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Патент USA US2412482

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Patented Dec. 10, 1946
‘2,412,482
UNITED STATES PATENT OFFICE
2,412,482
DISCRIMINATOR-RECTIFIER CIRCUITS
Benjamin S. Vilkomerson, Camden, N. 3., assign
or to Radio Corporation of America, a corpora
tion of Delaware
Application August 10, 1944, Serial No. 548,854
8 Claims. (Cl. 250-27)
1
2
My present invention relates to discriminator
recti?er circuits for frequency-variable waves,
and more particularly to novel and improved fre
quency modulation (FM) detector circuits.
The well known discriminator-recti?er circuit
of the type disclosed and claimed by S. W. Seeley
in U. S. Patent No. 2,121,103, granted, June 21,
1938, employs a center-tapped secondary coil for
the input transformer of the opposed signal rec
ti?ers. This center-tapping is disadvantageous
to the employment of inductance tuning by a
relatively movable core, because the core, usually
method of operation will best be understood by
reference to the following description, taken- in
connection with the drawings, in which I have
indicated diagrammatically several illustrative
of comminuted iron, entering one end of the sec
ondary coil causes the inductances of the two
circuits whereby my invention may be carried
into e?ect.
In the drawings:
Fig. 1 shows an embodiment of the invention
as applied to a discriminator section of the gen;
eral type shown in the aforesaid Koch applica
tion;
Figs. 2 and’ 3 show respectively different mod
i?cations employing a discriminator section of
the type disclosed in the aforesaid Seeley patent;
halves of the secondary to be unequal. Further 15 and
more, a radio frequency choke coil is employed
Fig. 4 shows a further modi?cation employing
a multi-purpose tube.
in the patented circuit from the center-tapping
Referring now to the accompanying drawings,
point on the secondary to the recti?er load cir
wherein like reference characters in the different
cuit. In his application Serial No. 529,074, ?led
April 1, 1944, W. R. Koch has disclosed and 20 ?gures designate similar elements, I have shown
claimed a highly effective circuit'arrangement
only so much of the circuits of an FM receiver
functioning in like manner to the aforesaid
Seeley discriminator circuit, and providing an im
proved form of FM wave discriminator-detector
circuit employing a minimum number of circuit
system as is essential to a proper understanding
of the invention. The discriminator-recti?er
network of my present invention is not restricted
, in its utility to FM reception, however, since it
may be employed to provide automatic frequency
An important object of my invention is to pro
control (AFC) voltage for thelocal oscillator of a
vide an improved form of frequency modulation
superheterodyne receiver of amplitude modula
discriminator-detector circuit, which may be of
tion (AM) carrier waves. The aforesaid Seeley
the type disclosed and claimed in said Koch ap 30 patent shows the manner of this utilization of
plication, which is well-suited for inductance
the invention. My circuit is, also, adapted to
tuning of the input transformer windings al
detect phase modulated (PM) waves. The par
ticular frequency ranges or speci?ed operating
though-not limited thereto, and which employs'a
pair of diode recti?ers' with common grounded
frequencies referred to hereinafter are to be un
electron emitters.
derstood as being purely illustrative. Further,
A more speci?c object of my invention is to
the generic term “angle modulated carrier wave”
provide a novel arrangement of the diode
as used herein is to be understood as including
recti?ers in a discriminator-recti?er network,
a frequency modulated carrier wave, a phase
whether the discriminator-detector circuits are of
modulated carrier wave or related forms of mod
the type shown in the aforesaid Seeley patent or
ulated carrier waves. Those skilled in the art
that shown in the Koch application, each recti?er
of radio communication know that an FM wave
having its space current path directly shunted by
is produced by varying the carrier wave relative
its respective load resistor, and there being a
to its mean frequency to an extent proportional
common direct connection between the recti?er
to the amplitude of the modulating frequency,
electron emission surfaces and ground whereby 45 and a PM wave differs in having a frequency
the circuit is especially suitable for use with ?la
deviation which increases with modulating fre
components.
