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; (MW Ila/WW“
Dec‘ 24, 1946.
Filed Feb. 10, 1945
‘M2 21,;
' Kziédeu?d
fwéshe. Wilma 7" W
be _m
.4 Guihc‘ord LHoHingsvvor-th,
Richard C.Jensen,
Their‘ Attorney.
Patented Dec. 24, 1946
A 2,413,182 "
Guilford L. Hollingsworth, Schenectady, and
Richard C. Jensen, Scotia, N. Y., assignors to
General Electric Company, a corporation of
New York
Application February 10, 1943, Serial No. 475,352
5 Claims.
(Cl. 250-36)
This invention relates to communication sys
tems and more particularly to pulse generators
for such systems.
former coupling between the ampli?er stages
permits all discharge devices to be operated with
grounded cathodes, thus making special, low ca
pacity ?lament transformers unnecessary and al
It is an object of our invention to provide a
pulse generator of improved stability and reli
lowing all ?laments to be operated from a com
mon source.
It is another object of our invention to provide
new and improved means for accurately and sim
ply varying the width of the pulses produced in a
In order accurately to control the width of the
pulses impressed on. the ampli?ers and also vto
terminate the pulses or to decrease the time dura
pulse generator,
tion of the pulses to a shorter period 'o_f__tir_ne than
is possible in the output of the multivibrator,
Still another object of our invention is to pro
vide a new and improved pulse generating means
‘there is provided a ‘feedback circuit betweenil?
in which the pulse width is substantially inde
output of the ampli?er stage l4 and the control
electrode circuit of the ?rst ampli?cation stage
pendent of variations in circuit voltages, tem
perature variations, and changes in the charac
teristics of the discharge devices with age.
15 l2.
The feedback circuit comprises a suitable
~delay means H, which may be adjustable if de
Multivibrators are frequently used in pulse gen
sired, for causing a negative potential to be ap
erating devices. Because of stray capacity ef
plied to the control electrodes of the electron dis
fects, etc., the minimum uls width for a multi
charge device 66 of the ampli?er l2 at a predeter
vibrator is of the order of one microsecond. It is 20 mined time after the initiation of the pulse.
also an object of our invention to provide a new
When the feedback voltage appears at the ?rst
and improved pulse generator of the type employ
driver or ampli?er, it cuts off the pulse thus
ing mpable of accurately
making the pulse width equal to the delay time of
producing pulses of width less than one micro
the delay means.
Describing our invention in greater detail, the
' The features of our invention which we believe
multivibrator l0 illustrated herein comprises a
to be novel are set forth with particularity in ‘the
appended claims. Our invention itself, both as to
its organization and manner of operation, to
double triode discharge device 20 having anodes
2|, 22, control electrodes 23, 24 and cathodes 25,
26. The cathodes are connected together and to
gether with further objects andadvantages there 30 ground. In order to provide anode potential for
of, may best be understood by reference to the
the multivibrator there is provided a recti?er 28
following description taken in connection with
which may comprise a transformer 29 having a
the accompanying drawing in which Fig. 1 is a
primary winding 30 connected to ‘a suitable source
circuit diagram of a radio communication system
of alternating current and secondary windings 3|,
embodying the principles of our invention, Figs.
32, 33 and 34. The winding 3| may be utilized
2 and 3 illustrate pulse shapes at various portions
for supplying power to the heaters of the elec- _
of the circuit of Fig. 1, and Fig. 4-. illustrates a
tron discharge devices used in the circuit. The
modi?cation applicable to the circuit of Fig. 1.
high voltage winding 32 is connected to the an
In the drawing there is illustrated a pulse gen
odes 35 of the full wave rectifying device 36. The
erator including a multivibrator [0 which is of 40 secondary winding 33 provides the ?lament cur
the start-stop type. Since the output of the mul
rent for the ?lament 31 of the rectifying dis
tivibrator is negative, it is followed by a clipper
charge device. The center tap of the winding 32
inverter stage II to produce substantially square
constitutes the negative terminal for the recti?er,
pulses of positive polarity to drive the ?rst stage
which is grounded, and one side of the ?lament
of ampli?cation, indicated by the numeral l2. 45 31 constitutes the positive terminal of the rec- The ampli?er I2 is transformer coupled to a sec
ti?er. The output of the recti?er is suitably ?l—
ond ampli?er stage M by means of a transformer
tered by ?ltering means comprising an inductance
[3. In order to obtain economy of anode power,
both stages of ampli?cation are operated with
cutoff bias applied to the control electrodes of the
discharge devices associated therewith so that the
ampli?er l2 draws anode current only during the
period of the pulses. The output of'the second
ampli?er stage is applied to an oscillator l5 which
may be of the magnetron type. The use of trans 55
38 and a plurality of condensers 39.
