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Oct.. 15, 1946°1
L. E. `MßcrsoN, JR
2,409,577
SYNCHRONIZED BLOCKING OSCILLATOR
Filed Dec. 3. 1943
BY
WV
ATTORNEY
Patented Oct. 15, 1946
2,409,577
UNITED sTATEs PATENT OFFICE
2,409,57 7
SYNCHRONIZED BLOCKING OSCILLATOR
Leslie E. Matson, Jr., Merchantville, N. J., assignor
to Radio Corporation of America, a corporation
of Delaware
Application December 3, 1943, Serial No. 512,681
5 Claims. (Cl. 250-36)
l
2
This invention relates to oscillation generators,
nization of the first of a series of oscillation trains
or pulses with a suitable external signal.
There are many uses for apparatus of the type
Referring to the drawing, I show therein a
discharge tube I which is preferably of the
pentode type having a cathode 2, an anode 3, a
control grid 4, a second grid 5, and a suppressor
grid 6. The cathode 2 is grounded and is Valso
connected to the grid E through a resistor 1.
The input circuit of the oscillator proper includes
a grid leak resistor 8 connecting grid 4 to ground.
to Which this invention relates.
Feedback means are coupled to this circuit and
and more particularly to an oscillator which
blocks itself automatically, and is provided with
means for control of the intervals during which
it intermittently oscillates, and also for synchro
One require
ment in some of the applications involved is that
there shall be made available apparatus for pro
ducing a succession of periodically recurrent os
include a transformer 9, the primary I6 of which
is in the output circuit of the oscillator, while»
the secondary'V II is coupled to the grid 4 across
cillation trains; that is, trains of equal duration
capacitor I2. Anode potential is supplied to the
and equally spaced apart in time. Another re
anode 3 across the transformer primary I0, be
quirement is that the ñrst train in such a group 15 ing delivered by a direct current source I3. This
shall be synchronized with the leading edge of
source also supplies screen grid potential to the
a square Wave impulse of relatively low fre
grid 5 across resistor I4. The usual by-pass con
quency. Blocking oscillators are, therefore, capa
denser I5 is provided, one terminal of which is
ble of improvement in accordance with the dis~
connected to the screen grid 5 while the other
closure of this application so that each train of 20 terminal is grounded. Any suitable utilization
oscillations shall consist of a uniform number
device may be coupled to the oscillator at the
of cycles (usually one cycle), and the initiation
terminals labelled “output,” Where one of these
of the first of a group of trains of oscillations is so
terminals is coupled to the anode 3 across capaci
controlled as to be precisely synchronized with
a particular phase of the applied rectangular
tor IE.
wave.
It is an object of my invention to provide a
blocking oscillator of vnovel type wherein the
periods of oscillation are controlled by an ex
ternal source of rectangular Waves.
The output may, however, be taken at
, any of several other points.
30
It is a further object to provide a blocking
oscillator wherein the leading edge of a square
wave and the trailing edge thereof shall serve to
initiate and to stop respectively the generation
of oscillations.
35
Still another object of my invention is to pro
vide a blocking oscillator having a pentode tube
in which the cathode, first grid, and anode are
included in the oscillatory circuit, the second
grid being arranged to function as a screen and 40
the third grid being used to initiate and to stop
the oscillations in dependence upon the keying
of an externally derived control potential.
Another object of my invention is similar to
that set forth in the preceding paragraph but 45
with the added feature that an auxiliary tube is
provided for varying the control potential ap
plied to the third grid of the oscillator tube.
The forego-ing and other objects and advan
tages of my invention will be made clear from
the description to follow. This description is ac
companied by a drawing, the sole figure of which
shows a preferred circuit diagram of apparatus
units which are combined for carrying out the
invention.
55
If the suppressor grid 5 is maintained at cath
ode or ground potential, tube I generates inter~
mittently blocked oscillations by virtue of a feed
back circuit through transformer S, the oscillatory
electrodes being the cathode, the anode, and the
control grid, as is conventional. If, however, a
negative potential is applied to the suppressor
grid with respect to the cathode 2, then the
oscillations are stopped. In order to supply this
negative potential, an auxiliary control tube I'I
is provided. This tube may, if desired, be of the
triode type having a cathode I8,- an anode I9,
and a control grid 20. A cathode resistor 2l is
here shown, this element being preferably used
to avoid tube saturation.
An independent direct current source applies
a negative potential to the cathode I8 through
resistor 2|, the positive terminal of this source
being grounded. The input circuit for tube il
includes a grid leak resistor 23 connected between
the grid 2l] and the negative terminal of the
source 22. Grid 20 is also arranged to be fed
with control potentials across capacitor 24.
These control potentials develop a suitable volt
age drop across the resistor 23. Input terminals
25, one of which is grounded, may be used for
applying suitable control potentials. These po
tentials are preferably of the rectangular or
square wave type in order that the leading and
2,409,577
3
4
trailing edges of the wave may be sharply de
fined.
