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Патент USA US2408644

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Oct. l; 1946.
,
J. W.'HUFF
` 2,408,644
COMBINED ÀMPLITUD'E-MODULATION AND- FREQUENCY-MODULÁTION RECEIVER STAGE
I
v Filed'Jply 24, 1944
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ATTORNEYS
Patented Oct. 1, 1946
¿man .
" UNITED* STATES Il“EN'I"v ÓFFICE
CORIBINED ANIPLITUDE-MODULATION AND y
FREQUENCY - MODULATION
RECEIVER
STAGE
John W. H_ulî, Chicago, Ill., assigner, by mesne
assignments, to Belmont RadiofCorporation,
Chicago, Ill., a corporation of vIllinois
'
'
Application July 24, 1944,. Serial No. 546,298
7 claims. (erecto-,20),>
Y
1
`
y
A
.
operate as a frequency-modulation limiter. YThe
stage. also includes switch means operable ina
This invention relates to combined amplitude
modulation and frequency-modulation receiver
first position to establish the 'first-named circuit
connections and to connect the output circuit to
the amplitude modulation detector and operable
in a second position to establish rthe second
namedpcircuit connections and to connect the
output'circuit to the discriminator.
stages and to a receiver embodying the same and
particularly to a receiver of the type designed
with a view to maximum simplicity for market
ing in the lower price ranges.
In the prior art receivers designed for the re
ception of the standard broadcast band of ap
Also in _accordance with the invention, a wave
proximately 500-1500 kilocycles and the frequen
cy-modulation band of 41-50 megacycles, it has 10 signal receiver adaptedselectively to receive am
plitude-modulated signals or frequency-modu
been the practice to provide an amplitude-modu
lated signals comprises, in the order named, a
lation signal-transmitting channel including a
diode amplitude-modulation detector, a frequen
cy-m'odulationV signal-translating channel, at
least in part distinct from the amplitude-modu--
y15
lation channel and including one or more lim
iters followed by a frequency discriminator or
detector, and an'audio-frequency system selec
tively energized fromk the amplitude-modulation
radio-frequency selecting and converting means
for deriving from a selected received radio-fre
quency signal an intermediate frequency signal,
a dual-purpose signal-translating stage of the
type described,- and a signal-reproducing means
coupled to- the signal-frequency output circuit
of the stage. '
'
.
_
` For a rbetter understanding of the invention, to
channel or the frequency-modulation channel.
This> use of distinct amplitude-modulation and
gether‘,_w'ithv other and further objects thereof,
frequency-modulation channels increases` the
reference ` is" had to ythe following description
complexity and cost oi the receiver and has lim
taken in -connection n with the accompanying
drawing 'while'its scope will be pointed out in the
ited the lower price ranges within which thisy Atype
of receiver could be marketed.
'
25
` It is an object of the invention, therefore, to
provide a new and improved combined amplitude
appended claims.
.
y
Ä
n
vReferring now to the drawing, the single figure
is a circuit diagram, partly schematic, of a com-v
plete, superheterodyne receiver embodying the
modulation and frequency-modulation receiver
combined amplitude-modulation and frequency
stage for selectively effecting detection of a re
ceived amplitude-modulation signal or acting as 30 modulation receiver stage of the invention.
, Referring now to the single figure 'of the draw
ajlimiter for areceived _frequency-modulation`signal.
.
.
ing, there is represented, partially schematically,
.
the circuit :of a complete superheterodyne wave
It is another` object of the invention to provide
an improvedl receiver adapted selectively to re
ceive amplitude-modulated signals or frequency
signal receiver adapted selectively to receive am
35 plitude-modulated signals ' or frequency-modu
modulated'signals and including a combined am- `
plitude-modulation ' and
frequency-modulation
receiver stage of the type described, in order sub
stantially to reduce the complexity and cost of`
thev receiver.