mentary cathodes in battery-operated receivers,
with the indirectly-heated cathode of the double
diode type of tube, or with the multi-purpose type
quency. The above generic expression “angle
modulated”‘is, also, intended to include a modu
lated wave of constant amplitude wherein the
of tube having a common cathode and including 50 modulation is neither pure FM nor pure PM, but
two diode plates.
contains common components and is, therefore,
The novel features which I believe to be char
a hybrid modulation.
acteristic of my invention are set forth with par
My present improved discriminator-recti?er
ticularity in the appended claims; the invention
circuits may be embodied in various well-known
itself, however,‘ as to‘ both/its organization and 55 forms of receivers. For» example, they may be
2,412,482
3
struction are fully acquainted with the manner of
adjusting the inductance value of a coil by
employed in a superheterodyne receiver adapted
to be operated in the presently-assigned FM band
means of an adjustable iron core.
of 42-50 megacycles (mc.) , and it is to be under
FM waves, which according to present standards
of FM broadcasting may have a frequency devia
tion up to a maximum of 75 kilocycles (kc.) on
either side of the transmitter carrier frequency,
are collected by the signal collector device, and,
after selective radio frequency ampli?cation if
desired, are converted to an intermediate fre
quency (I. F.) by any suitable conversion means.
Any desired operating 1. F. value may be used
such as, for example, 4.3 me. After selective
I. F. ampli?cation the FM energy, having a mean
or center frequency of 4.3 mc., may be subjected
to amplitude limiting in order to remove any am
plitude modulation which may have arisen during
the course of propagation and reception of the
waves.
adjust the inductance value of coil I, while nu
meral 1 indicates the corresponding adjustable
iron core for selecting the inductance value of
coil 2’, 2". In general, the iron plugs or trim
mers E and ‘I will be individually adjusted so that
each of the primary and secondary circuits is
tuned to the operating I. F. value, which has
been stated, by way of example, as being 4.3 mo.
Coil 2’, 2” may have its inductance selected so
as to be double the inductance value of coil l at
the normal resonant condition of the two circuits
including them. The condensers 8 and 9 are
chosen equal in magnitude. These are only illus
trative constants. With suitable values for the
condenser elements 8 and 9, the inductance of
20 coil 2', 2” at twice the value of the inductance
of coil I will provide a resonant frequency for
Referring to Fig. 1, the primary winding or coil
I derives FM waves from any suitable FM wave
source. The coil may be connected in the plate
circuit of the ?nal I. F. ampli?er tube or the
amplitude modulation limiter tube 3 of a super
heterodyne receiver. A condenser 2 is connected
in shunt with coil l to provide the primary reso
nant circuit of the discriminator network. The
upper end of coil I is to be understood as being
connected to the plate of the prior signal trans
mission tube, for example, the amplitude'limiter
3, whereas the lower end of the coil I is connected
to the usual +B terminal of a suitable direct
current energizing source. The limiter 3 may r
be of any well-known form, so long as the “input
vs. output” characteristic thereof approximates
the idealized form shown in Fig. 1 directly above
the schematic box 3. The input transformer T
is constructed to respond to a band of frequencies 40
at least 200 kc. wide so as to provide suitable
tolerances for passing the maximum frequency
swing of the received FM waves. This is, also,
true of the selector circuits prior to input trans
former T.
The numeral
6 designates the iron core or plug adapted to
stood that the networks prior to transformer l, 2’,
2" of Fig. 1 are of well-known construction. The
'
the secondary circuit which is substantially equal
to the resonant frequency of the primary circuit.
Unlike the aforesaid discriminator circuit of
the Seeley patent, the high alternating potential
side of primary circuit I, 2 is connected by lead
H to the junction of condensers 8 and 9. This
will result in establishing the junction point H
‘at the same alternating potential as the high
alternating potential side of the primary circuit.
At the same time each of condensers 8 and 9
will function as a direct current blocking con
denser to prevent application of +13 voltage to
the opposed rectifiers D and D’. The condensers
8 and 9 offer a relatively low impedance to the
I. F. voltage at the primary so that substantially
the full value of primary voltage is applied to
the respective diode anodes l2 and I3. The rec
ti?ers D and D’ are shown by way of example
as diodes having their electrodes embodied in a
common tube envelope.
