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oet» 8, 1946.
`
H. M. s_TEARNs
y 2,408,821
AUTOMATIC VOLUME CONTROL
original Filed July so, 1942
4..
'
TEÉî/VS
ATTORNEY
2,408,821
Patented Oct. 8, 1946
UNITED STATES PATENT OFFICE
2,408,821
AUTOMATIC VOLUME CONTROL
Horace Myrl Stearns, Merrick, N. Y., assignor to
Sperry Gryoscope Company, Inc., Brooklyn,
N. Y., a corporation of New Yorky
Original application July 30, 1942, Serial No.
452,818. Divided and this application Novem
ber 6, 1943, Serial No. 509,225
16 Claims. (Cl. Z50-20)
1
This invention relates to automatic volume
control for radio receivers. Although the inven
tion is generally useful in all types of radio and
other signal receivers, it is described herein as
applied to a pulse receiver for a radio detection
system such as that shown in copending applica
tion Serial No. 452,818, filed July 30, 1942, in the
names of Eric J. Isbister, Horace Myrl Stearns,
and Walter N. Dean, of which the present appli
2
stages to produce an overall change in the ampli
ñcation of the receiver that is adequate to main
tain the output level substantially constant.
Since the potential applied to several screen
grids is to be controlled, the current supplied by
the source must be comparatively large. The
voltage applied to the screen grids of these tubes
may be readily adjusted by changing the resist
ance connected in series with the screen grids.
cation is a division.
According to the present invention in its preferred
An object of the invention is to provide an
automatic volume control circuit for controlling
the potential applied to the screen grids of ampli
fying tubes in a receiver to adjust the amplifica
tion of the receiver and thus to stabilize its
for the screen grids of the amplifying tubes in
several stages of the intermediate frequency am
pliñer. The resistance of this power tube is ad
output.
A further object of the invention is to provide
an automatic volume control circuit for control
ling a high potential, high current source supply
form, a variable resistance in the form of a power
tube is placed in series with the voltage supply
justed according to the average output level of
the receiver. To effect this adjustment, the power
tube is arranged in series with a high gain con
trol tube and a suitable impedance.
A voltage corresponding to the average output
level ofthe receiver is applied to the control grid
of the high gain control tube. This varies the
receiver’s output.
current drawn by the control tube through the
A still further object of the invention is to
power tube and impedance according to the out
provide an automatic volume control :circuit which
uses the average output level of a receiver to con 25 pu+u of the receiver, although variations in the
ing energy to the screen grids of amplifying tubes ~
in a receiver according to the average level of the
current through the power tube are comparatively
small. The voltage drop across the impedance
connected between the two tubes is used to con
trol the bias applied to the grid of the power
Other objects and advantages of the invention 30 tube. Since this drop varies according to the cur
rent drawn by the control tube, it corresponds to
will become apparent from the following specili
the output level of the receiver; the resistance of
cation, taken in connection with the accompany
the power tube is therefore also changed as the
ing drawing which shows a schematic diagram
output level of the receiver varies.
of a radio receiver employing an automatic vol
As the resistance of the power tube varies, the
ume control circuit embodying the invention in
drop across it due mainly to the current drawn
its preferred form.
by the screen grids of the amplifying stages also
It has previously been proposed to control the
varies according Vto the output level of the re
screen grid of an amplifying tube according to
trol a source of high potential applied to the
screen grids of amplifying tubes in a receiver in
a manner to maintain the output of the receiver
at a substantially constant level.
ceiver. The circuits are so arranged that an in
the output of a radio receiver in a manner to
maintain the output at a more or less constant 40 crease in the output intensity of the receiver in
creases the resistance of the power tube, thereby
level. However, difficulties have been encoun
tered, since the screen grid of an amplifying tube
demands a substantial amount of current at a
relatively high potential.
