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Sept. 24, 1946.
w D. o. GRIEG
2,408,061
STABLE PULSE GENERATOR
_ Filed Dec. 20, 1941
17/6” VOLMGE'
-
BY
- DOA/ALP a 6/?76'6'
_
.
‘Am
,
Patented Sept. 24, 1946
2,408,061
UNITED" STATES PATENT OFFICE
2,408,061
STABLE PULSE GENERATOR
Donald D. Grieg, New York, N. Y.,‘ assignor to
Federal Telephone and Radio Corporation, a
corporation of Delaware
Application December 20, 1941, Serial No. 423,862
2 Claims. (Cl. 250——'36)
This invention relates to improved means for
the generation of short impulses of relatively high
energy and periodically recurrent.
It is an object of the invention to provide rel
atively simple means for the generation of im
pulse energy.
Another object is to provide an improved sta
bilized impulse generator wherein it is not nec
2
of tube T1 to produce a sinusoidally varying volt
age of the form shown in Fig. 2a.
The remaining elements of tube T1 preferably
form an ampli?er for amplifying portions of the
voltage generated by the above—described oscil
lator. Preferably, in accordance with the in
vention, the suppressor grid of tube T1, which
forms an effective control grid for the ampli
essary to synchronize the generator to an ex
?er, is biassed below cutoff so that class C oper
ternal frequency standard.
A further ebject is to provide an improved 10 ation of the ampli?er results. It will be clear
that the output of tube T1 will then comprise a
impulse generator wherein the impulse frequency
series of current surges or pulses, the duration’
is independent of load or supply-voltage varia
tions.
of which is determined by the degree to which
the ampli?er portion of tube T1 is operated class
It is also an object to provide an improved im
pulse generator wherein the impulse width is 15 C, that is, the magnitude of negative bias ap
constant over a range of supply voltage or load
conditions.
plied to the suppressor grid across the used por
tion of resistance Rs. Preferably, this bias is
relatively great so that only very short current
A still further object is to provide an improved
surges are derived in the output of tube T1. These
impulse generator wherein the impulse recur
rence frequency may be varied and the width 20 current surges may be of the form shown in
Fig. 2b.
of impulses at the same time maintained con
In. accordance with features of the invention,
stant in spite of such frequency variation.
Other objects and further features of novelty _ the output of tube T1 is applied directly across
an inductance L2. Now, when the above-men
and invention will hereinafter be pointed out
or will become apparent from a reading of the 25 tioned short pulses of current ?ow through in~
ductance L2, voltage surges of high value may
following speci?cation in conjunction with the
appear thereacross, as will be clear. Inasmuch
drawing included herewith. In said drawing,
as there is unavoidably some capacity associated
Fig. 1 is a schematic diagram of a circuit in
with inductance L2 and its associated circuit, the
corporating features of the invention, and Fig. 2
illustrates graphically the progressive treatment 30 nature of the voltage pulses appearing across
L2‘ will be damped oscillations, as shown for ex
of wave forms in the circuit of Fig. 1.
ample, in Fig. 2c.
Broadly speaking, the invention contemplates
‘
Now, in order to obtain relatively high voltage
pulses of short duration from these damped os-“t
regularly recurrent current surges across an in
ductance whereby correspondingly recurrent 35 cillations, I propose to use appropriate shaping
means for eliminating all of the voltage varia
damped oscillations are set up in the circuit of
tions but the initial surge associated with these
the inductance. Appropriate shaping means
pulses. Several methods for so shaping the out
thereafter serve to remove all of such oscilla
put appearing across inductance L2 will naturally
tions but the first current surge thereof.
40 occur to those skilled in the art. For example,
Speci?cally, and in accordance with the pre
it would be possible to shunt inductance L2 with
ferred form shown in Fig. 1, an oscillator feeds
resistance, thereby increasing the damping and
an electron-coupled device to supply the reg
further reducing any effect of the undesired volt
ularly recurrent current ‘surges. In the form
age variations. The objection to this method is
shown, the circuit of this oscillator includes a 45 that the. initial pulse is likewise considerably
vacuum tube T1 of known form having a cath
reduced in amplitude, and at the same time its
ode, control grid, screen grid, suppressor grid, and
width at the base is substantially broadened due
the generation of impulse energy by applying
anode. The oscillatory circuit further comprises
the parallel impedance combination of an in
ductance L1, a variable capacitance C1, and an
other capacitance C2. The frequency of oscil
lation of this circuit is largely determined by
the magnitudes of elements L1, C1 and C2, and
this frequency may be de?ned as
to the effect of such a shunt resistor on the time
50
constant of the damped oscillation circuit.
In accordance with thejinvention, however, I
propose to employ thermionic damping means
shunted across inductance L2 in order to remove
the undesired voltage variations following the
55 initial pulse.