This invention is not limited to a tube con
taining but two diode sections in a single en
velope. It is to be understood that numerals ill
and i5 of Fig. 1 merely designate in schematic
The output transformer l, 2’, 2” also is pro
manner a pair of separate electron emission sur
vided with a pass band width of 200 kc. The
damping resistor R may be provided across the
resonant primary circuit 2, l to insure a su?icient
faces for respective anodes l2 and [3. The emis
sion surfaces may be separate cathodes, as of the
ly broad pass band. The +B lead is bypassed
to ground for intermediate frequency currents by
condenser ll. The secondary coil is divided into
may be separate portions of a common cathode;
they may be the common cathode, ?lamentary
or indirectly heated, of a multi-purpose tube
having two diode plates and a separate triode
two sections 2’ and 2", both of which are mag
netically coupled to coil l as indicated by brackets
M and M1. The secondary winding may be di-.
vided into the two sections 2’ and 2" in any
suitable manner. As shown, the condenser 5 is
inserted between the inner ends of sections 2’
and 2" so that condenser 5 effectively separates
the latter. Sections 2' and 2" are preferably 60
of equal value thereby reducing the required ef
fectiveness of choke coils 23 and 24. The con
denser 5 is an isolation condenser, and acts to
bypass I. F. currents to which it has a relatively
low impedance. Condenser 5 may have a value,
for example, of 200 micromicrofarads, and blocks
audio frequency as well as direct currents. The
coil 2’, 2” is shunted by condensers 8 and 9 con
nected in series. The condensers 8 and 9 provide
resonating capacitance for the discriminator sec
ondary circuit. Thus, circuit 2', 2", 5, 8, 9 is
, the resonant secondary circuit of the discrimina
tor network. Each of coils l and 2', 2” is pref
erably of the inductance tuner type.
Those skilled in the art of radio receiver con
directly-heated or indirectly-heated types; they
or pentode section. In any of these instances
the two diodes will have electron emission sur
faces connected in common to ground. Let it be
assumed that in Fig. 1 the cathodes l4 and 15
are separate portions of a common cathode, as in
a 6SQ'7 or 1F6 type tube, and that the grid and
plate of the triode section are grounded and in
effective. The two diode sections are shown
as separate, however, so as to make it clear that
the GHG type of tube can also be used.
The anode l2 of diode D is connected to one of
the terminals of condenser B and to the upper end
of coil section 2', whereas the anode l 3 of diode D’
is connected to one of the terminals of condenser
9 and to the lower end of coil section 2". The
other terminals of condensers 8 and 9 are con
nected together. Unlike in the Koch application,
the electron emission surfaces l4 and I 5 of the
diodes D and D’ respectively are directly con
nected together and to ground. Numeral l6 desig
nates the load resistor operatively associated with
recti?er D and connected directly in shunt with
'
"time
5
6
the space current path of the diode. Similarly,
load resistor I1 is connected directly between the
circuits there will be no alternating current cute
anode and cathode of its diode D’, and is, there
fore, directly in shunt with the space current path
,Assume, now, that at some later time the I. F‘.
signal energy has'a frequency different from the
predetermined mean frequency of the applied
waves, which is also the ‘predetermined frequency
of the primary and secondary circuits of the dis
Cl
of that diode.
There will ‘be developed across each of resistors
l5 and i? respective voltages produced by recti
put from the triode sections of tube I8.
‘
?cation of I. F. signal currents. t will be noted
criminator transformer. There will now ‘occur a
that the recti?ed voltages developed across re
phase shift in vthe signal energy ‘transmitted
sistors l t and H will not be added in polarity op 10 through the tuned transformer which is greater or
position as in the Koch application, since the an
less than 90°, dependingupon the direction and
ode ends of resistors id and l? are isolated by
extent of the difference between the frequency of
condenser E. The cathode terminals of resistors
i6 and ii are grounded, and recti?ed voltages of
negative polarity (to ground) are separately taken
from the anode ends of resistors l5 and ill.