According to the present invention in its pre
ferred form, the screen grids of amplifying tubes
in several stages of the intermediate frequency
ampliñer of a radio receiver are supplied with a
voltage of a suitable potential that may be ad
justed according to the average output level of
the receiver in a manner to stabilize the output
level. An automatic volume control circuit em
bodying the invention permits a small change in
the output level to be applied to several screen
reducing the voltage applied to the screen grids
of the amplifying tubes and thus reducing the
overall ampliñcation of the receiver to maintain
its output level substantially constant.
Referring to the drawing, which shows a pulse
receiver for a radio detection system, pulses of
electromagnetic energy are collected by an an
tenne, I I. As is `well known in such detection sys
tems, an _object or tar-get is irradiated by short,
sharp pulses of electromagnetic energy and the
reflected pulses are _used to detect the presence
and position of the object.
’
APulses of electromagnetic energy collected by
grids in the intermediate .frequency amplifier 55 the antenna I I aresupplied to a conventional fre
3
4
quency converter I2, which may be a high fre
quency superheterodyne mixer including a suit
or slightly longer. The generated pulses are fed
by Way of a suitable coupling condenser 44 and
able local oscillator to produce the usual inter
mediate frequency wave. The intermediate fre
coupling resistor 45 to the control grid of blocking
ampliñer tube 46 whose cathode 4l' is connected
quency signal, modulated in this case by the re
ceived pulses, is supplied through a-coupling con
denser IS across a grid resistor I4 to control grid
It of an amplifying tube I8 shown as a pentode
connected in a conventional ampliñer circuit des
ignated by the numeral I9. This circuit forms ll)
to _a source of fairly high negative voltage indi
cated schematically as 48, and Whose anode 49 is
connected to ground through output resistor 5I.
The screen grid of tube 46 is connected directly
the first stage of an intermediate frequency am
plifier in the receiver. Plate 2I of the tubeV I8 is
connected through load resistor 22 to a' suitable
source 23 of positive potential, and cathode 24
is connected through a bias resistor 25 to ground.
Screen grid 26 of tube I 8 is connected by a lead
23 to a separate source of potential which is con
trolled by the automatic volume control circuit
embodying the present invention.
The output voltage of the ñrst stage I9 is cou- ~
to ground.
In this manner tube 46 is rendered
normally conductive, and the generated pulses
from the pulse generator 38 are adjusted to be
of such magnitude and polarity as to interrupt
the conduction of tube 46 for the duration of
these pulses.
Theungrounded terminal of resistor '5I is also
connected directly to anode 52 of a further block
ing ampliñer tube 53 of the pulse gate 36, whose
control grid 56 is energized by the receiver out
put Wave derived from the Wide-band amplifier
pled as by a condenser 3I to succeeding addi
34 and connected to the control grid through a
coupling condenser 58 and grid resistor 59.
tional intermediate frequency ampliiier stages 32,
Cathode e I' of the tube 53 is connected to a source
which are of similar design and have their screen
grids controlled in like manner from the auto
matic volume control circuit. The output of the
same as source 48. Tube 53 is also rendered nor
of fairly high negative voltage, which may be the
mally conductive, its> conductivity being decreased
intermediate frequency amplifier 32 is supplied to
in response to the pulses existing in the received
Wave input that is applied thereto.
Resistor 5I is included in the input circuit of
an amplifier tube 63 whose anode 64 is connected
.ventional wide band ampliñer 34 designed to 30 directly to a source 65 of high positive potential
maintain the Wave shape of received pulses.
and whose cathode 66 is connected to a source 61
The received pulses are also accompanied by
of low negative biasing potential through an out
interspersed stray noise Waves and other unde
put resistor 68 shunted by a condenser 69, Bias
sired pulses, due to multiple reflections or further
source 6'! may also be bypassed for alternating
reflecting objects, which might impair the de
current by means of a by-pass condenser 'II.