In the form shown, a diode T2 is
connected across inductance L2, and a resistor
R3 is preferably in series therewith to reduce the
effect of the plate-cathode capacitance of the
diode. The operation of such a connection will
In operation the oscillator functions with the
screen grid, control grid, and. cathode circuits 60 be readily apparent. Assuming the initial pulse
across inductance Le to be positive, the cathode
2,408,061
3
.
of diode T2 will be positive with respect to the
plate thereof. No current will then ?ow through
the diode, and the ‘diode shunting e?ect will be
grid bias resistor R1, variation of supply voltage‘
will change the suppressor voltage proportionally,
since these voltages are obtained across a common
supply resistance. Thus, for any variations in
these voltages, s bstantially constant pulse width
tion immediately following the initial pulse, diode
will result. It follows that the circuit described
T2 will be conductive, thus effectively shunting
is capable of generating stable pulses without
inductance L2. The removal of a voltage surge
any necessity of synchronization, as by external
across inductance L2 in this manner immedi
monitoring circuits. The circuit obviously has
ately removes any cause for ,further and lesser
the added advantage of simplicity of operation.
voltage variations, It follows, therefore, that only 10
AlthoughI have described my invention in par
single pulses corresponding to the initial surge
ticular detail'in connection with the preferred
of voltage across inductance L2 will appear across
form shown, it is to be understood that many ,
inductance L2 when diode T2 is connectedas
modi?cations may be made fully within the scope
shown. It is to be noted that in the preferred
. thereof. For example, if it is not desired to have
form of eliminating the undesired voltage surges,
a flexible variation of impulse frequencies, a crys
the amplitude of the initial surge is not noticeably
tal oscillator may be employedinstead of the
affected, and successive lesser surges are com
oscillator described. Such an oscillator would, of
pletely eliminated.
course, furnish a permanently reliable and stable
Inasmuch as the width of pulse generated in
pulse frequency,
'
.
the above manner depends upon the damped os
Furthermore, time modulation of the pulses
cillation frequency, any desired control over such
generated bythe circuit described may be ob
width (within limits, of course) may be effected
tainedby the relatively ‘simple expedient of vary
by varying a circuit constant within the damped
ing some circuit constant in the damped oscilla
oscillation circuit. For example, inductance L2
tion circuit in accordance with ‘an intelligence
negligible. During the negative cycle of oscilla
' may be controllable in any known manner as in
- dicated by therarrow traversing this element.
- signal.
,Such modulation may be effected in a
relatively simple manner, say by varying thelin
ductance of L2 in accordance with the intelli
gence signaLlas will :be clear.
Appropriate output may be derived from the
, above-described circuit by well known means. In
the form shown, a so—called cathode follower
VWhat I claim is:
'
ampli?er circuit is employed. This ampli?er cir
V 1. Pulse'generator comprising, in combination,
cuit includes a vacuum tube device T3, and the
a vacuum tube having control elements includ
ing an anode, a cathode and a grid, and a high
output pulses may be obtained therefrom in a
load P1 across a low magnitude resistor R4 in the
internal plate resistance characteristic, a tank
cathode, ‘circuit of tube T3. In the form shown,
circuit, means interconnecting said tank circuit
35
a coupling condenser C3 in the input circuit of
with elements of said vacuum tube to produce
tube T3 is preferably made small in order to re
oscillations therein, an output circuit connected
duce the shunting effect of the input to tube T3,
between the vanode and cathode of said tube,
and a grid resistor R2 is also small in order not
to increase the width of pulses due to the above
noted undesirable damping effect of excessive re
sistance.
It will be noted in connection with the pulse
generator described that since the pulse frequency
isdetermined solely by the sinusoidal oscillator
frequency, the frequency of pulse output may be
varied by appropriate control of the oscillator, as
by varying condenser C1, for example. The am
pli?er and oscillator sections of tube T1 are iso
lated from each other with the exception of a
coupling by the electron stream in this tube. It
means biasing an element of said vacuum tube
40
, value relatively small compared with the internal
resistance of said tube, alum-directional recti?er
- connected in shunt with said inductive reactor,
means deriving induced voltage pulses from said
reactor when said current surges from said vac
uum tube are impressed thereon, and means to
produce the maximum voltage pulses possible
from the time duration of the applied current
surges, comprising means varying the bias of the
vacuum tube element and means varying the tun
follows that the pulse generator will have the
desirable feature that variation in load output
may not affect the pulse frequency. Furthermore,
in accordance with well known methods, the oscil
. ing of saidreactor.
lator may be made to supply a frequency sub
stantially independent of supply voltage by proper
adjustment of the cathode tap on inductacne L1
and adjustment of the screen grid voltage by po
tentiometer R1.
to sucha value as to produce periodically recur
rent currentsurges in said output circuit, a tun;
able inductive reactor serially connected in said
output circuit, said reactor having a resistance
For any ?xed value of control A -
2. The combination according to claim 1, ‘in
whichsaid ‘vacuum tube includes a suppressor
‘grid, and said biasing means includes means for
varying the bias on said suppressor grid.
'
DONALD D. GRIEG.
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