In accordance with the invention, in a wave- 'i ‘
signal receiver4 adapted selectively to receive am
plitude-modulated signals orïfrequency-modu
lated signals, a dual-purpose signal-translating
stage comprises a vacuum tuber having a plurality
of electrodes, including a signal input electrode '
and a signal output electrode, and an input cir
’cuitior applying received signals to. the input
electrode. The stage also includes a. frequency
lated signals. This receiver comprises a. radio
frequency amplifying and selecting unit lll having
its input circuit connected Ato an antenna circuit
Il and its’output circuit connected to an oscil
lator _modulator- I2,these two units being effec
tive to.. derive from a selected received radio-fre
quency signal ~an intermediate-frequency signal
from either‘the amplitude-modulation range or
the frequency-modulation. range. The units l0
and i2 may be of conventional design with suit
able-range ` switches> Illa, l2a, respectively, for
selectively translatingV amplitude-modulated sig
n'alsv or-'frequency-modulated signals. The re
ceiver also includes an"intermediate-frequency
discriminator coupled to the output electrode of> 50 selector and amplifier, I3 coupled' to the oscillator
the vacuum tube, a signal-frequency output cir- "‘
modulator I2Ífor translating'the intermediate-'~
cuit, circuitconnections for the tube velectrodes
frequency'signal of either type. The unit I3 may
be,of-anyfsuitabletype and, as shown,v includesl
inï'its-y output circuit a composite tuned selector
to cause the tube to operate as a diode amplitude
modulation detector and other circuit connec
tions for the tube electrodes to cause the tube to
i4 comprising tuned primary and secondary cir
2,408,644
3
4
cuits Ma, Illb tuned to transmit the frequency
circuit 24 of the receiver. The switches 22 and
23 are >ganged for unicontrol with each other and
with the switches Illa, I2a of the units I0 and I2
modulated intermediate-frequency signal in se
ries with the primary and secondary tuned cir
cuits Mc, Iäd, respectively, tuned to the ampli
tude-modulation intermediate frequency. The
series impedance of each of the component tuned
by means of a mechanism indicated schematically
at U. The switch 22 is operable in its second or
FM position to remove the ground connection
from the screen and output electrodes of tube
circuits is negligible at the intermediate carrier
frequency to which it is not intended to respond
l5V and to restore the tube electrode connections
so that the tuned circuits eiîectively comprise an
to normal; that is, to establish the FM limiter
. circuit connections.
Simultaneously, the switch
automatic switching arrangement for selectively
10.
2‘3‘ inA its> secondr position is effective to connect
the output circuitv 24 to the terminal 2li of the
receiving either the amplitude-modulated or
the frequency-modulated intermediate-frequency
signals.
discriminator 2|y through a filter comprising a se
ries resistor 25v and shunt condensers 2|z- and 26.
The receiver also includes -a' dual-purpose sig
nal-translating stage comprising a vacuum tube
I5 having a plurality of electrodes, including a
signal input electrode or grid |5a andy `a signal
The values of the'resistor |'| and condenser I6
of the time-constant circuit are chosen to impart
a short time-constant of the order of 2 micro
secondsy to this circuit, which is necessary both
for good limiter action and for satisfactory am
output electrode or anode |5b. Specifically, the
tube is illustrated as of the pentode type includ
ing also »conventional screen and suppressor 20 plitude-modulation detection. The negative bias
developed across the circuit I6, |'| is applied as
electrodes. The secondary circuit of the selector
I 4 Vcomprises an input circuit for applying re
ceived intermediate-frequency signals to the in
put electrode I5a of tube l5 ‘and includes a time
an automatic ampliiication control bias to the
constant circuit such as a series condenser I6
shunted by a leak. or load resistor I1 therefor.
The anode |51) of tube I 5 and its screen are ener
gized from a suitable source indicated as +B
the AVC circuit, as indicated. ,
control electrodes of lone or more of the tubes in
cluded within the units I0, I2 and I3 by way of
The receiver also includes an audio-frequency
amplifier 2l coupled to the signal-output circuit
24 and having’an output circuit connected to a
signal reproducing means, such as a loud
through a dropping resistor I8 by-passed' to
ground >by means of a condenser I9 shunted by 30 speaker 28.
The. operation of the complete receiver illus
trated in the drawing will be readilyv understood
from the foregoing description. In brief, how
a resistor 20.