sired indications, In order to reduce the effect
In operation, in the absence of pulses applied to
of such interspersed noise and stray pulses the
tube :i6 and tube 53, the normal quiescent cur
received Wave from the wide band amplifier 34
rent through resistor '5I from tubes 46 and 53 will
is transmitted through a pulse gate 36 which is
produce a negative voltage thereacross suiiicient
a conventional second detector 33 where received
pulses are detected to obtain the modulation en
velope of the received Wave, which is fed to a con
adapted, as will be described, to permit only the 40 to overcome the bias of source 61 and to com
passage of the desired received pulses while effec
pletely cut-off tube 63. Accordingly, zero out
tively blocking or wiping out such extraneous
put voltage will appear at the output of tube
noise and stray pulses. Pulse gate 36 is placed
63, which is.supplied by lead l2 to the unground
under the control of a pulse generator 38 which
ed one or" a pair of terminals 13.
is adapted to produce a sequence of pulses having
When a pulse from pulse generator 38 is im
the same frequency or repetition rate as, and a
pressed on blocking tube 46 it momentarily de
duration substantially the same as or slightly
longer than, the received pulses. The time phase
of the generated pulses is made adjustable with
respect to the phase of the received pulses under
_the control of a suitable manual control adapted
to be actuated by the operator. Pulse gate 36, as
will be described, comprises a normally blocked
circuit which becomes unblocked only under the
iniiuence of the generated pulses. By suitably
adjusting the phase of the generated pulses to
,coincide with that of desired received pulses, the
desired received pulses may be transmitted to
suitable indicating and control circuits While
eliminating all undesired interspersed pulses and 60
creases the anode current of the tube 46 and ac
cordingly decreases the voltage drop across re
sistor 5I, However, the circuit values are so se
lected that tube 63 is nevertheless still blocked
in the absence of a corresponding simultaneous
pulse from the received Wave impressed on block
ing tube 53. When a pulse from pulse generator
33 is impressed on tube 46 simultaneously with a
received pulse impressed on tube 53, the resultant
decrease in current through resistor 5I is then
suliicient to reduce the bias on tube 63 to a point
where cathode current can iioW.
Accordingly, under these conditions a corre
to an adjustable phase shifter 4I of any conven
sponding pulse will appear in the output which
maybe connected from terminals 13 to any de
sired utilizing device. It will be seen that by ad
justing the phase of the pulses from pulse gen
erator 38, by means of manual adjustment 42,
tional type, Whose phase shift is adapted to be
to be in phase coincidence with a desired re
noise Waves.
The pulse gate 36 includes a control voltage de
rived from control oscillator 39 that is conducted
controlled by manual control knob 42, This volt
ceived pulse, corresponding to a particular` re
flecting object or target, an output Wave will be
_generator 43 and thence to the pulse generator
derived at terminals 'I3 corresponding to this re
38. It will be clear that, by suitable adjustment
ilected pulse, but this output will remain entirely
of_ phase shifter 4I, the phase of the square wave 70 unaffected by any other pulses or any accom
age Wave is supplied to a suitable square wave
output of generator 43 and of the pulses of gen
erator 38 may be suitably adjusted with respect
panying noise Waves interspersed therebetween.
The gate 36, therefore, acts to permit passage
-to that ‘of control oscillator 39 ras desired. The
of a selected pulse determined by the setting of
>duration of the generated pulses is preferably
adjustment _42. Since these generated pulses are
substantially equal to that of the received pulses 75 of very short duration, as described above, con
2,408,821
5
the dropÁ across resistor 81. Hence, the grid bias
denser 69 is provided across output resistor 68 of>
tube 63, of a capacitance adapted to substantially
lengthen the pulses impressed on resistor 68.
of thev power tube 89,A as determined bythe
voltage drop across the resistorA 81, varies aptY
preciably to change the internal resistance of the
These lengthened output pulses represent the
average output level of the receiver.
'
The lengthened output of pulse gate 36 is fed
by a lead 15 to an automatic volume control cir
cuit which embodies the present invention.V The
lengthened pulses are supplied by the lead 15 to
C31
power tube.
