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Патент USA US2409621

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Patented I@cla 22, 1946
2,409,620
UNITED STATES PATENT »oi-‘FICE
OSCILLATION GENERATOR
Walter W. Fritschi, Manhasset, N. Y., assignor to
Bell Telephone Laboratories, Incorporated,` New
York, N. Y., a corporation of New York
Application January 17, 1942, Serial No. 427,131
7 Claims. (Cl. Z50-«36)
2
This invention relates tol oscillators and par
ticularly to vacuum tube oscillation generators
of the feedback type.
The invention has for its object the provision
.
is obtained when the oscillator is designed to sat
isfactorily regulate the amplitude ofthe voltage
of the signaling frequency; and ,
of a simple, single vacuum tube oscillator adapted
Fig. 3 shows the envelope shape when insuiii-`
cient voltage regulation is provided.
>The oscillator shown in Fig. 1 of the drawing
D
to supply signaling current of a desired frequency
interrupted at a desired rate, and the production
of sufficient output power `'in 'such an oscillator
with the amplitude ratios desired and with sat
isfactory limits of voltage and frequency varia
tion under variable load conditions.
comprises a vacuum tube Ill, a feedback resistor
I9, a variable condenser 2l), an induction coil
vacuum tube oscillator designed to simultaneously
comprising windings 2l and 22, a potentiometer
comprising resistor 23 and brush 24, an induction
coil comprising windings 3|, 32 and 33, impedance
element 35, condensers 35 and 3l', a potentiometer
comprising resistor 38 and brush 39„ an output
transformer Ml, and output terminals 4I and 42.
The tube I0 is of the screen grid high amplifica
tion type having a thermionic cathode I5, control
grid Id, screen grid I3, anode II, and a pair of
produce oscillations at the signaling frequency
electron beam conñning plates I2, positioned be
This invention is an oscillator comprising a
single vacuum tube arranged to produce oscilla
tions of a desired signaling frequency and to
interrupt the signaling frequency at a desired
rate.
A feature of the invention is a single
and‘at the rate of interruption desired, the- ratio
tween the anode I I and screen grid I3. Reference
between the amplitudes of the twoy frequencies 20 may be had to the> patent to Ol. H. Shade No.
>being adjusted so that the feedback of the lower
2,107,520, granted February 8,`1938„for a detailed
frequencyv alternately drives’ theV grid potential
description of a‘tube lof the preferred structure
into a range wherein the amplification is insuiñ
cient to sustain oscillation at the higher frequency
and character. The ‘cathode I5 is indirectly
heated by a heating element I6 in usual manner,
and the beam deflecting plates l2 are electrically
connected to the‘cathode. While the tube’shown
is o‘f the beam type, a high amplification tube
without beam deiiecting plates maybe used. >The
anodef‘cathode space current circuit is traced
from anode I! through winding 2l of oneinduc
tion coil, through winding 3| and a partof wind
ing 32 of the other `induction coil, brush‘ 30, and
through battery 50 to the cathode I5. The con
denser 36 is bridged across the windings 3l, 32
and `33 to form a tuned network which is resonantL
to the desired signaling frequency, fory instance
and into a range wherein oscillation .at the higher
frequency is sustained.A Oscillation at the lower
frequency is sustained by the inertia'of its tuned
circuit and the higher, signaling frequency is
thereby effectively interrupted at the rate of the
lower frequency of oscillation.
30
Other features of the invention are the pro
vision of volume limiting means in such an oscil
lator and the provision of a shunt, having a nega
tive impedance-voltage coefficient, across the net~ >
work which is tuned to the signaling frequency
to obtain a more constant amplitudeoi ‘the sig
naling frequency.
‘
35
l000"cycle's'per`second; and the variable conf`
_
A clear and complete understanding of the
denser 2D‘is bridged across the winding 2I to form
altuned network which is resonant at the fre
quency at which.À it Yis desired that the signaling
invention will be facilitated‘by a.' description of ‘
the oscillator illustrated schematically inA the
drawing, in which oscillator the invention fand
frequency’be interrupted, for instance 15 cyclesV
per second. Condenser 2B is variable torpermit
adjustment of its capacity to tune the condenser
and ‘Winding 2l -to the desired interrupting fre
its various features are embodied. The invention
is not limited to the specific arrangement shown,
various modifications being possible within the
scope of the invention.
45 quency. „ The
`
Referring to the drawing which consistsof
three figures,
` '
n
Fig. 1 shows an oscillationgenerator compris
ing a single vacuum ‘tube lI0 arranged to generate
oscillations of La desiredsignaling frequency and
to generate oscillations of a desired interrupting
frequency at which the oscillations of the signal
ing‘frequency are interrupted;'
p
,
_A
„
,
‘ Fig. 2 shows an oscillogram V'of the output of
control `grid-cathode circuit is
traced from grid I4 through resistor I9,- tolpoten
tiorneter brush 24, through> resistor 23 in parallel
with winding 22„thence to potentiometer'brush Y.
50
39, through resistor`38 to cathode I5. The control
grid" is not biased byía direct current` source <and
~ bothfthe signaling frequency andthe interrupting
frequency are fed back tol the controlgrid; thel.
