is rather
depends upon establishinga high current in a
large, it is preferable that this impedance be
coil in the plate circuit of the relaxation oscil
essentially resistive so as to be substantially in
lator and rapidly interrupting this current. The
dependent of frequency. The magnitude of this
resultant discharge of the coil into the load pre
resistance R should correspond to the critical
sented by a radio frequency oscillator may then
develop a peak voltage which is on the order of L10 damping resistance of‘ coil L2, as de?ned by the
?ve times the magnitude of voltage applied to the
relaxation oscillator.
relation
‘
e
In forms shown in the
said application it is this large voltage which
serves as plate supply for the radio frequency
oscillator. I
.
Referring more in particular to the drawing,
the impulse generator or modulator includes a
where C represents the total stray capacitance
in parallel with inductance L2, and L is the in
ductance looking into L2.
,
Now, due to the fact that the energy passing
pair of triodes I0, I I having all circuits connected
from the modulator to the oscillator is so inter
in parallel, an inductance L2 in the plate circuit
inductively coupled through a coil L1 to the input 50 mittent and transient in nature, it is extremely
difficult to design the oscillator to have the de
sired input impedance R for the duration of an
impulse. Practically then, it is necessary to de
sign the oscillator to present this impedance R
age, as impressed between terminals 15 and [6,
may be on the order of one ?fth the peak volt 55 for what are considered to be average conditions,
or control grid circuit, and resistance and ca
pacitance time constant elements [2, l3, and I4
across the input circuit. The plate supply volt
2,406,839
3
and to provide some means for adjusting the os—
cillator in actual operation.
This subsequent adjustment of the oscillator
may be effected by controlling the bias of oscil
lator tubes l9 and 20, as by varying the grid bias
resistor 28. However, in the particular applica~
tion contemplated tubes l9 and 2'9, have abnor
mally large ?laments for relatively high emis
sion during the periods of transmitting impulses,
i. e. when the radio frequency oscillator is in OS‘
cillation. In this type tube it is well known that
the grid characteristic is of an extremely criti
cal nature with respect to bias variation for
optimum oscillation conditions. As a practical
matter therefor the magnitude of resistor 28 is
relatively small so that the bias may be relatively
stable—thus permitting use of the desired grid
characteristic.
4
form shown, it is to be understood, of course, that
many modi?cations, additions, and omissions
may be made without departing from the spirit
and scope of this invention.
What we claim is:
1. In an impulse transmitter comprising an im
pulse modulator feeding a radiof'requency oscil
lator having vacuum tube means including cath
ode, grid, and anode circuits and a substantially
resistive impedance in the anode-cathode circuit,
the method of matching the impedance of the os
cillator to that of the modulator which comprises
varyingsaid impedance in the anode-cathode cir
cuit until- maximum output is obtained from the
oscillator.
2. man impulse transmitter comprising an im
pulse modulator feeding a radio frequency oscil
lator having vacuum tube means including a cath
Now, in accordance with the invention it is pos
ode circuit, a grid circuit, and an anode circuit,
sible to change the apparent impedance of the 0s 20 the output of said modulator being in said anode
cillator without making any appreciable change
circuit, and said cathode circuit having resistance
in- grid bias. It is-proposed that such adjustment‘
therein, the method of obtaining. maximum out‘
be made by variation of an additional resistance
put from the oscillator which comprises adjust
29in the cathode circuits of oscillator tubes {9'
ablyv varying said resistance, whereby the appar
and 20. Since resistor 29 is in eifect inv both the 25 ent impedance of said anode circuit may be varied‘
plate and cathode circuits of tubes l9 and 29, a
Without appreciably changing. conditions in said
slight variation thereof may have the’ effect of»
grid circuit.
altering plate circuit impedance to a relatively
3. An impulse transmitter comprising an im
large degree vwhile negligibly changing grid‘ bias.
pulse generator and a radio frequency oscillator,
It has been. found that the increase in output '3 said generator including a Vacuum tube having
gained from varying resistance 29‘ to match- the
an electron emissive electrode, a control elec
oscillator impedance to that of the modulator is
trode, and an electron receiving electrode, an in
far greater than any losses or other undesired
eifects obtained from the slight. change in grid
bias occasioned by adjustment of resistor 29.
It is to be' noted that it is. the A. C. impedance
in thecathode circuits that‘ determines the decay
ductance, a source of energy, means connecting
said source and saidinductance in series between
said receiving electrode and another electrode. of
said tube, a coupling coil inductively‘ coupled. to
said inductance, a timing circuit, and means com
shape of- the pulses transmitted. This impedance
necting saidcoil and said circuit in series between
may comprise either capacitance inv parallel with
said control electrode and said emissive electrode,
resistor 29 or inductance iniseries therewith; For 40 said oscillator including vacuum tube means in
steep-walled pulses it is accordingly considered’
cluding a cathode circuit, a grid‘ circuit, and an
preferable that precaution be taken that capaci
anode circuit, said anode circuit being. coupled
tance in. parallel with. resistor 29» is as small as
across said inductance, said grid circuit including
possible. Furthermore, it is. to be noted that
biassing means, and said cathode circuit‘ includ
since resistor 291is in the output circuit its mag-.. . ; ing relatively high emission cathode means and
nitude should. be kepta'slow as possible‘t'o: ensure
adjustable resistance means.
maximum power output and‘ minimum power loss
4. An impulse transmitter comprising an im
in this resistor.
pulse mcdulator and a- radio frequency oscillator,
Although in the above description element 29"
said oscillator including vacuum tube means hav
has repeatedly been referred to as a‘ resistance, .
it is to be considered as an impedance having
substantially resistive characteristics
It will be seen that we haveset forth a. rela
tively simple method for matching the- imped
ance of a pulse modulator to aradiofrequency os- ' .
cillator after these devices. have been. built and
set up. The proposed. method enables ready ad»
justment. for optimum oscillation should tubes be
replaced or operating frequency be changed.
Whilewe have described our invention in consid
erable detail in connection with the preferred
ing an anode circuit to ground, a cathode circuit
to' ground, a, grid circuit to ground, and means
coupling said anode’ circuit to said modulator,
said grid circuit having a biasing resistance
means, said cathode circuit having an adjustable
resistance means adjustment of which operates
to vary the" impedance of the anode circuit. for
impedance matching with respect to the modu
lator impedance while negligibly affecting the
grid biasing adjustment.
EIVH‘LE LABIN.
JAMES H. NYE.
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