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Патент USA US2134033

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Oct. 25, 1938.
original Filed June'ö, 1935
2 sheets-sheet
06f. 25, 1938..
Original Filed June 5, 1955
2 Sheets-Sheet 2
yPatented Oct. 25, 1938
Murray G. Crosby, Riverhead,` N. Y., assignor to
vRadio Corporation of America, a corporation
of Delaware "
Application June 5, 1935, Serial No. 25,026
Renewed December 21, 1937
13 claims. (c1. 25o-_20)
This disclosure relates to'a frequency or phase
modulation receiver wherein the received energy
is frequency multiplied and thence converted to
passed through a harmonic generator or frequency
multiplier. In this ‘manner the separate har
monic generator is dispensed with and the change
amplitude modulation by means of a frequency
The resulting
amplitude modulation in the output of the con
version circuit is detected in the usual Way if
from one order of frequency multiplication to an
5. modulation conversion circuit.
frequency modulation is being received. If phase
modulation is being received, equalization may be
applied to correct for the inherent frequency'dis
An object of this invention is to provide a sim
ple receiver for the purpose of detecting and trac
ing extraneous or unwanted' frequency or phase
other isv effected by merely tuning the local oscil
lator. vWhere' a separate frequency multiplier is
used, the- change of> order of multiplication re
quires the tuning ofl several stages.
The novel> features- of my invention yhave been
pointed out with particularity in the claimsv ap- .
pended hereto, as required by law.r The natureof
my invention and the manner in which the same
operates will be understood from the following'de
tailed description thereof Y and therefrom when
plying frequency multiplication plus heterodyning
readk in connection with the attached drawings
through which like- reference characters indicate
to the received energy the depth offrequency or
phase modulation is multiplied by the order of
like parts insofar as possible, and in which:
Figs. l and 2 each illustrate different modifica
the frequency multiplicationy so that the receiver
tions of wave receiving means- arranged in ac-r
modulation on a modulated transmitter. By ap
may be made vultra-sensitive and more suitable cordance with the principles of my invention.
for working with 10W degrees of modulation. This
feature is especially valuable in the case of low
modulation frequency or phase modulation where
the effective degree of frequency modulation.y is
25 low and the frequency modulation converting cir
cuit is insensitive to these modulations.
The present receivers available for detecting
phase modulation are usually considerably com
plicated Whereas frequency modulation receivers
are fairly simple.
Phase modulation. may be re
` ceîved on a frequency modulation receiver, but
lation and the modulations are converted in a
novel circuit into modulationsA of a different charf- 25
In Fig. 2, the depth of modulation is increased
by» harmonic action of the heterodyne demodu
latory and the resulting energy is converted and
Figs. 3. and 4 are characteristic curves, illus
the inherent difference between frequency and
phase modulation makes the output of a fre
trating the operation of the demodulatorp and
harmonic generating tube in the circuit of Fig. 2;l
quency modulation receiver, receiving phase
modulation, directly proportional to frequency.
Consequently, the receiver would be insensitive
to the low modulation frequencies of phase modu
lation. Equalizing circuits may be applied to the
detected energy of this type of a receiver to cor
40 rect for the frequency distortion. However, in
cases where unwanted modulations are
traced, equalization is unnecessary. The receiver
of this invention then proves valuable.
An advantage of the principles disclosed in this
45 invention is that by using this frequency multi
-Figs. 5, 6 and '7 are graphs illustratingthe op-l 35.
eration of the demodulating means in the circuit.
'I'he circuit of Fig. 1 shows _one form of the
receiver wherein a separate frequency multiplier
is used. The signal from antenna I is amplified 4.0
in radio frequency amplifier 2 and heterodyned to
intermediate frequency by means of detector 3
and high frequency oscillator 4; Intermediate
frequency amplifier 5 ampli?les and-filters the .
ments of the frequency modulation converting
circuits do not have to be so exacting and receiver
design is facilitated. Thus a frequency multipli
intermediate frequency energy. The intermedi 45
ate frequency energy is then passed through the
frequency multiplier 6 Where it is multiplied the
desired number of times.. By means of detector 'l
and intermediate frequency oscillator 8, the mul
cation of two might be employed `in order to re
duce the lengthof the artificial line or retard cir
tiplied energy is heterodyned to a lower frequency 50
which is more suitable for filtering in the fre
cuit in the artiñcial line type converting circuit,
quency modulation demodulator coupled tol Hl.