The anode 2| of the multivibrator is connected
to a point of positive potential through the re
sistances 40 and 52, and the anode 22 is con
nected to a point of positive potential through
an inductance 98 and series connected resistors
4| and 52.
The control electrode 23 of the left-hand por
tion of the discharge device 20 is connected to
ground through the switch 42 and one of the re
sistors 43, the purpose of which is described later.
The control electrode 24 of the right-hand por
tlon of the discharge device 2|] is connected to a
source of negative potential, indicated by the nu
meral 45, through a suitable resistor 44.
The source of potential 45 is illustrated as com
cause the left-hand portion of the device to be
come operative. Variations between different
tubes, change of characteristics of various dis
charge devices with age, temperature and voltage
variations, etc., cause variations in the required
triggering potential, thus producing inaccuracy
in the time of ?ring. However, if the input por
tion is normally conducting, the appearance of a
small negative potential on the control electrode
prising a half wave recti?er device 450, the ?la
ment of which is connected across the secondary 10 causes
It is apparent from the above description that
winding 34 of the transformer 29 and one of the
a negative pulse is produced and impressed on
?laments of which is connected to the anode 35
the load resistance 4|. Means is provided for
of the rectifying device 36 so that the right-hand
varying the width of the output pulses. If both
portion of the winding 32 is utilized as the alter
sides of the multivibrator circuit have substan
nating current source for the recti?er 45a. In 15 tially the same resistance and capacity, the on
series with that portion of the winding 32 and
and oil times of the sides of the discharge device
the rectifying device 45a is a voltage divider com
20 will be relatively equal under free running
prising series connected resistances 46, 41 and 48.
conditions. Means is provided for varying the
In order to ?lter the direct current output of the
time constant of the left-hand side of the device
recti?er there are provided suitable condensers
by connecting the control electrode 23 to ground
49, 50 and 5| connected in parallel. One side of
through one of a plurality of resistances 43, each
each condenser ds grounded, the other sides are
of the resistances having a different value. The
connected by resistances 46 and 41 and resistor
provision of a selector switch 42 enables choice
49 is connected in shunt with condenser 5|. In
to be made of the grid leak resistance connected
spection of the circuit of the recti?er indicates 25 to the control electrode. By varying the time
that the left-hand end of resistance 46 is at the
constants of the left-hand side of the multivi
most negative potential and the lower end of 48
brator, the opposite, variation is attained on the
is at the most positive potential. Therefore, a
right-hand side. Therefore, the width of the
negative potential is applied to the electrode 24.
negative pulses appearing on resistance 4| is de
In order to cause operation of the device In
pendent upon the position of the switch 42.
in regular multivibrator fashion there is provided
In order to cause operation of the multivibrator,
a condenser 53 connected between the anode 22
there is provided a suitablesource of signal volt
and the control electrode 23 and another con
age, 55, as, for example, a source of square waves.
denser 54 connected between the control electrode
The signal voltage may be impressed on the elec
24 and the anode 2|.
trode 23 through a potential divider indicated by
With the circuit shown, the right-hand side of
the numeral 56 and a coupling capacity or con
the discharge device 20 is normally non-conduct
denser 51.
ing and the left-hand portion conducting because
The negative pulses produced by a multivi
of the negative bias applied to control electrode
brator of the type illustrated and described herein
24. If for any reason there is a slight decrease
normally have approximately the shape shown
in the potential on the control electrode 23, the
in Fig. 2a although proportions are greatly ex
?ow of current through the left-hand portion of
aggerated for clearness of illustration. The in
the discharge device 20 is decreased. Therefore,
ductance 99 is provided to cause a more nearly
the anode potential, which was relatively low be
rectangularly shaped pulse to be formed. The
cause of the discharge through the device, in
inductance should be of such a value that it co
creases. Due to the coupling condenser 54, the
operates with the stray capacity of the circuit
potential of the control electrode 24 becomes less
to give the equivalent of a parallel resonant cir
- negative.