`amount of feedback being dependent `upon the
adjustment of‘lbrushes 2li and `3i). The resistor
the oscillator shown in Fig. 1; thi's'envelope shape 55 I9- has a high resistance to'limit the grid circuit.
'2,409,620
3
4
The primary winding of output transformer 40 is
bridged across the winding 3l and an impedance
and the grid potential again builds up to and be
yond the cut-off point, the signaling frequency
element 35 having a negative temperature-voltage
coefficient, is bridged across the winding 33 and
reappears. Thus in either case, that is with zero
grid bias or with a negative grid bias, the sig
a part of the winding 32 as determined by the Oi naling frequency voltage is stopped and started
at the interrupting frequency and substantially
position of brush 34 to limit the amplitude of the
complete suppression of the signaling frequency
oscillations of the signaling frequency. The ele
is obtained during one half-cycle of the voltage of
ment 35~may consist of silicon carbide of such
the interrupting frequency.
dimension and character as to provide the desired
The oscillograms shown in Figs. 2 and 3 indi
range of impedance. By adjustment of brush 35
cate that the envelope shape of the signaling fre
the portion of induction coil winding 32 which
quency may be regulated by the character of the
is included in the anode-cathode circuit may be
negative-impedance element 35, a satisfactory
varied and by adjustment of brush 34 the amount
envelope being illustrated in Fig. 2 and an un
of inductance which is shunted by element 35
satisfactory envelope resulting from insufficient
may be varied. The condenser 3l, which is in
regulation on the part of element 35 being illus
series with potentiometer resistor 38, is effective
trated in Fig. 3. These two oscillograms illustrate
to prevent direct current through the resistor.
the range of envelope shapes which it is possible
Assume that the feedback potentiometers have
to obtain through control of the amplitudes of the
been adjusted to obtain the desired feedback po
tentials and that the oscillator is placed in op 20 two frequencies of oscillation by the element 35
and the amount of attenuation in the feedback
eration, for instance, by the closing of the bat
paths. There is, of course, a limit to this regu
tery connections. Immediately, both of the
lating action and the envelope shape shown in
tuned 'circuits begin to build up» oscillations at a
Fig. 3 illustrates a case where there is insufñcient
very high rate, the initial impedance of element
35 being high. As the impedance of element 35 25 regulation and the signaling voltage is entirely
eliminated when the grid potential decreases to
decreases, the feedback decreases until a point of
or beyond the cut-off value.
stability is reached. `rI‘hereafter the element 35
The useful output voltage may be obtained by
tends to` compensate for any changes which af
directly connecting the load to the terminals lll
fect the amplitude of oscillation, for instance,
changes in load, battery Voltage and, within 30 and 42; or if greater output or better regulation
is required, an intermediate amplifier may be
limits, the amplification provided by the tube. A
provided. The effective length of each period of
similar impedance element may be connected
signaling frequency oscillation is slightly less than
across winding 2i to compensate for such changes
the length of the positive half cycle of the inter
in amplitude of the oscillations at the interrupt
ing‘frequency. Although it is believed to be pre 35 rupting frequency due to a change in frequency
during the build-up and decay of the signaling
ferable to operate the oscillator with zero grid
voltage. The effective duration of the signaling
bias„as shown in the drawing, satisfactory op
voltage is illustrated in Fig. 2.
eration is obtained by providing a negative grid
The advantages of the above-described oscil
bias,> inlconventional manner. With zero grid
bias,'the signaling frequency is interrupted dur 40 lator over known methods of generating a signal
ing voltage of desired frequency and periodically
ing the positive half cycle of the interrupting fre
interrupting this voltage at a desired rate reside
quency; and with a negative grid bias, the sig
in its simplicity, its low initial cost, and the low
nalingyfrequency is interrupted during the nega
cost of maintenance Which results in part from
tive ' half-cycle of the interrupting frequency.
the lack of moving parts.
When the grid bias is zero, there is current in the
What is claimed is:
grid-cathode circuit during the positive half
1. A signaling -current generator comprising a
cycle of the interrupting frequency; and, with a
single thermionic tube, two tuned circuits in the
low enough ratio between the amplitudes of the
signaling and interrupting frequencies, the drop
inpotential in resistor I9 is effective to substan
anode-cathode circuit of said tube, one of said
50 tuned circuits resonant at a desired signaling fre
tially prevent variation in the grid potential due
quency, the other of said tuned circuits resonant
to the signaling frequency so that oscillation at
the signaling frequency ceases. With zero grid
bias, there is no grid current and no drop; in po
tential in -resistor I9, during the negative half
cycle of the interrupting frequency and the am
pliñcation of the tube is sufñcient to maintain
oscillation at the signaling frequency. If a
source of negative grid bias is provided in the con
trol grid-cathodecircuit, the instantaneous po
tential of the grid varies under control of the
feedback potentials; and in this case, there is no
grid current and no drop in potential in resistor
I_ 9 except during excessive peaks in the sum of the
at a desired lower frequency, feedback connec
signaling frequency, a network tuned to reso
nance at a desired lower frequency, said net
works connected in the anode-cathode circuit of
said tube, feedback connections from said net
instantaneous' feedback potentials of both fre
v works to the control grid of said tube, means
quencies. ' With sufficient regulation provided by
element 35, such excessive peaks will not occur or
will not 'be` suiñciently long in duration to sup
press oscillation at the signaling frequency dur
controlling the relative amplitude of the feed
back from said networks to effect a periodic in
terruption of the oscillations of said signaling
frequency at said lower frequency, output ter
lminals, and> means connecting'said terminals to
thenetwork tuned to the signaling frequency.