This demodulator may be any type of frequency
modulation converting circuit-that is, a circuit
plication plus heterodyning system, the require
to one half.
A further novel feature of this invention is one
of its means for producing frequency multiplica
tion. By utilizing the higher order effects of a
power law detector, a harmonic of the signal is
caused to heterodyne with a harmonic of the local
oscillator so that the resulting output is the same
In Fig. '1, the intermediate frequency energy
resulting from the heterodyne detectory is fre
quency multiplied to increase the depth of modu
as though the intermediate frequency energy were
capable of translating frequency modulated en 55
ergy to its signal energy. vFor example, the output
of the intermediate frequency amplifier may be
fed tothe primary Winding of transformer Ill, the
secondary winding of which is coupled to control
electrodes in tubes- l2 and I4', as shown. The
output of tube I2 is filtered by ñlter sections I5 Vparallel connection of transformer 9 is used. A
and I6 and the filtered energy is then` fed to the similar converting and demodulating system has
control grid of a detector tubefll and also to been described in detail and claimed in my U. S.
the control grid of a combining tube I3. The application Ser. No. 703,770, filed Dec. 23, 1933,
output of tube I4 is combined with the output` . Patent No. 2,061,611, November 10, 1936.
of tube I3, through the impedance coupling 22. 'f Thus, it is seen that the signal is received on
A potentiometer 23 controls the volume of .thej a superheterodyne receiver, units I, 2, 3, 4 and 5
energy supplied from the ~-filters I5, .I6 Vto _theY and is frequency multiplied to a higher frequency
tube I3. Potentiometer 2I`regulates the voltage Ä so thatV the depth of its phase or frequency modu
10 supplied from the impedance coupling 22 to theV lation is multiplied. This'higher depth modula
control grid of detector tube I8, so that this tion is then 'heterodyned down to a lower fre
energy is equal to the energy >that-'isv fed from , quency which is more suitable for receiving on
I5, I6 to the control grid of detector tube> I1.
.either directly from the‘secondary winding of
I9f^or by way of a filter circuit, depending upon
the positiorrof switch 26. Y Switch 24‘regulates the
¢=fd/fm, where fd=frequency deviation and
15 the detectors I‘I, I8.
The combined signal ap
pears 'iin an 'indicating or> recording' device 20
phase vof 'combination 'of- the audio outputs of
the two detectors. When frequency modulated
waves are received, the outputs of 'tubes I'I and
I8 are connected in push-pull relation. By re
versing switch 24 to connect >the outputs of tubes
I 1 ’and I8 in paralleL'amplitude modulated waves
may be received.
VThe >principle ofthe operation of a back-to
back type of frequency modulation receiverV re
a filter-type'frequency modulation receiver. The
first intermediate frequency voltage is given by:
çE sin (wt-4: cos pt)
where w=2arr intermediate frequency, f.¢=phase
Transformer I9 combines the audio outputs of
deviation in the case ofV phasel modulation or
fm'=modulaiton frequency, in the case of fre
quency’modulation p=21rím~ Hence the equa
tion covers both phase and frequency modulation,
Ydependingupon whether ¢> indicates phase devia
tion or modulation index, fri/fm.` In this respect,
Vthe following analysis is general-that is, it covers
both the frequency modulation and phase mod-`
ulation. cases.
-Y It is known to the art that after passing the
quires that one *detector »be fed by thesignal . intermediate frequency voltage through the fre
passed through a filterof positive slope, as shown quency multiplier, the> result is:
in Fig.f5, andthe other detector by a filter of
e=E sin N(wt„n-¢ cos pt)
negative slope, asshownin Fig. 6. Ordinarily,
two filters having these slopes are built separately.
However, by combining a filter of one slope lwith where N is Vthe order of frequency multiplication.
a filter of -flat »topïcharacteristic as -shown by’ VIt is seen from (2) and (3), that f as Well as ¢ $5
Fig. 7 , a filter-'of opposite slope may be obtained.
are multiplied by N; consequently, the frequency
For instance, the output of the filterk of Fig. 6 y as Well >as the depth ofV modulation are both
may be subtracted from‘the output of ‘ the'filter multiplied.