-
'
This change in the resistance of the power
tube Yproduces a correspondingly appreciable
change in the voltage drop across it because a
corresponding to the average intensity of the
relatively large current continuously flows
through the power tube. Hence, the potential
supplied to the screen grids of the amplifying
pulses transmitted by the pulse gate 36. This
voltage corresponding to the average output of
the receiver is then applied to control grid 8| of
mediate frequency amplifier stages. By chang
a rectifier and ñlter circuit 16 to derive a voltage
a high gain control tube 82 shown as a pentode
whose cathode 83 is connected to a source 84 >of
low positive voltage providing a grid bias for the
control grid 8| of the control tubev 82. Anode 85
of the control tube 82 is connected in series with
a resistor 81 to cathode 88 of a power tube 89
shown in the drawing as a beam power tube. The
anode 9i of the power tube 89 is connected to a
source 92 of high positive voltage. The voltage
drop across the resistor V81 is supplied to control
grid 93 ofthe power tube 89 as by a lead 94.
In eiîect, the output of rectifier unit 16 con
trols the conductivity and hence the internal re
sistance of the control tube 82. In this manner,
the amount of current drawn from source 92 by
tubes by the lead 98 changes sufficiently .~ to
change the amplification of the .various linter
ing the ampliñcation of all of the intermediate
frequency amplifier tubes, a small change in the
output level of the receiver may, by eifecting even
a slight change in the voltage applied to the
various screen grids, effect a sufficient overall
change inthe amplification of the intermediate
frequency amplifier to maintain the output of the
receiver at a substantially constant level. Asis
apparent from the foregoing description, control
of the screen grids is accomplished by a voltage
divider circuit, one portion of which supplies the
high current that is drawn by the screen grids
while another portion of the voltage divider
draws a much smaller current but controls the
resistance of the íirst portion to change the am
the control tube 82 through the power tube 89 30 plification of the intermediate frequency ampli
fier.
and the resistor 81 is controlled by the intensity
As many changes could be made in the above
of the receiver output represented by pulses from
construction and many apparently widely differ
the pulse gate 38. Should this intensity vary
ent embodiments of this invention could be made
so as to decrease the internal resistance of the
control tube 82,.it will be clear that more cur 35 without departing from the scope thereof, it is
intended that all matter contained in the above
rent will now through the resistor 81 producing
description or shown in the accompanying draw
a larger bias on the control grid 93 of the power
ing shall be interpreted as illustrative and not in
tube 89 tending to oppose this changing of cur
a limiting sense.
rent by increasingthe resistance of the power
What is claimed is:
tube. Accordingly, the internal resistance of the 40
1. An automatic volume control system for a
power tube 89 will also change but in an opposite
signal receiver, comprising a voltage divider in
sense and an equilibrium condition will be
cluding a pair of electron discharge tubes ar
ranged in a series circuit, means responsive to
said receiver for oppositely changing the re
be the same as before the change in intensity '
sistances of said tubes according to the average
of the gated pulse. In the illustration used, the
output level of said receiver, and means for con
effective resistance of the control tube 82 was
trolling the amplification of said receiver ac
decreased and the effective resistance of the
cording to the voltage across one of said tubes.
power tube 89 was increased. In this case, the
2. An automatic volume control system for a
potential of the cathode of the power tube 89 is 50
signal receiver including a screen grid ampliñer,
lowered. It will be clear that an opposite change
comprising a voltage divider including a pair of
in pulse intensity will reverse the process and
electron discharge tubes arranged in a series
decrease the resistance of the power tube 89. In
circuit, means responsive to said receiver'for op
this way, the potential of the cathode of tube 89
positely changing the resistances of said tubes
will be changed according to the intensity of the i
according to the average output level of said re
gated pulses.
ceiver, and means for controlling the voltage of
In the circuit shown in the drawing, the
the screen grid of said amplifier according to the
cathode potential of the power tube is of a fairly
voltage across one of said tubes.
high positive value and, accordingly, may be used
3. An automatic volume control system for a
directly to energize the screen grids of the in 60
reached once more. However, the potential of
the cathode 38 of the power tube 89 will no longer
termediate frequency amplifier tubes.