The modulation or audio frequency components of
the rectified voltages are utilized by the network
shown in the drawings.
7
The audio frequency ampli?er tube i8 is shown
as a twin trio-dc tube, say one of the SEN’? type by
way of specific illustration. Separate triode tubes
may be employed if desired. The common cath
ode connection of tube 83 is connected to ground
by the bias resistor it, while control grids 253 and
2! are connected to opposite ends of the shunt ad
justable volume control resistor 22. Grid 2t‘ is
connected to the lower end of coil section 2'
through I. F, choke coil 23, while the adjoining end
of coil section 2” is connected to grid 2! through
I. F. choke coil 2%, v
The condensers
and 26 each function to b‘ -
the applied signal energy'and the predetermined
resonant frequency of the tuned primary and
secondary circuits. The signal energy transmitted
in parallel through condensers 3 and ‘9 will have
suffered no relative phase shift due to the non-se
lective phase-shift character thereof. 1 That is to
say, the signal energy applied through condensers
8 and 9 t0 the anodes l2 and 13 suffers‘no phase
shift which need be taken into account, whereas
the signal energy transmitted through the dis
criminator transformer undergoes a variable
phase shift from the normal quadrature phase
relation depending upon the direction and amount
of frequency deviation of the signal energy with
respect to the carrier frequency.
This means that there will be applied to the
anodes i2 and‘ i3 resultant signal voltages of dif
ferent magnitudes, as is well-known to those
skilled in the art. Hence, the recti?ed voltages
across resistors l5 and I‘! will be of different mag
nitudes, and the negative voltages at the anode
pass to ground any I. F. currents which get
end of each of resistors l6 and l? will be of rela
through choke coils 23 and 213. The plates 2? and
28 are connected to the opposite ends of primary 35 tive magnitudes dependent upon the extent and
winding 28 of output transformer
The center
tap on Winding Ed is connected to the +13 voltage
supply lead. The control grids 2E‘! and 2i are,
therefore, connected in push-pull relation to the
output resistors is and il‘, while the plates 2? and 40
sense of frequency deviation of the signal energy
with respect to the predetermined mean fre
quency. The relatively rapid frequency variation
28 are also connected in push-pull relation. The
of the signal energy corresponds to the modu
lation voltage which is transmitted on through
each of choke coils 23 and 2d.
direct current return paths for grids 23 and 25
‘are respectively through resistors 55 and ii.
In order clearly to present the advantages of
discriminator-detector circuit in which both di
ode electron emitters It and i 5 are grounded.
It will now be seen that I have provided an FM
the present improvement, the manner of operation '1; This is of advantage in the case of a receiver
using ?lamentary cathode tubes, as in the case of
of they circuit will now be explained. Let it ?rst be
assumed that the PM energy applied to the pri
battery-operated sets. Although cathodes l4 and
mary circuit l, 2 is at the mean or carrier fro
quency of 4.3 me. The condensers 8 and Q through
which signal energy is fed to each of anodes l2 :
15 are connected to a common ground point, the
diodes are effectively isolated for direct currents.
Thus, the direct current circuit for each diode is
traced as follows: From anode l2 through‘resistor
it, to cathode M and thence to ground; and from
and 53 are of low reactance values, and any phase
shift of the I. F. signal energy produced by them
will be negligible. Further, the signal energies
applied through condensers t and 9 will be of
like polarity. However, the anodes l2 and I3 are, i
also, connected to the opposite ends of coil sec
tions 2’, 2", Due to the magnetic coupling :be
tween the discriminator tuned circuits there will
occur a 90° phase shift at the carrier frequency.
Hence, the signal energy will be applied to anodes
l2 and fit from respective ends of coil sections 2’
and 2” in opposite polarity, but in each case in
phase quadrature with the signal energy at the
high potential side of the primary circuit. It fol
lows, therefore, that the resultant signal voltages
anode 13, through resistor 11, to cathode l5 and
ground. Alternatively, resistors l6 and It could
be omitted, and the series resistors 41! and so
could be employed between grids 2i! and 2!, the
junction of the resistors being grounded. The di
rect current path for each diode recti?er would
be in that case: From anode 12 through coil sec
tion 2', choke 23 and resistor iii! to ground. Sim
ilarly, there eXists a path from anode :3 through
coil section 2", choke 24 and resistor 56 to ground.