of Fig. 7 andrthe'resultant wouldfbera negative
40 slope filter, as'shown by Fig. 5. Inthis manner,
the output of the filter I5, I6 in Fig. 1 may be
given by Fig. 6, for ,fc as the carrier frequency
and fo >fZ,/the band limits. The output of tube
I4 is an aperiodic amplification of the signal giv
45 ing a fiat top characteristic, like that of Fig. 7,
although not necessarily a bandpass action, as
Fig. 7iportrays. (In Figs. v5, Gland 7, the char
This multiplied energy is then heterodyned
fromV its -frequency vNî to a third intermediate 40
frequency which is suitable for filtering; the re
sult is:>
, l
ve=E sin (21rf1t-N¢ cos pt)
Equation (4)V Vshows ‘that the energy has been 45
converted >from a frequency Í of (l) with a
depth of modulation of ¢ to a frequency f1 with
a .depthof modulation of Nc. Consequently, the
filterscut 'off at the outer limits lof the received depth of modulation of all the modulating fre
50 wave bandi iii-the actual Ycase this would only be quencies has been increased. As a result, the 50
acteristics are assumed to be ideal, so that the
approximated.) ' The combination of the outputs
sensitivity of the receiver has been increased
of ytubes I3 and I4 _is in reality a subtraction‘of
sufficiently so 'that a frequency modulation con
the characteristics“ of Fig; 6î` from that of Fig; 7,
verting circuit may beused for the reception of
so that Fig. 5 is obtained, thus', the slope of the
filter has been reversed. Thus, feeding the out
put of the filter I5, I 6 directly to one detector
tube, say I'I, and reversing the slope for the other
detector, say I8, gives the equivalents of two fil
ters and a back-to-back action. Tubes I3 and I4
phasermodulation, especially on the lower mod
ulation frequencies of phase modulation. The 55
fact that the output’of a frequency modulation
60 then merely _function to apply the output of the
one filter with its slope reversedto thedetector
I8. The inputs to the two detectors are bal
anced by means of the potentiometer 2 l .
For the reception of phase or frequency modu
receiver, which receiving phase modulation, is
directly proportional to frequency may best be
pointed out by differentiating the phase of (4)
toobtain the instantaneous frequency of the 60
lation, the use of opposite slope demodulating '
ñlter effects applied from I5, IIîtoV I'I and from
_22 to I 8 causes the resulting two amplitudeamodu
lations fed V_from the outputs of detectors I1 and
IB to be 180° out of phase. To make the de
tected outputs add, they are combined in the
transformer I9 with the series of push-pull con
nectionsv to produce an 180° reversal of phase of
Consequently, if (7) is linear and faithful to the
signal of modulation on a frequency modulation
receiver, ,a wave with an instantaneous frequency
one output.
given by (6) would produce an output propor
tional- to fm, the modulation frequency. For this
tion, however, the phaseofthe .modulation is
unaffected bythe demodulating filters and the
In the case of amplitude modula
reason, the principle of frequency multiplication 75
at the receiver becomes'valuable for the lower
vmodulation rfrequencies of phase modulation.>
tionen-efficients a1 and> ai are made large com
pared to b1 b2, c1 cz, etc.,'by adjusting the grid
The circuit of Fig. 2 is an adaptation ofthe
biases so that the signal and oscillator -swing over
higher order effect type of detector and frequency
the linear portion of the tube characteristics as
the point “a” in’ Figs. lSand 4.
multiplier, and a long line type of frequency
modulation converting circuit. The 'radio' fre
quency amplifier 2 fed by antenna I feeds the
control grid Gl of the pentode detector ’3. The
suppressor grid G2 of tube 3 is fed by energy
10 from the high frequency oscillator 4'. ‘The oscil
lator 4 may be tuned so that fundamental en
ergy therefrom beats'with the harmonic of the
Terms (5) ,A (9) , etc., are Vthe higher order terms
which produce the frequency multiplication.
Term (5) isthe product of the squares of the
signal and local oscillator which produces 'the
beat between the second harmonic of the signal
and the second harmonic of the ocillator. In the
same manner term (8) produces the »beats be
signal carrying wave energy or may be tuned‘so
that -a harmonic of the fundamental wave of the
-15 oscillator beatsv with a harmonic of the funda
mental signal carrying Wave energy. The fre
tween the third harmonics.' The remaining terms
quency multiplied and heterodyned output of
detector 3 is fed tothe intermediate frequency
operate the detectorïas ar frequency multiplying
detector, coefficients b1, b2, c1 c2, etc., must be
amplifier 5 where it is amplified and filtered. The
output of 5 is fed to the grids of detectors 28 and
29 via transformer 21 which has an astatic
shield 35. It is also fed via line'l 2B to the detector
grids through the midtap of 21. The output of
detectors 28 and 29 is resistance coupled to audio
25 amplifiers 30 and 3| and translated by pho-nes 23.