cuit at relatively high frequencies. As a result,
right-hand portion of the discharge device 20
the output circuit will pass more high frequency
begins to conduct, the anode potential suddenly
components and give a more nearly rectangular
decreases, and the coupling capacitor 53 causes
pulse as indicated at b in Fig. 2.
the left-hand control electrode 23 to go negative
In order to invert the pulses and render the
beyond cuto?. At the same time the conduction
pulses still more rectangular, the negative pulses
through the right-hand portion reaches a maxi
mum. This condition remains substantially con 55 are impressed on the inverting device || through
stant for a time determined by the resistance and
capacity in the multivibrator circuit. After ex
piration of that time the condensers 53' and 54
no longer maintain constant the potentials of the
associated control electrodes because of current
?ow through the resistances connected thereto
and the entire action tends to take place in the
a coupling condenser 58. The inverter may com
prise an electron discharge device 59 of the pen
tode type, the negative pulses being applied to
the control electrode 60 which is also connected
to ground through a suitable grid leak 6|. The
cathode and suppressor electrode are grounded.
The anode 62 is connected to a suitable positive
potential through an inductance 63 and a suit
reverse direction. Inasmuch as there is a nega
able resistor 63a. The negative pulses appearing
tive bias applied to the control electrode 24, op
on the control electrodes 60 cause a decrease in
eration halts after one pulse is produced unless
the amount of current ?owing through the elec
a suf?ciently negative potential again appears on
tron discharge device and therefore cause an in
the control electrode 23.
crease of the anode potential. The discharge de
The arrangement described above is advanta
vice 59 is preferably arranged so that the appear
geous because relatively good accuracy of opera
tion is achieved. It the left-hand portion is 70 ance of pulses on the control electrode drives the
device beyond cut-o? and thereby produces a sub
normally non-conductive a positive triggering
stantially flat topped pulse. As a result the ex
potential on electrode 23 is required to initiate
treme tip of the pulse is clipped as indicated by
operation of the multivibrator and conduction in
the horizontal dash line in Fig. 3a. In the absence
the right-hand portion takes place until the po
tential of control electrode 23 rises sufficiently to 75 of the inductance 63 the resultant pulse is ap
proximately wedge-shaped, as indicated by the 4
portion of Fig. 3a below the dashed line, but, as
was the case with the inductance 99, presence of r
16 in the second ampli?er. ‘The negative pulses
appearing in the output of the discharge device
larly shaped pulse to be produced as shown in
Fig. 3b. The positive pulses are coupled to the
16 are impressed on a utilization circuit such as
an oscillator. For illustrative purposes, the
utilization circuit is shown to include a magnetron
l5 upon the cathode circuit of which pulses are
control electrodes 64 of the ampli?er or driver 14
which may comprise a device 66 of a double tetrode
impressed and which is connected to an antenna
86 to transmit therefrom rapidly repeated, short
type by means of a coupling capacitor 61 and re
sistors 68. The control electrodes 64 are con
duration, pulses of intense micro-wave radiation.
nected through the resistances 68 and the resist
approximately two to one million pulses per sec
ond and therefore the pulses vary in width from
one-half a second to one microsecond. The ex
planation of the narrow limit is possibly the pres
15 ence of stray capacities. In order to enable the
production of narrower pulses than possible with
ordinary multivibrator operation and at the same
time to insure accurate pulse width, there is pro
the inductance 63 causes a more nearly rectangu
ance 68a to a suitable negative tap on the voltage
divider of the source of potential 45. With this
arrangement the discharge device draws current
only during the time a su?iciently positive pulse
is applied.