The receiver also includes a frequency dis
criminator 2| coupled to the output electrode
I 5b of tube l5. The discriminator may be of any
ever, the units I0 and I2 are effective to derive
conventional form but, as illustrated, comprises 35 from a signal picked up by the antenna circuit. I I
an intermediate-frequency signal having one
a primary tunedV circuit 2|a coupled to a sec
value of intermediate carrier frequency for fre
ondary tuned> circuit comprising an inductor 2lb
quency-modulated signals and a substantially dif
shunted by two series-connected condensers 2|c
and 2Id. The inductor 2lb is inductively cou
ferent, usually lower value, of intermediate car
pledto- the primary circuit 2|a and, as indicated 40 rier frequency for amplitude-modulated signals,
schematically, is adjustably tuned by means of a
as. determined. by the constants Aof the oscillator
circuit which are adjusted b-y operation of the
powdered. iron or-like ferro-magnetic core 2|Ic.
The high. signal-frequency-potential terminal of
switch I2a.
the circuit 2|a is connected to the~ junction be
When the switches |0a, |2a, 22 and 23 are oper
tween condensersZIc and 2|d. Terminals ofthe ' ated to» their right-hand positions for the recep
tion of frequency-modulated signals, the inter
secondary tunable. circuit 2lb, 2|c, 2|d are con
mediate-frequency signals derived therefrom. are
nected` to- diode rectiiiers 2|e and. 2| f shunted
selected by theportions Illa, Nb ofv selector I4
by load. resistors. 2Ig and 2I`h, respectively, the
and applied to the signal-input electrode of tube
cathode Yof the diode V2 If being grounded. and the
l5.V Due to thev self-biasing, action of the grid
cathodev of the diode 2|e being by-passed to
ground for intermediate-frequency signals
circuit of this tube, including the time-constant
through a condenser 2li. The signal-.frequency
circuit I6, I'I, and to the selection of its screen
and anode potentials, the tube I5 operates in a
output is derived from the terminal-2li of the
discriminator 2|.
With the circuit connections
forthe tube I5 as described, it operates as a con
conventional manner as a limiter to develop in
55
ventional frequency-modulation amplifier and
limiter.
The stage also includes circuit connections for
the' electrodes of tube l5 such. that it operates
its output circuit intermediate-frequency> signals
of substantially constant amplitude but >fre
quency-modulated in accordancewith the trans
mitted signal. This intermediate-frequency sig
nal 'is impressed upon the discriminator 2 |` which
tion to modify the normal tube electrode con
operates in a conventional manner to develop at
its terminal 2 la' a signal-frequency output. While
the operation of the discriminator 2| is conven
tional, its. circuit is not entirely conventional in
nections and~ to establish the amplitude-modula
tion detector circuit connections. Specifically,
circuit 2| b, 2Ic and 2|d at the junction between
with the time-constant circuit IB, l1 as an am
plitude-modulation detector. To this end there
is provided switch- means operable in its first posi
that the primary voltage is fed into the. secondary
this means comprises a two-position switch 22
the condensers 2|c -and 2id-...which effectively
comprise a voltage divider, rather than at a mid
effective-in its first position, as illustrated, to con
tap of the inductor 2lb as is conventional. This
nect the screen and output electrode or anode of
arrangementpermits the use of aninductor 2lb
tube I5 to ground, so that the input electrode |5_a
and cathode ci the tube I5 `function as a diode. 70 without an. electrical midpoint and therefore
adapted> for tuning by the. use of an. adjustable
amplitude-modulation- detector with the time
powderediron or other ferromagnetic core. Such
constan-t circuit I6, I‘I as its load circuit. There is
an arrangement has well known. improved fre
also vprovided a two-position switch 23 operable
in vitsíirst position, as illustrated, to connect the ~
time-constant circuit I6, |'| to a signal output 75
quency stability characteristics.
The signal-frequency output fromy the ter
2,408,644
5
minal 2 Iy“ is-passed through the'carrier frequency
~ filter 2 Iz','25,'26 and impressed through the switch
23 upon the audio-frequency ampliiier 21 from
which it is delivered to the loud speaker 28 for
reproduction.
i
-
.y
v
`
f
.