For this purpose a lead 98 is connected from
signal receiver, comprising a voltage divider in
cluding a pair of electron discharge tubes ar
ranged in a series circuit, means responsive to
said receiver for changing the resistance of one
28 of the first stage and to a lead 99 which is 65 of said tubes according to the average output
level of said receiver, means for oppositely
connected similarly to the screen grids of the
changing the resistance of the other of said
other stages of the intermediate frequency ampli
tubes, and means for controlling the amplifica
fier 32.
f
'
tion of said receiver according to the voltage
The screen grids of the several amplifying
stages draw a relatively large current constantly 70 across said other tube.
4. An automatic volume control system for a
through the power tube 89 in addition to the
signal receiver, comprising a voltage divider in
current drawn by the control tube 82. The cur
cluding a pair of electron dischargetubes ar
rent drawn by the control tube 82 is relatively
ranged in a series circuit with a resistor between
small and has little eiîect on the potential drop
across the power tube 89 but a larger effect on 75 said tubes, means responsive to said receiver for
the cathode 88 of the power tube 89 to the lead
2S. which supplies potential to the screen grid
2,408,821
7
changing the resistance of one of said tubes
according to the average output level of said
receiver, means' for applying the voltage drop
average output level of said receiver, and means
for 'oppositely changingÄ the resistance of the
other of said tubes’.
across said resistor to the other of said. -tubes
to oppositely change the resistance thereof, and
means for controlling the amplification of said
receiver according to the voltage across one of
said tubes.
5. An automatic volume control system for a
signal receiver including a screen grid amplifier,
comprising a voltage divider including a pair of
electron discharge tubes arranged in a series
circuit with a resistor between said tubes, means
responsive to said receiver for changing the re
sistance of one of said tubes according to the’
average output level of said receiver, means for
applying the voltage drop across said resistor
to the other of said tubes for oppositely chang
ing the resistance thereof, and means for con
trolling the voltage of the screen grid of said ~
amplifier according to the voltage across said
other tube for controlling the amplification of
said amplifier to maintain the average output
level of said receiver substantially constant.
6. An automatic volume control system for a
receiver of radiant energy, said receiver includ
5
10. In an automatic volume control circuit for
a signal receiver, apparatus' for producing a.
voltage dependent upon- the average output level
of said receiver comprisingv a‘ pair of electron
discharge tubes, a resistor arranged in a series
circuit between said pair of tubes, means respon
sive to said receiver for changing the resistance
of one of said tubes according to the average
output level of said receiver, and means for
applying the` Voltage across said resistor to op
positely‘ change the resistance of the other of
said tubes.
11. An automatic volume control system for a.
signal receiver including a screen grid ampliiier,
comprising a source of potential, a power tube
forming a dropping resistor for connecting the
screen grid of said ampliiier to said source of
potential, and control means connected in series
with said power tube and responsive to the aver
age output level of the receiver for' controlling
the resistance of said power tube to change the
voltage applied to said screen grid in a manner
to stabilize the output of said receiver.
l2. In an automatic' volume' control system for
a signal receiver including a screen grid ampliñer,
ing a screen grid amplifier for deriving there
from the wave envelope of said energy, compris
ing means for producing a voltage correspond
a source of potential, a power tube forming a
ing to the average amplitude of said envelope, a 30 dropping resistor for connecting the screen grid
divider comprising the series-connected anode'
of said amplifier to said source, a control tube
cathode circuits of a pair of electron discharge
connected in series with said power tube, and
tubes and a resistor connected therebetween,
means responsive'to the average output of said
means for controlling the resistance of one of
said anode-cathode circuits in accordance with
said average voltage, means for controlling the
resistance of the other of said anode-cathode
circuits in accordance with the voltage drop
across said resistor, and means for applying the
Voltage drop across said resistor and said iirst
anode-cathode circuit in series to the screen grid
of said amplifier to control the amplification
thereof, whereby said wave envelope is main
tained substantially at constant amplitude.