If desired the source of the recti?ed voltage may
be considered the successive negative charges
placed on the right hand sides of each of con
densers 8 and 9 during signal reception by the
unidirectional conductivity of the two diodes. It
is the leaking off of these accumulated negative
charges through load resistors it and H, or al
ternatively through resistors 49 and 56 if they
are used, and the recharging by the received sig
nal which supplies the direct current and audio
frequency output of the discriminator rectifiers.
While resistors fill and 58 are shown in Fig. 1
effectively applied to anodes i2 and it will be
equal at the carrier frequency, and the recti?ed
voltages developed across respective resistors 15
and I1 will be of equal magnitude. Since these
recti?ed voltages are separately applied to respec
tive grids 2i) and 2| in like negative polarity rela
tive to ground, the result will be that when the
signal energy is at the predetermined reference
frequency of each of the primary and secondary 75 since they do not'substantially affect the ope-‘ra
2,412,482
7
tion of the circuit, they may be preferably omitted
if resistors I6 and H are used.
The I. F. currents ?ow through each diode cir
cuit in the following manner: The I. F. voltage
produced across the primary circuit I, 2 by the
limiter 3 is combined in series with one-half the
voltage induced in each of sections 2' and 2",
and is impressed across each diode and ground.
8
tube‘ I8, and the limiter 3 saturating on a small
voltage, there is no need for guarding against cut~
off of each triode grid by the respective negative
voltages produced by the recti?ers. However, if
the output of the limiter 3 is high and/or the tri
odes have high ampli?cation factors, the nega
tive voltages produced by diodes D and D’ may
be high enough to cut off the plate currents of the
pair of triodes. Respective direct current block
flows from the high potential side of circuit I, 2 10 ing, condensers may be inserted, in such case,
in series in each side of the line to resistors 40
through lead I0 and condenser 8, through diode
In the case of diode section D the I. F. current
and 50. This is, also true for the circuits of Figs.
D to ground, and back through condenser 4 to
2 and 3.
the primary circuit I, 2. In the case of diode sec
As stated heretofore, the discriminator section
tion D’ the I. F. current from the primary cir
cuit I, 2 ?ows through condenser 9, through diode 15 may be that of the Seeley patent. In Fig. 2 I
have shown a modi?cation wherein the primary
D’, and returns through ground and condenser 4
circuit I, 2 has its high potential side connected
to the primary circuit.
by the direct current blocking condenser 8’ to
Adjusting the core ‘I will, unless the coils are
the midpoint of secondary coil 60. The con
especially designed to prevent it, affect the rela
denser 6I shunted across coil 60 tunes the sec—
20
tive inductive magnitudes of coil sections 2’ and
ondary circuit to the same I. F. value as primary
2", but chokes 23 and 24, by isolating the ground
circuit I, 2. The anodes I2 and I3 of diode sec
point from the coil sections at intermediate fre
tions D and D’ are connected to opposite ends of
quency, make this unbalance of no consequence.
coil 60 through respective condensers 62 and 63.
The voltage still divides across the two diodes D
and D’ in accordance with their respective im 25 The electron emission surfaces I4 and I5 are con
pedances. Chokes 23 and 24 can be eliminated
and the balance maintained if core ‘I is replaced
with a variable tuning condenser connected
across the outside ends of coil sections 2' and 2",
i. e., in parallel with condensers 8 and 9 in se
ries. The use of core Bis optional since the tuning
of the primary circuit is not very critical. If the
values of the inductance of coil I and capaci
tance of condenser 2 are kept to close tolerances,
nected in common to ground as in the case of
Fig. 1;
The anode I2 is connected to ground through
a path consisting of resistors 64 and 40 in series.
The anode I3 is connected to ground through a
path consisting of resistors 65 and 50 in series.