Thel frequency modulation conversion `circuit
from 5 on is essentially'the same as Fig. 3 of my
U. S. Appln; Ser. No. 618,154, filed June- 20, 1932.
In the Fig. l2 circuit, the signal energy is fed
r30 to the control grid of the pentode detector, and
the high frequency oscillator energy to the sup
pressor grid. By adjusting these two gridsl so
that they operate on the non-linear portion of
their dynamic characteristics, a harmonic of the
35 signal may be heterodyned by a harmonic of the
local oscillator to produce anV intermediate fre
quency. The resultant effect is then the same
as though the signal had been frequency mul
tiplied by means of a separate-frequency mul
tiplier, and heterodynedfto the intermediate fre
quency by means of an 'intermediate frequency
oscillator. The manner in which the pentode
detector acts to produce this type of frequency
(2), (3), (4) , (8), etc., all contribute fundamental
and harmonic beats but to a lesser degree than r15
(l), (5), (9), etc. Thus, it can be seen that, to
made as large as possible. This is done by oper
ating with the grid biases at the curved portion 20
of the characteristics as at "b” of Figs. 3 and_4.
Also the output is an exponential function of the
two input voltages so that the input'voltages
must be made highY comparedl to their normal
detection values; that is, the'detector should be 25
In Vorder to show how term (5) f produces a beat ,
between the second harmonic of the signal and
the second harmonic of the oscillator, the signal
of equation ( 1) will be Vapplied as e1 of one grid 30
anda local oscillator
, , 62:11"or sin' ,wir
on the other grid.
Term. <5) of 101s;
j: [J1/52E? sin2 (Wt-<3 Vcos PÜEUZ sinz wlt
(àl-à cos 2Wt)
Multiplying and separating out the heterodyne 40
multiplying is'most easily explained by the fol
lowing mathematical-analysis:
The curves of Figs. 3 and 4 show the platev
current-control grid Vvoltage (Ip=E'g1) and plate
cos((2wt- 2W1t)-2¢ cos pt) ` (16)
acteristics fo-r a pentode detector'. `It is well Equation (16) gives the beats between the second
known that the varying current in the output Y harmonic of the signal, (/) and the oscillator,
(//)'. The depth of phase or frequency modu
of the detector, due to a single grid, may be ex
current suppressor grid voltage (Ip=Eg2) char
pressed asl a function of the'sinusoidal voltage
impressed upon the input by the power series:
The output due to two grids will be given by:
lation is 2(1). Consequently, the intermediate fre
quency signal is
Multiplying (9) out and eliminating all but the
» (3)
]=[ a1a2e1e2 l” blaeeizez “i” ciazeíßez "l"
+ älbzelezz + b1b2e12ß22 + 01132613622 +
+ "1116261623 + b162912623 “l” 0102613823 + +100)
From (10) it can be seen thatterm ( 1) will pro
weI. 1?.:KE2E02> cos (unt-241 cos- pft)
Of course, if the Nth order of frequency multi
plication were used, the 2c would `be replaced
by Ngs.
60 terms causing beats or a heterodyneoutputz~
After the radioY frequency energy has been
heterodyned by` the> frequency multiplying detec
tor, it is amplified at intermediate frequency and V60
passed to the artificial line type of frequency
modulation circuit.
In describing thev manner in which the fre
quency modulated waves of increased modulation
depth inthe output of 5 are democlulated,l it 65
must be kept in mind that conversion of the fre
quency modulations depends upon the fact that
the electrical length of agñlter or transmission
line, such as 26, which consists of a series of sec
duce beats between the fundamental of the sig
tions composed of inductive, capacitive and/or 70
nal applied on one grid, say GI, and the funda
resistive elements in a series'and/or .parallel
mental of the local oscillator applied to the other
grid, say G2. When the detector isA adjusted for
normal detection, Without frequency multiplica
saidelements in said arrangement, varies with
arrangements or any one of a combination of
the impressed'frequency.' In the following ex.