~ VOn the other hand, ifL the switchesy Iûa, I2a,
22 and 23 are operated to their-left-hand posi
6
electrodes to cause said tube to operate-asa Ifre
quency-modulation limiter, andv switch means
operable in a iirst position to establish said >iirst
>named circuit connections and to connect’said
output circuit to said time-constant circuit and
operable in a second position -to establishfsaid V
second-'named circuit connections and to connect
said output circuit to said discriminator.
tions; as illustrated in the drawing, an> inter
3. In a wave-signa1 receiver adapted selectively
, mediate-frequency `signal‘of lower carrier fre
10Y
to
receive amplitude-modulated signals or ire
quency is developedby unit I3 and `selectedin
quency-modulated signals, a dual-purpose signal
portions I4c, I4dbf selector 'I4 and impressed
. upon the signal-input electrode'v I 5a of Y-tube I5.
With this connection, the screen and anode elec
trodes of tube I5 are effectively grounded so that
- the vgrid and cathode of '.this'tubei- operate With 15
.
translating stage comprising, a vacuum tube hav
ing a plurality of electrodes including a signal
input electrode and a signa1 output electrode,` an
input circuit for applying >received signals to said
input electrode including a series condenser and
the time-constant circuit I6; I1 as a'conventional
a leak >resistor therefor, a frequency. discriminator
diode peak detector, developing a’ signal-fre
coupled to said output electrode, a signal-fre
quency output across the time-constant circuit
quency
output circuit, circuit connections for said
This
output
is
impressed
through
the
I6, I1.
switch 23 upon the audio-frequency ampliiier 20 tube electrodes to cause "said tube to operate with
said time-constant circuit as a diode amplitude
21 from which it is delivered to the loud speaker
modulation detector,l circuit connections for said
28 for reproduction. '
'
l
tube electrodes to cause said tube to operate as
As is well understood in the art, the AVC con
a frequency-modulation limiter, andA switch
nection from the time-constant circuit I6, I1 is
effective to impress upon the control electrodes 25 means'operable ina iirst position to establish said
iirst-named circuit connections and to connect
-of the tubes of the units I Il,ï I2 'and I3 a nega
said output circuit to said condenser and operable
tive bias potential proportional tothe average
in a' second position to establish said second
intensity of the received carrier signal and thusV
named circuit connections and to connect said
to control the amplification in these units in
Suche. Way as to maintain the amplitude of the 30 output circuit to said discriminator.
4. In a wave-signa1 receiver adapted selectively
signal input to detector I5 within a narrow range
to
receive amplitude-modulated signals or fre
for a wide range of received signal intensities.V
quency-modulated signals, a dual-purpose signal
While there has been described what is at
translating stage comprising, a vacuum tube hav
present considered to be the preferred embodi
ing a plurality of velectrodes including a signal
35
ment of the invention, it will be apparent to
input electrode and a signal output electrode, an
those skilled in the art that various changes and
input circuit for applying received signals to said
modifications may be made therein without de
input electrode including a time-constant circuit,
parting from the spirit or scope of the inven
a frequency discriminator coupled to said output
tion.
40 electrode, a signal-frequency output circuit, said
I claim:
tube electrodes normally being connected to op
l. In a wave-signal receiver adapted selectively
erate as a frequency-modulation limiter, and
to receive amplitude-modulated signals or fre
switch means operable in a first position to
quency-modulated signals, a dual-purpose sig
modify said tube electrode connections to cause
nal-translating stage comprising, a vacuum tube
having a plurality of electrodes includin-g a sig 45 said tube to operate with said time-constant cir
cuit as a diode amplitude-modulation detector
nal input electrode and a signal output electrode,
and for connecting said output circuit to said
an input circuit for applying received signals to
time-constant circuit and operable in a second
said input electrode, a frequency discriminator
position to restore said tube electrode connections
coupled to said o-utput electrode, a signa1-fre
quency output circuit, circuit connections for said 50 to norma1 and to connect said output circuit to
said discriminator.