Inasmuch as negative pulses appear in the out
Multivibrators are capable of operation from
put of the ampli?er l2, means is provided for in
verting the pulses before application to the ?nal
vided apparatus utilizing the pulses from the out
output stage l4. This means comprises, in the 20 put of the discharge device 18 for terminating
the pulses applied to the ?rst ampli?er stage 12
villustrative ,form of our invention, atransformer
I3 having a primary winding 69 and a secondary
at predetermined times.
winding 14. One end of the primary 69 is con
The ancde-to-cathode voltage of the-discharge
device 16 is applied through a condenser 89,to
ducted through the anode resistances 69a to the
anodes of the electron discharge device 66 and 25 a voltage divider comprising series connected re
sistances 90, BI and 92. A predetermined portion
the other end of the primary winding is connected
of the voltage across the voltage divider is fed
to a suitable source 10 of positive potential.
back to the control electrodes 64 through the
The last mentioned source may comprise a half
wave recti?er ‘H and a transformer having a pri
resistor 93, a switch 94, and a suitable delay
mary connected to a suitable source of alternat
30 means I1, such as an arti?cial transmission line,
and a coupling condenser 95.
ing current and a. high voltage winding connected
The delay means I‘! may comprise a plurality
between ground and the anode. The ?lament
of parallel-connected condensers, one side of each
winding is connected across the ?lament of the
being grounded and the other sides being con
recti?er. With this arrangement the center tap
of the ?lament transformer constitutes the posi 35 nected by inductances 91. The resistors 93 and
98 are connected across the line at each end
tive terminal of the source. In order to ?lter the
output of the recti?er there is provided a suitable
thereof in order properly to terminate the trans
mission line and to prevent re?ections. Inas
condenser 13. The secondary transformer wind
much as negative pulses are fed back, the control
ing 14 is connected between the control electrode
15 of the discharge device 16 and the negative 40 electrodes 64 have applied thereto a negative
potential which cuts off or neutralizes the pulses
terminal of the source of potential 45.
at times dependent upon the constants of the
The lower end of the winding 14 is connected
delay circuit, thus making the pulse width equal
to ground for radio frequency currents through
to the delay time of the line.
the ?lter condenser 49. With these connections
Means is provided for varying the time delay,
the control electrode 15 is biased beyond cutoff 45
the illustrative means comprising the switch 94
and therefore current flows only during the ap
having a movable arm and a plurality of switch
points, the points being connected to different
In order to provide potential for the screen
combinations of capacity and inductance in the
electrode of the discharge device 16 there is pro
vided a voltage divider including resistances 80 50 time delay circuit. It is undesirable, in the ar
rangement shown, to cut off more than one-half
and Bi connected across the output of the rec
of each of the pulses because if a feedback pulse
ti?er 10, that is, from ground to the midtap of
plication of a sufficiently positive pulse.
the secondary winding of the ?lament trans
former 12a. Radio frequency currents are by
is initiated before the ?rst half of the pulse has
passed through the amplifying device l2, the
passed to ground by means of a suitable con
55 pulse will be terminated so early in a pulse cycle
denser 82 connected between the screen electrode
and ground. Anode potential for the discharge
that the delayed pulse is terminated before the
inverted pulse from the clipper and inverter II
has disappeared from the control electrodes 64
device 16 is obtained from a suitable source,iindi
and therefore two pulses instead of one appear
cated by the plus sign, through an inductance 83
and a resistor 84. If the oscillator or source of 60 in each pulse period. In such a case the two
pulses are usually of different widths. Therefore,
high frequency oscillations is of the magnetron
type, as illustrated, a relatively high source of
the switch arms of switches 42 and 94 are prefer
potential is provided as, for example, 15 kilo
volts. The coil or winding 83 is provided for the
ably connected together for simultaneous change
damp out the voltages developed by the induct
creased in like proportion. If desired, time delay
so that as the width of the multivibrator pulses
same purpose as the previously described anode 65 are increased under the control of the switch 42
the amount of delay pulse fed back can be in
inductances. The resistance 84 is necessary to
circuits may be cascaded so that the shortened
pulses can be impressed on a second delay circuit,
the tails of the pulses. Therefore, substantially
square pulses are applied to the oscillator.
70 and so on. This modi?cation is particularly
practicable if low gain ampli?er stages are used.