Instead of using the twin-triode type of tube I8,
separate triodes I8’ and I8" are used as the
audio frequency ampli?ers. The variable re
adjustable tuning may be dispensed with. How 35 sistor 22 is, again, connected in series between
the input grids of the audio frequency ampli?er
ever, it may be more economical to use wide-tol
erance components and tune the primary circuit
with core 6.
The present circuit is well suited for use with
sections and functions as a manual volume con
trol device. Each of resistors 64 and 65 may have
a magnitude of 10,000 ohms, and may function
?lamentary cathode tubes. With heater-cathode 40 as an I. F. choke, or as a substantial portion of
the load resistor of respective diodes D and D’.
type tubes there is eliminated the possibility of
The right hand end of each of resistors 64 and
audio frequency hum caused by heater-cathode
65 is bypassed to ground by respective condensers
leakage in the “high” diode. By “high” diode is
64' and 65'.
meant the type of discriminator wherein one di
Where the resistors 64 and 65 function as I. F.
ode has its cathode at ground potential, and the 4.
choke elements, then resistors 40 and 50, each
other diode cathode is at a high audio and direct
of which may have a magnitude of 0.25 megohm,
current potential to ground but is bypassed to
will function as the load resistor elements of
ground for radio frequency currents only. If the
respective diodes D and D’. In the modi?cation
radio frequency bypass condenser is too large, it
of Fig. 2 there is provided across each half of
will also bypass a portion of the audio output of
the discriminator. My present invention makes
feasible the use of a standard duo-diode common
coil 60 the resultant vector voltage of the primary
signal voltage and one-half the signal voltage
induced from the primary, as was explained in
connection with Fig. 1 and as is Well known to
those skilled in the art. The resultant vector
voltages applied to anodes I2 and I3 are equal
at thereference frequency of the discriminator
purpose tube having a common cathode and in
circuits. However, the voltages will vary in ac
cluding two diode plates. Such tubes currently
cordance with the sense and magnitude 0f fre
include an additional triode or pentode section
which utilize a common cathode, as depicted in 60 quency variation from the reference frequency.
As a result, the recti?ed voltages (relative to
' Fig. 4 of this application. The triode section or
ground) at the upper end of load resistor 40 and
pentode section may be used for other functions,
the lower end of load resistor 50 respectively will
or may be rendered ineffective. Furthermore, the
vary in accordance with frequency variation of
symmetry of the present discriminator network
the applied signal energy, as hereinbefore ex
to ground should give better radio frequency bal
plained.
ance. The audio frequency signals feed a push
The modification of Fig. 3 differs from that
pull ampli?er in the present circuit thereby elim
shown in Fig. 2 only in that the diodes D and D’
inating the need of a phase inverter tube, as is
use individual load resistors I6 and I‘! as in the
required for push-pull operation in the case where
the differential resultant voltage of resistors I6 70 case of Fig. 1. The resistors 64 and 65 function
solely as I. F. chokes. The resistors 40 and 50
and I‘! is used. In Fig. 4, described hereinafter,
of Fig. 2 are omitted, since they are unnecessary
I have, however, shown a method of utilizing the
because the control grids of triodes I8’ and I8”
triode section of a duo-diode triode tube as an
return to ground through respective paths 64, I6
audio ampli?er fed from the single-ended output
of the pair of recti?ers. Both low mu triodes in 75 and. I1, 65. It will be understood that the cir
cathode (grounded) tube in a frequency discrimi
nator circuit.
A most important advantage of this circuit ar
rangement is that it permits the use of a multi
9
2,412,482,
cult of Fig. 3 functions substantially in the same
manner as in Fig. 2,"except that the load re
sistors of the diode recti?ers in Fig. 3 are closer
in their circuit connections to those provided in
Fig. 1. It will be clearly understood that in each
of Figs. 1, 2 and 3 the diode sections D and D’
may be provided by a common cathode provided
with a pair of separate anodes as suggested in
10
circuit to the junction of said pair of condensers,
a ?rst diode recti?er having its anode connected
to one end of said coil, a second diode recti?er
having its anode connected to the opposite end
of said coil, an isolation condenser interposed
between sections of said coil, a ?rst load resistor
connected in shunt to one or" said recti?ers, a
second load resistor connected in shunt with the
second recti?er, means for establishing the oath
the modi?cation of Fig. 4. '
In the arrangement of Fig. 4 I have shown a 10 .c-de ends of both of said load resistors at ground
potential, and a separate recti?ed voltage utiliz
modi?cation of the arrangement of Fig. 3, where
ing means connected to the anode end of each
in the triode section of the detector tube is uti
load resistor.