tube electrodes to cause said tube to operate as
5. In a wave-signal receiver adapted selectively
a diode amplitude-modulation detector, circuit
to receive amplitude-modulated signals or fre-V
connections for said tube electrodes to cause said
quency-modulated signals, a dual-purpose signal
tube to operate a's a frequency-modulation lim
iter, and switch means operable in a iirst posi 55 translating stage comprising, a vacuum tube hav
ing a plurality of electrodes including a signal
tion to establish said ñrst-named circuit con-V
input electrode and a signa1 output electrode, an
nections and to connect said output circuit to
input circuit for applying received signals to said
said amplitude-modulation detector circuit and
input electrode including a time-constant circuit,
operable in a second position toV establish said
second-named circuit connections and to connect 60 a frequency discriminator coupled to said output
electrode, a signal-frequency output circuit, said
said output circuit to said discriminator.
tube electrodes normally being connected to op
2. In a wave-signal receiver adapted selec
erate as a frequency-modulation limiter, and
tively to receive amplitude-modulated signals or
switch means operable in a ñrst position to con
frequency-modulated signals, a dual-purpose
signal-translating stage comprising, a vacuum 65 nect said signal output electrode to ground to
cause said tube to operate with said time-constant
tube having a plurality of electrodes including
circuit as a diode amplitude-modulation detector
a signal input electrode and a signal output
and for connecting said output circuit to said
electrode, an input circuit for applying received
time-constant
circuit and operable in a second
signals to said input electrode including a time
constant circuit, a frequency discriminator cou 70 position to restore said tube electrode connections
to normal and to connect said output circuit to
pled -to said output electrode, a signal-frequency
said discriminator.
output circuit, circuit connections for said tube
6. A wave-signal receiver adapted selectively to
electrodes to cause said tube to operate with said
receive
amplitude-modulated signals or fre
time-constant circuit as a diode amplitude-mod
ulation detector, circuit connections for said tube 75 quency-modulated signals comprising, a radio
2,408,644
7
frequencyselecting Vvandxconverting means for- de..
riving' from a- selected receiveclradio-i‘requency
signal an intermediate-frequency signal, a dual
purpose` signal-translating stage including a Vac
uum tube -having'a plurality of electrodes includ
ingza signal input electrode and a signaloutput
8
riving2 from a: selectedA received radio-frequency
signal an intermediate-frequency signal, a‘dual
purpose ysignal-translatingstage including a vac
uum tube having a plurality of electrodes includ
ing a signal input electrode and a signal output
electrode, an input circuit for applying received
electrode, an input circuit'for applying received
signals to said input electrode including a time
signals to said input electrodev including a time
constant circuit, a frequency discriminator cou
constant circuit, a frequency discriminator'cou
pled to said output electrode, a signal-frequency
pled to. said output electrode;` a. signal-frequency l0 output circuit, circuit connections for said tube
output circuit, circuit connections for saidtube
electrodes to cause said tube to operate with said
electrodes to cause` said tube -to- operate »with said
time-constant circuit as a diode amplitude-modu- `
time-constant circuit as a diode amplitude-modu
lationdetector, circuit connections for said tube
lation detector, circuit connectionsI for said tube
electrodes toA cause said tube to operate as a fre
electrodes to cause ysaid tube-to operate as a fre
fluency-modulation limiter, and switch means-op
erable in-a ñrst position to’establish said iirst
15 quency-modulation limiter, and switch means op
erable in a ñrst position to establish said first
named circuit connections and to connect said
output circuit to said time-constant circuit and
operable in‘a second position to establish said_
operable in a second’position to establish said 20 second-named circuit connections and to connect
‘second-named circuit connections and to connect
said output circuit to said discriminator, switch
said output circuit to said discriminator, anda
means included in said selecting and converting
signal-reproducing means coupled 4to saidoutput
means for selecting signals from the amplitude
circuit.
modulation range or the >frequency-modulation
7. A Wave-signal receiver adapted selectively to 25 range, unicontrol operating means for both of
receive- amplitude-modulated »signals or fre
said switch mean‘s, and a signal-reproducing
quency-modulated signals comprising, a radio
means coupled to said output circuit.
frequency selecting and converting means- for de
JOHN Wa HUFF.
named circuit connections and to connect said
output circuit to said time-constant-circuit and
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