tween »Zw and `w1 instead of 2w and 2wi. Since
the amplitude is proportional to az b1 instead of
bi-bz and E0 instead. of`Eo2, the efficiency of this
type of multiplication, where the oscillator is
tuned Vto the harmonic, is greater than that where
a harmonic of the oscillator beats with a har
planation, a transmission line, such 'as 26,"will be
utilized, although it Will be understood that a file
ter, such as a high pass„low pass, bandpass, band
elimination, etc., may be used.' `If the line is
a given number of wave lengths long-forI a pre
determined frequency, at a higher.. frequency4 the
electrical length will be greater and-at aÀ lower
frequency the velectricalv length of the line will b_e
' monic of the signal.
output of the line changeY with respect to that at
superheterodyne receiver might be used. That is,
the input ofthe line,` if the frequency of the
signal transmitted by the line is varied. Conse
quently, if the signal impressed on the input _of
the line iscombined with the signal‘at the out
the radio- frequency amplifier 2 of Fig. 2 could
ing and heterodyning could- be done at any fre -15
put of the line„an~ adjustment of the line may be
made, sothatthephase difference atA the voltage
The principle of multiplying the . received
energy can be applied‘to the use of any type of
be the intermediate frequency amplifier of a
superheterodyne receiver.
of the signal impressed _on the input of the line
and the voltage of the signal appearing on the
output of the lineV increases Vas the degree; of
Vfrequency modulation is increased. Thisphase
difference will cause a variation in_the amplitude
of the resultant of the combined voltages, so
that an amplitude` modulation is formed which
is truly characteristic of the frequency modu
lation of the original signal. ,
A triode detector maybe used in place of the
-pentode detector to produce the multiplying and
heterodyning‘action. The higher order effects
producer the same sort of harmonic beats in any
type of detector.
It ' is understoody that limiting or automatic
volume control may be incorporated at any point
in these receivers in order that signal variations
may be minimized. Similarly, automatic fre
quency or tuning control may be applied to main- f
’tain the receiver in tune with the signal.
and 29 are simultaneously> energized cophasally
~ What is claimed is:
by energy derived from a selected point on the re
tard circuit26.` By -properly selecting the tap onY
26 the resulting amplitude modulations due to
the combination of the energy from the two paths
which is fed to the' control grids ofA detectors 28V
and 29 may be made 180° out of phase. The
resultants of the -phase displaced energies from
40 the two paths on the control grids of 28 and`29
produce variationsv in the amplitude ofthe energy
>in the output of tubes 28 and 29 which are char
acteristic of the frequency modulations on the
signal wave. The energy from the outputs of
tubes 28 and 29 is supplied by way of couplings
40 and 4I to coupling tubes 30 and 3| and from
the output of the coupling tubes 30 and 3| to in
grid-like electrodes, a circuit coupling another
of said grid-like electrodes to a source of signal
modulated wave' energy, and means for biasing
the grid-like` electrodes in said tube negative
relative to the potential of the cathode of said
tube an amount such-that the said tube operates
2. Signal modulated wave energy demodulat
ing means as recited in claim 1 including
means for tuning said source of oscillatory en
ergyto a frequency of -the order of the har
If frequency modulated waves are
of tubes 30 'and 3| are connected in parallel.
1. In asignal modulated wave energy demod
ulating means, 'a thermionic tube having a plu
rality of grid-likeelectrodes and a cathode, a 35
source of oscillatory energy coupled to one of said
to beat a harmonic of the. wave energy with en
ergy from said source of oscillatory energy.
monic frequency of the modulated wave energy.
to be received, the outputs of tubes 30 and 3l are
5.0 connected in push-pull relation. If amplitude
modulated waves are to bev received, the outputs
3.V In a frequency deviation multiplier. a ther'- »
mionic tube having a> plurality of gridflike elec
trodes a cathode and an anode, a source of os
Another method of utilizing the higherorder
effect detector for this type of frequency multi
plication and detection would be to tune the
local oscillator to approximately the harmonic
cillatory energy coupled to one of said grid-like
electrodes, a circuit coupling another of said
grid-like electrodes to a source of signal modu 55
of the signal so that a heterodyne, between the
grid-like electrodes in said tube to negative po
tentials relative to the cathode potential such
that the said tube operates to beat a harmonic
of the signal modulated wave energy with a har 60
monic of the fundamental oscillatory energy
fundamental of the local oscillator and a ;har~
monic of the signal, is obtained.V This Vtype of
operation utilizes terms (2), (4),> (3), (6), etc.
of Equation r(10)'. YWith e1 as the signal and ez
'as the local oscillator, terms (2), (3) , etc., would
be utilized.