‘
lized as a single-ended audio frequency ampli?er
_ 2. In a frequency discriminator system, a ?rst
for the audio output of the opposed diode recti
, circuit comprising a coil and a condenser tuned
?ers. It will be understood that the opposed rec
to a predetermined signal frequency, a second
ti?ers and their discriminator input circuit are
substantially the same as in Fig. 3. The multi
circuit comprising asecond coil shunted by a
pair of series-arranged capacitors, the second
purpose tube ‘It, which may be a GSQ'? type tube,
circuit being tuned to said predetermined fre
has its common cathode ‘H at ground potential
whereas the anodes I2’ and 13’ are connected to 20 quency, adirect connection from one side of the
?rst tuned circuit to the junction of said two
the high potential ends of respective load re
capacitors, a direct current blocking condenser
sistors l6 and H. A center-tapped audio fre
in a series circuit between two sections of said
quency reactor '52 has one end thereof connected
second coil, a pair of diodes, each diode having
through an I. F. choke coil 13 to the anode it’,
its anode connected to a‘respective end of the
while the choke coil ‘l4 connects the anode E2’
second coil, separate resistors respectively shunt
to the opposite end of reactor ‘H.
ing said diodes, means grounding the cathodes
The center tap of reactor 12 is grounded, and
the end of the reactor connected to choke ‘i3 is
of both diodes, and modulation utilization circuitsv
connected to the opposite sides of the blocking
connected to ground through the resistor 75 of a
volume control device whose adjustable tap 16 is
condenser.
23. In combination, a parallel resonant circuit
connected through audio frequency coupling con
tuned to a predetermined signal frequency, a coil
denser l'i‘ to the control grid 18. The resistor 79
returns grid 78 to ground, and the plate 58 of
tube ‘H3 is connected to a suitable point of posi
magnetically coupled to said parallel resonant
circuit, a pairof condensers connected in series
tive potential +B through plate’ resistor 34. It
elation across said coil and cooperating with the
latter to provide a second parallel resonant cir
cuit tuned to said predetermined frequency, a
connection between one side of said ?rst resonant
circuit and the junction of said condensers, a
direct current blocking condenser series-inserted
between sections of said coil, and means for in
will be observed that in this modi?cation of the
invention the control grid 18 of the triode section
of tube 78 is driven from one half the output
reactor 12 of the FM detector circuit.
In this way a single-ended audio output is
secured, instead of a push-pull output as in the
case of Figs. 1, 2 and 3. When the slidable tap
it is at the upper end of resistor ‘l5 there will
be maximum audio signal voltage applied to the
control grid ‘l8. It will be understood that the
functioning of the discriminator-recti?er circuit
is the same as was described in connection with
Figs. 2 and 3. It will, also, be observed that what
is common to each of Figs. 1 to 4 inclusive is
that the opposed diode recti?ers have a common
grounded electron emitter connection, and that
dividually adjusting the inductance magnitudes
in each of said resonant circuits.
Ll. In combination, a primary circuit, means for
supplying angle modulated carrier energy there
to, a secondary circuit resonant to the mean
frequency of said carrier‘ energy and comprising
a coil and a pair of series-connected condensers
arranged in shunt with said coil, said circuits
being inductively coupled with each other. means
conductively connecting an alternating current
each diode section is shunted by a load resistance
potential point on the primary circuit to the junc
element, while modulation output connections
tion of said pair of condensers, a diode recti?er
having its anode connected to one end of said
are made to points on the load elements which
are of like direct current polarity and opposite
audio polarity, and of magnitudes dependent
upon the value of the instantaneous frequency
of the applied FM signals with respect to a pre
determined reference frequency.