In the operation of my invention, it will be
tions, and a keying circuit for at times blocking
said oscillations, said keying circuit comprising a
second discharge tube having at least a cathode,
seen that the square wave input constitutes a
an anode and a control grid, the anode whereof
gate voltage which controls the space path im
is directly connected to a grid of the oscillator
tube adjacent its anode, an input circuit con
pedance in the tube I'I. When this tube is blocked
by a negative potential on the grid 20, then the
anode I9 stands at ground potential since there
is no voltage drop across the resistor 'I under
nected between the cathode and control grid of
said second discharge tube, and an output circuit
for the second discharge tube including a direct
When, however, tube I1 is 10 current source the positive terminal of which is
these conditions.
rendered conductive, it draws current by virtue
of the negative potential applied to its cathode I8
maintained at the cathode potential of the iirst
said tube, a ñxed resistor being interposed be
tween said positive terminal and the anode of
from the source 22. The current traversing re
the second discharge tube.
sistor 'i developsl a voltage drop which thereupon
2. In combination two electron discharge tubes,
renders the suppressor grid 6 strongly negative. 15
each having a cathode, an anode, and one or
Hence, the tube I is biased to cut-oil and the
more grids, input circuits and output circuits
oscillations instantly cease.
individual to each of said tubes, the input and
In this description of operation it should be
output circuit of one of said tubes being so inter
emphasized that in usual practice the oscilla
tory state exists in ,a blocking oscillator during 20 coupled as to cause that tube to generate pe
riodic and discrete oscillatory trains, two sources
periodic intervals which are very brief compared
of direct current, each individually constituting
with the intervals during which the oscillator
a means for supplying power to a respective one
is blocked. The ratio between oscillating times
of said tubes, direct ground connections for the
and blocking times depends, of course, upon the
negative terminal of the source which supplies
circuit constants. A “train” of oscillations, as
power to the oscillator tube and for the posi
herein referred to, consists of the single impulse
tive terminal of the source which supplies power
or the plurality of impulses produced prior to
to the other tube, a load impedance connected
each blocking period. Commonly, the blocking
between ground and the anode of said other
state is reached so suddenly that only a single
tube, a direct connection between that anode and
cycle exists in each train. Under some circum
a grid in the oscillator tube other than its oscil
stances, however, each train may comprise a plu
lator grid, and means for so controlling the
rality of cycles. The function of the externally
space path impedance in said other tube that,
derived rectangular wave is to periodically ter
when conductive, it interrupts the periodicity of
minate the blocking periods. Thus it is possible
production of said oscillatory trains.
to control the starting time for the first of a
3. Apparatus for alternately initiating and in
group of oscillatory trains in accordance with
terrupting trains of oscillations generated in a
the steep wave front of a rectangular wave and
discharge tube which possesses oscillatory and
to permit the oscillator to deliver a succession
suppressor electrodes, said suppressor electrode
of “trains” comprised in that group during the
persistence of a half cycle of said rectangular 40 being iixedly connected through an ohmic resist
ance to the cathode of said tube, comprising a
wave.
second discharge tube in which the space path
At the instant when a group of oscillation
impedance is varied by a rectangular wave input,
trains is again to be initiated in tube I, the trail
this second tube having its anode resistively con
ing edge of the rectangular wave input to tube
I'I blocks this tube so as to restore the ground
1 nected to the cathode of the ñrst said tube, means
potential to its anode IQ. Thereupon the sup
pressor grid S in tube I is brought back to ground
potential and the generation of oscillations is re
pressor electrode at all times with the anode
sumed.
It will be noted that the degree of accuracy
for equalizing the bias potential of said sup
potential in said second discharge tube, and
means for shifting said anode potential from
that of the cathode in the first said tube to a
with which the oscillatory trains are synchro
more negative potential whenever the oscillatory
nized with respect to an external source of rec
trains are to be blocked.
4. A control circuit comprising a vacuum tube
to be controlled, said vacuum tube having an
anode, a cathode, a control grid and at least
one other grid, an input circuit connected be
tangular waves depends upon the abruptness of
transition between conductive and non-conduc
tive states in the tube I'I. Hence by a carefully
selected choice of circuit components, the control
and synchronizing of oscillatory trains can be
made as precise as is desired.
tween the control grid and cathode, said cathode
being connected to ground, an output circuit
connected between said anode and cathode, a re
My invention is capable of modiñcation in
numerous ways without departing from the spirit 60 sistor connected between said "other” grid and
the grounded cathode, a controlling vacuum tube
and scope thereof. For example, it is not at
having a plate, a control grid and a cathode, a
all essential that the control potentials applied
cathode return circuit including a source of oper
to the tube Il' shall be periodic. In certain ap
ating potential connected between the cathode
plications, it is required that they shall be
aperiodic, but that they, nevertheless, shall be f“ of the controllingtube and ground, the plate of
said controlling tube being connected to said
enabled to initiate and to block the oscillatory
other grid in the first mentioned tube and the
trains generated by tube I regardless of their
plate circuit including said resistor, and means
duration and of the duration of the blocking
periods.
for rendering said controlling tube alternately
I claim:
1. In a device of the class described, an oscilla
tion generator comprising a discharge tube hav
ing a cathode, an anode, and at least two grids,
conductive and non-conductive thereby to neg
ativeiy bias said “other” grid of the tube to be
controlled during conductive periods of the con
resonant circuit means connected to the Vcath
ode, anode, and ñrst grid for producing oscilla
trolling tube.
5. In combination, a blocking oscillator com
75 prising a multi-grid discharge tube and means
2,409,577
coupling its output to one of its grids for apply
ing feedback potentials thereto, a keying control
device directly connected between the cathode
of said tube and a grid adjacent its anode, said
connections for the cathode of the oscillator tube,
the negative terminal of the source in the oscil
lator output circuit, and the positive terminal of
the source in the output circuit of the tube in
device comprising a fixed impedance in the out Ul said keying control device, the negative termi
put circuit of a discharge tube the conductive and
nal of the last mentioned source and the cathode
non-conductive states of which are controlled by
of the tube in said keying device being intercon
an external source of rectangular Waves, inde
nected through a cathode resistor.
pendent sources of direct current in the respec
tive output circuits of said tubes, and ground l0
LESLIE E. MATSON, JR.
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