With e1 as the oscillator and e2 as
the signal, terms (4), (7), etc., would be utilized.
65 As an example with e1 as the'signaland e2 as the
frequency or phase modulation conversion circuit
in phase opposition from unretarded energy de
rived‘from the output of rtheintermediate fre
quency amplifier 5. The control grids of tubes 28
dicator 20.
Thus, the multiply
for use on either phase or frequency modulation. 120
In the specific application,'the control grids of
the differential detectors 28 and «29 are energized
heterodyningat the first detector as shown in
Fig. 2, the second detector ofl a triple detection 10
The fact that Vthis electricalA lengthdoes
10 change with frequency makes the phase at the
I 15
Instead >of performing the multiplying and
lated wave energy, and means for biasing the
from said source.
4. Phase or frequency modulated wave energy
signalling means comprising, means for increas
ing the frequency of said wave energy for in
creasing the depth of phase or frequency modu
local oscillator tuned to approximately twice the
frequency ofthe signal, the development similar
to that of Equations (11) tov (17) `gives the fol
lation on said wave energy, modulated wave en
lowing heterodyne output:
sloping characteristic coupling said first named
]=a2b1e12e; (term (2) of Erq. (10))
Equation (19) is the same asr (16) except for
47.5 its amplitude and the fact that the beats are be
ergy demodulating means, a circuit having a
means to said modulated wave energy demodu 70
lating means, and a secondcircuit having a char
acteristic which slopes in a sense opposite to the
sloping characteristic of said first circuit cou
pling said first named means to said demodulat
ing means.
5. PhaseV :or „frequency _modulated Vvvaye `.energy
signalling means comprising, means for 'increas
ing .the frequency of said 'vv-ave nenergy, thereby
increasing the depth of modulation .on said Wave
energy, modulated -vvave energy demodulating
means, .a circuitincluding a filter having a slop
ing `cha-rac-teristic coupling >s_a-id,_»demodi-_ilrating
means to 4said first nar-ned means, ¿a _circuit>` in
cluding a filter having .a flat topped charac-ter
named means, ,al circpit
LO istic coupled to said
includingv said :filter ‘having a sloping character
istic coupled to said first named means, combin
ing means coupled with the output of said last
two circuits, and a coupling between said com
tubaand 4an 4~indicator V`coupled `with ¿both of said
filters. ,ì
9. Ina frequency ,or ¿phase modulated Wave en
ergy'demodulatingpsystem, wav-e absorbingmeans,
an ampliñerçeupled there@ ther-mimic. will@
having a plurality of grid-like electrodesa >.catli
ode, _and v_an anode, .a sourceof local voscillations
coupled to .one of said grid-like,electrodeslacir
cuit ¿coupling another of ,sa-id grid-like -auxiliary
electrodes to Ithe koutput ,of said amplifier,¿means 10
for biasingwthe grid-like .electrodes in said tube
relative to the cathode to such potentials'that
said tube operates as a harmonic generator, an
bining means and said demodulating means.
6. Phase or frequency modulated wave energy
signalling means comprising, means for increas
ing the frequency of said wave energy for in--
intermediate frequency amplifier having an input
coupled to the anode of said tube, said intermedi 15
ate frequency amplifier having an output, a cir
cuit of considerable electrical reactance coupled to
the output of said intermediate frequency ampli
creasing the depth of phase or frequency modula
fier, a pair of detector tubes each having a con
20 tion on said Wave energy, modulated Wave energy
demodulating means, a circuit having a sloping
characteristic coupling said first named means
to said demodulating means, a second circuit hav
ing a characteristic which slopes in a sense op
25 posite to the sloping characteristic of said first
circuit coupling said first means to said demodu
lating means, and means connected with said de
modulating means for combining the outputs of
said circuits in phase or in phase opposition.
‘7. Signal modulated Wave energy signalling
means comprising, modulated wave absorbing and
amplifying means, a demodulator and a source
of local oscillations coupled to said amplifying
means, said demodulator having an output, a
35 frequency multiplier coupled to the output of said
demodulator, a source of _local oscillations and a
trol grid, a circuit coupling the control grids'of 20
said detector tubes in phase opposition to the out
put of said intermediate frequency amplifier, and
a circuit connecting the control grids of said
detector tubes cophasally to said circuit of con
siderable electrical reactance.