'7. An automatic volume control circuit for a
receiver of radiant energy, said receiver includ
receiver for actuating said control tube'to change
the resistance of said power tube thereby chang
ing the voltage applied to said screen grid in a
manner to maintain the output of said receiver
substantially constant.
13. An’automatic volume control system for a
signal receiver, said receiver including an am
pliñer having a plurality ofV screen grid ampli
fying tubes, comprising a source of potential, a
power tube forming a dropping resistor for con
necting the screen grids of said amplifying tubes
to said source, and a control tube connected in
series with said> power tube and responsive to
.the average output of said receiver for control
ing a screen grid amplifier for deriving there
from the wave envelope of said energy, compris
ling the resistance of said power'tube thereby
ing means for producing a voltage corresponding
changing the voltage applied to said screen grids
to the average amplitude of said wave envelope, 50 in a manner to stabilize said output.
a voltage divider comprising the’series-connected
14. In an automatic volume control circuit for
anode-cathode circuits of a pair of electron dis
a signal receiver, apparatus for producing a volt
charge tubes and a resistor connected therebe
age dependent upon the average output level of
tween, means for controlling the potential dif
said receiver comprising a source of potential,
ference between said cathodes in accordance with
a power tube having its anode connected to said
said average voltage, and means for applying
source, and means for changing the resistance
said potential diii’erence to the screen grid of
of said tube to changethe potential of the cathode
said amplifier to control the'ampliñcation there
of, whereby said wave envelope is maintained
substantially at constant amplitude.
8. In an automatic volume control circuit for
a signal receiver, apparatus for producing a
voltage dependent upon the average output level
of said receiver comprising a; pair of electron dis
charge tubes arranged in a series circuit, and
means responsive to saidl receiver forv oppositely
changing the resistances of said tubesV accord
ing to the average output level of said receiver.
9. In an automatic volume control circuit for
a signal receiver, apparatus for producing a volt
age dependent upon the average output level of
said receiver comprising a` pair of electron dis
charge tubes arranged in‘ a series circuit; means
responsive to said receiver for changing the re
eistance ofone of said tubes according’to'the
thereof> according to changes in said output level,
said means comprising a control tube connected
in series with said power tube.
15. An automatic volume control system for
a receiver of radiant energy, said receiver includ
ing an amplifier for deriving therefrom the wave
envelope of said energy, comprising means'for
producing a voltage corresponding to the average
amplitude of said envelope, a divider` comprising
the series-connected anode-cathode circuits of a
pair of electron discharge tubes and a resistor
connected therebetween, means for controlling
the resistance of one of said anode-cathode cir
cuits in accordance with said average voltage,
means lfor controlling the resistance of the other
of said anode-cathodecircuits in’accordance with
the voltage drop across said resistor, and means
for applying- the voltage drop across said resistor
2,408,821
9
and said first anode-cathode circuit in series to
said amplifier to control the amplification there
of, whereby said wave envelope is maintained
substantially at constant amplitude.
16. An automatic Volume control circuit for a
receiver of radiant energy, said receiver includ
ing an ampliñer for deriving therefrom the wave
envelope of said energy, comprising means for
10
cathode circuits of a pair of electron discharge
tubes and a resistor connected therebetween,
means for controlling the potential difference
between said cathodes in accordance with said
average voltage, and means for applying said
potential difference to said ampliñer to control
the amplification thereof, whereby said wave en
velope is maintained substantially at constant
amplitude.
producing a voltage corresponding to the average
amplitude of said Wave envelope, a voltage di 10
vider comprising the series-connected anode
HORACE MYRL STEARNS.
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