Under the foregoing circuit conditions, the neg
ative pulses appearing in the output of the am
After the ?nal narrowing operation, a high gain
ance 83 and minimizes or prevents oscillations on
pli?er stage 12 are inverted in the secondary of
ampli?er may be used bene?cially.
the transformer l3 and appear as positive pulses
In order to insure a steep rise on the leading
on the control electrode 15 of the discharge device 75 edges or the pulses applied to the ampli?er l2,
the circuit of Fig. 1 may be modi?ed, as shown
in Fig. 4, by providing a series connected con
denser 93 and resistance Hill between the control
electrode 15 of discharge device ‘I6 and a point
between the resistances BB and the condenser 61.
With this arrangement, the voltage from the
secondary of transformer I3 is fed back to the
ampli?er l2. The condenser 99 should be of
such capacity that it becomes fully charged at
or before the pulse reaches its peak amplitude
so that feed back occurs only during the rise
said output circuit for disabling said amplifying
means and terminating said output pulse prior
to termination of the impressed pulse.
3. In a radio communication system, means for
producing a succession of discrete pulses, means
for amplifying said pulses, means for impressing
said pulses on said amplifying means, said am
plifying means having an output circuit in which
the ampli?ed pulses appear, regenerative means
for feeding back to said impressing means dur
ing initiation of each of said pulses a voltage
from said output circuit in such phase that there
of voltage. The value of the resistance I00 should
is produced a steep rise on the leading edge of
be such as to enable the desired amplitude of
each of said pulses, and delayed degenerative
voltage to be obtained. Thus, if the voltage fed
back is too great, the amount of resistance should 15 feedback means responsive to initiation of each
pulse in said output circuit for disabling said
be decreased, and vice versa.
amplifying means and terminating said output
While we have shown and described a particular
pulse prior to termination of the impressed pulse.
embodiment of our invention. it will be obvious
4. In a radio communication system, means for
'to those skilled in the art that changes and
modi?cations may be made without departing 20 producing a succession of discrete pulses, means
for amplifying said pulses including an electron
from our invention in its broader aspects, and
discharge device having a control electrode, an
we, theref0re,;-aim in the appended claims to
anode, and a cathode, an input circuit between
cover all such 'changes and modi?cations. as fall
said control electrode and said cathode, and an
within the true spirit and scope of our invention.
What we claim as new and desire to secure by 25 output circuit between said anode and said cath
ode, means for impressing said pulses on said
input circuit, a transformer coupled to said out
put circuit, and means including a capacitor for
for producing a succession of discrete pulses of
deriving from the secondary winding of said
predetermined time duration, means for amplify
ing said pulses, means for impressing said pulses 30 transformer and supplying to said input circuit
during initiation of each of said pulses a voltage
on said amplifying means, said amplifying means
in such phase that there is produced a steep rise
having an output circuit in which the ampli?ed
on the leading edge of each of said pulses.
pulses appear, means utilizing each of said ampli
5. An electric pulse generating system com
?ed pulses for disabling said amplifying means
at predetermined times less than the full time 35 prising means for producing a series of discrete
pulses of predetermined time duration, amplify
duration of said pulses, and means utilizing the
ing means for said pulses including input and
voltage appearing in said output circuit at the
output circuits, regenerative means coupling said
initiation of each of said pulses for‘causing the
input and output circuits for increasing the steep
pulses impressed on said ampli?er to have a steep
rise on the leading edges thereof.
40 ness of the leading edge of each of said ampli
fied pulses, a transmission line section ener
2. In a radio communication system, means for
gized by said ampli?ed pulses independently to
producing a succession of discrete pulse-s, means
measure a predetermined time interval after in
for amplifying said pulses, means for impressing
itiation of each of said pulses, said time interval
said pulses on said amplifying means, said am
plifying means having an output circuit in which 45 being less than said predetermined time dura
tion, and means connecting said time delay net
the ampli?ed pulses appear, means utilizing the
work periodically to disable said amplifying
voltage appearing in said output circuit at the
means thereby to terminate each of said ampli~
initiation of each of said pulses for causing the
pulses impressed on said ampli?er to have a steep
?ed pulses at the end of said time interval.
rise on the leading edges thereof, and delay 50
means responsive to initiation of each pulse in
Letters Patent of the United States is:
1. In a radio communication system, means
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