10. In a frequency or phase modulated Wave
energy demodulating system, Wave energy ab
sorbing means, an amplifier coupled thereto, a
thermionic tube having a plurality of grid-like
electrodes, a cathode, and an'anode, a source of 30
local oscillations coupled to one of said grid-like
electrodes, a circuit coupling another of said grid
like electrodes to the output of said amplifier,
means for biasing the grid-like electrodes in said
tube relative to the cathode to such potentials 35
that said tube operates as a harmonic generator,
demodulator coupled to said frequency multiplier,
an intermediate frequency amplifier having an `
said demodulator having an output, an inter
mediate frequency amplifier having an output,
input coupled to the anode of said tube, said in
termediate frequency amplifier having an output,
a transmission line coupled to the output of said
intermediate frequency amplifier, a pair of de
a pair of thermionic tubes each having a control
tector tubes each having a control grid and an
mediate frequency amplifier coupled to the out
40 put of said last named demodulator, said inter
grid and having their control grids connected in
parallel and coupled to the output of said inter
45 mediate frequency amplifier, each of said tubes
output electrode, a circuit coupling the control
grids in said detector tubes in phase opposition to
the output of said intermediate frequency am
plifier, a circuit connecting the control grids of 45
thermionic tube having a control grid coupled
to the output of one of said last named tubes, said
additional tube also having an output electrode,
an indicator, and means for coupling the output
electrodes of said three tubes to said indicator.
said detector tubes to a point on said transmis
also having an output electrode, an additional
8. In a frequency or phase modulated wave en
ergy signalling system, Wave absorbing and am
plifying means, a demodulator and a source of
55 local oscillations coupled to said amplifying
means, said demodulator having an output, a fre
quency multiplier coupled to the output of said
demodulator, a source of local oscillations and a
demodulator coupled to said frequency multiplier,
60 said demodulator havingan output,an intermedi
ate frequency amplifier coupled to the output of
said last named demodulator, said intermediate
frequency amplifier' having an output, a pair of
thermionic tubes each having a control grid con
sion line, and an indicator coupled with the out
put electrodes of said detector tubes.
l1. In a system for demodulating Wave energy
the frequency of which has been modulated in 50
accordance with signals, means for multiplying
the frequency of said wave energy to thereby
multiply the degree or amount of frequency mod
ulation of said wave energy, means comprising a
plurality of paths for said wave energy, said paths 55
being capable of passing all the frequencies of the
Wave energy to be demodulated, means connected
with said first named means for impressing Wave
energy representative of said Wave energy of mul
tiplied frequency and multiplied degree or amount 60
of frequency modulation on said paths, reactive `
elements in one of said paths, means for combin
ing the waves passed by one of said paths With
that passed by the other of said paths, and means
65 nected to the output of said intermediate fre
for producing indications of the combined Waves. 65
quency amplifier, each of said tubes alsov having
an output electrode, an additional thermionic
tube having a control grid coupled by way of
filters of sloping characteristic to the output elec
trode of one of said pair of tubes, said additional
tube having an output electrode, a filter having a
square topped characteristic coupled With the
output electrode of the other of said pair of tubes
75 and with the output electrode of said additional
12. The method of receiving a frequency modu
lated Wave which consists in multiplying the fre
quency of said frequency modulated Wave to
thereby increase its frequency and the degree of
frequency modulation of the wave of increased
frequency, deriving fromsaid Wave of increased
frequency and increased degree of modulation a
plurality of currents each varying in frequency in
accordance with variationsof the Wave of mul 75
tiplied frequency, passing the currents-’of Vall vof
said frequencies through two paths having differ
ent characteristics of transmission for said cur
rents and combining the output currents of these
Ul two> paths in a detector to re-create the trans
mitted signals.
13.- The method of receiving a frequency modu
said wave energy of multiplied frequency a. plu
'rality of currents,v each varying in frequency in
accordance with variations in said energy of mul
tiplied frequency, passing each of the derived cur
rents through a path, causing one of said paths
to change the phase of the current passing there
through with respect to that of the current passed
vloy another path and combining the output cur-l
lated wave which includes the steps of multiply
ing >the frequency of said frequency modulated Y rents of these two last mentioned paths in a de
Wave to thereby'increase the degree of frequency tector to re-create the transmitted signal.
modulation of the resultant energy,v deriving from
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