ing' positive half-cycles of the interrupting fre
quency; but, during the negative half-cycles, the
grid potential is driven to and beyond the oscil
lation cut-off point by the energy stored in the
circuit which is resonantv at the interrupting fre
quency. Whenlthis storedl energy is dissipated
tions frorn said tuned circuits to the control grid
of said tube, and means controlling the relative
amplitude of the feedback from said tuned cir
cuits to effect a periodic interruption of the oscil
lations of said signaling frequency at said lower
frequency.
2. In an oscillation generator, a single Vacuum
tube, a network tuned to resonance at a desired
3." In an oscillation generator comprising a
single vacuum tube, two tuned networks con
nectedin the anode-cathode circuit of said tube,
each-of said networks .comprisingan inductive
2,409,620
5
6
winding and a condenser, one of said networks
being resonant at a desired signaling frequency,‘
the other of said networks being resonant at a
desired interrupting frequency, feedback con
nections from said networks to the control grid
6. In an oscillation generator comprising a
single vacuum tube, two tuned networks con
nected in the anode-cathode circuit of said tube,
each of said networks comprising an inductive
winding and a condenser, one of said networks
of said tube, means controlling the relative am
.being resonant at a desired signaling frequency,
plitude of the feedback from each of said net
the condenser of said other network being vari
works to effect a periodic interruption of the
able so that the frequency at which said other
oscillations in said one network at said inter
network is resonant may be adjusted within de
rupting frequency, and an impedance element
sired limits, feedback connections from said net
having a negative impedance voltage coefficient
works to the grid of said tube, means controlling
shunting a part of the inductive winding of the
the amplitude of the feedback from each of said
network which is tuned to said signaling fre
networks to effect the periodic interruption of
quency, thereby to regulate the amplitude of the
the oscillations of signaling frequency at the
oscillations of the signaling frequency.
15 frequency to which said other network is reso
4. In an oscillation generator comprising a
nant, output terminals connected to said one
single vacuum tube, two tuned networks con
network, and an impedance element having a
negative impedance-voltage coefficient connected
nected -in the anode-cathode circuit of said tube,
each of said networks comprising an inductive
to the inductive winding of said one network to
winding and a condenser, one of said networks 20 regulate the voltage impressed across said ter
being resonant at a desired signaling frequency
minals.
`
and the other of said networks being resonant at
7. In an oscillation generator comprising a
a desired interrupting frequency, an adjustable
single vacuum tube, two tuned networks con
feedback connection from said one network to the
nected in the anode-cathode circuit of said tube,
control grid of said tube, an adjustable feedback 25 a ñrst one of said networks comprising one wind
connection from said other network to the con
ing of an induction coil and a condenser, said
trol grid of said tube, output terminals connected
first network being resonant at a desired low fre
to the inductive winding of said one network,
quency, the second one of said networks coin
and an impedance element having a negative im
prising windings of an induction coil and a con
pedance-voltage coeñicient connected to the in 30 denser, said second network being resonant at
ductive winding of said one network to constitute
a desired signaling frequency, means comprising
a voltage regulating load.
Y
‘
another winding of the first-mentioned induction
5. In an oscillation generator comprising a
coil `and a potentiometer connected across said
other winding for impressing an alternating po
single vacuum tube, two tuned networks con
nected in the anode-cathode circuit of said tube, 35 tential of said low frequency on the control grid
each of said networks comprising an inductive
of said tube, means comprising a potentiometer
and a condenser connecting said potentiometer
winding and a condenser, one-of said networks
being resonant at a desired signaling frequency,
in series with said second network for impressing
an alternating potential of said signaling fre
desired interrupting frequency, feedback connec 40 quency on said control grid, output terminals
tions frorn said networks to the grid of said tube,
connected to said second network, and means
a high resistance connected in the grid-cathode
including an impedance element having a neg
circuit, means controlling the amplitude of the
ative impedance voltage coefficient connected
feedback from each of said networks to eifect
across one of the inductive windings of said
the periodic interruption of the oscillations of
second network for regulating the amplitude of
said signaling frequency at said interrupting fre
the oscillations of said signaling frequency,
quency, output terminals connected to said one
whereby said oscillations are interrupted peri
the other of said networks being resonant at a
network, and an impedance element having a
negative impedance-voltage coefficient connected
odically at said low` frequency and the voltage
impressed across said terminalsv is maintained at
across a part of the inductive winding of said 50 a desired amplitude.
one network.
WALTER W. FRITSCHI.
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