While I have indicated and described systems
for carrying my invention into e?fect, it will be
apparent to one skilled in the art that my inven
tion is by no means limited to the particular
organizations shown and described, but that
many modi?cations may be made without de
parting from the scope of my invention.
What I claim is:
1. In a discriminator-recti?er circuit, a ?rst
resonant circuit comprising a coil and a pair of
series-connected condensers arranged in shunt
with the said coil, a second resonant circuit hav
ing a normal frequency equal to the normal fre
quency of the ?rst resonant circuit, means re
coil and to one of said pair of condensers, a second
diode recti?er having its anode connected to the
opposite end of said coil and to the other of
said pair of condensers, a ?rst load resistor con
nected in shunt to one of said recti?ers, a second
load resistor connected in shunt with the second
ecti?er, means for establishing the cathode end
of each one of said load resistors at a common
relatively ?xed potential, a direct current block
ing condenser inserted in series between half
51 sections of said secondary coil, and a push-pull
ampli?er having separate modulation signal volt
age connections to respective points of like direct
current polarity but opposite audio polarity of said
load resistors.
5. In combination, a ?rst resonant circuit com
prising a coil and a pair of series-connected
condensers, a second resonant circuit having a
normal frequency equal to the normal frequency
of the ?rst resonant circuit, means reactively
ductive means connecting one side of said second 75 coupling said two resonant circuits, means con
actively coupling said two resonant circuits, con
2,412,482
11
necting one side of said second circuit to the
junction of said pair of condensers, a ?rst diode
recti?er having its anode connected to one end
of said coil, a second diode recti?er having its
anode connected to the opposite end of said coil,
a condenser interposed between sections of said
0011, a ?rst load resistor connected in shunt to one
of said recti?ers, a second load resistor connected
in shunt with the second recti?er, and means for
.
12
cuit tuned to said predetermined frequency, a
connection between one side of said ?rst resonant
circuit and the junction of said condensers, a
direct current blocking condenser series-inserted
between equal sections of said coil, and means
for individually adjusting the inductance mag
nitudes in each of said resonant circuits.
8. In combination, a primary circuit, means
for supplying angle modulated carrier energy
establishing the cathode ends of both of said load 10 thereto, a secondary circuit resonant to the mean
frequency of said carrier energy and comprising a
resistors at ground potential.
coil and a pair of series-connected condenser
arranged in shunt with said coil, said circuits
being inductively coupled with each other, means
circuit comprising a second coil shunted by a pair 15 conductively connecting an alternating current
potential point on the primary circuit to the
of series-arranged capacitors, the second circuit
junction of said pair of condensers, a diode rec
being tuned to said predetermined frequency, a
ti?ei- having its anode connected to one end of
direct connection from one side of the ?rst tuned
said coil and to one of said pair of condensers,
circuit to the junction of said two capacitors, a
direct current blocking condenser in series circuit 20 a second diode recti?er having its anode con
nected to the opposite end of said coil and to
between two halves or equal sections of said
the other of said pair of condensers, a ?rst load
second coil, a pair of diodes, each diode having
resistor connected in shunt to one of said rec
its anode connected to a respective end of the
ti?ers, a second equal load resistor connected
second coil, separate resistors of equal magni
tude respectively shunting said diodes, means 25 in shunt with the second recti?er, means for es
tablishing the cathode end of each one of said
grounding the cathodes of both diodes, and sep
load resistors at a common relatively ?xed po
arate modulation utilization circuits connected to
tential, a direct current blocking condenser in
the opposite sides of the blocking condenser.
serted in series between the equal half sections
7. In combination, a parallel resonant circuit
tuned to a predetermined signal frequency, a coil 30 of said secondary coil, and a push-pull ampli?er
having separate modulation signal voltage con
magnetically coupled to said parallel resonant
nections to respective points of like polarity of
circuit, a pair of condensers connected in series
said load resistors.
relation across said coil and cooperating with the
BENJAMIN S. VILKOMERSON.
latter to provide a second parallel resonant cir
6. In a frequency discriminator system, a ?rst
circuit comprising a coil and a condenser tuned
to a predetermined signal frequency, a second
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