`June 3,l 1.947»
l... E. THOMPSON
2,421,727À
MULTIPLEX SYSTEM HAVING CHANNELS ADDED AT A RELAY STATION
Filed April 9, 1945.
2 Sheets-Sheet l
‘
INVENTOR.
'
LELAND E. THOMPSON
BY. )fé
o
`
MM
ATTORNEY
June 3, 1947-
Y l.. E. THOMPSON
2,421,727 _
MULTIPLEX SYSTEM HAVING CHANNELS ADDED AT À RELAY STATlON
_Filed April `9, 1945
2 sheets-_smet 2
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LELAND E. THOMPSON
BY
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~ _ MWL,
ATTORNEY
Patented June 3, 1947
2,421,727
,UNITED STATES PATENT „OFFICE
MULTIPLEX SYSTEM HAVING CHANNELS
ADDED AT A RELAY STATION
'
Leland E. Thompson, Merchantvìlle, N. J., as
signor to Radio Corporation of America, a cor
poration of Delaware
Application April 9, 1945, Serial N0. `587,250 ,
20 Claims.
1
-My present invention relates to a multi-chan
‘nel <radiorelaying system such as described in
my co-pending application Serial Number 576,453,
filed February 6, 1945.
' As described in my co-pending application, ‘sev
eral different signaling channels are used to in
dependently amplitude modulate separate, rela
"tively lów frequency, sub-sub carriers. The lower
side bands of the modulated sub-sub carriers are
filtered out, amplified, combined and used to an
gle, or more specifically, frequency modulate a
>common sub-carrier wave having a mean fre~
(Cl. 179415) i
l
2
a second frequency lclemodulation process so’as
to reproduce the combined single side band chan
nels originally transmitted. The new channel or
intelligence band may then be combined with the
output of the second demodulator and the paral
leled channels may be `used to frequency `modulate
a newly generated, common sub-carrier andthe
latter may be employed to frequency modulate a
newly `generated radio frequency carrier. This
method isobjectionable, for unless elaborate and
costly equipment in used to increase linearity of
the second frequency demodulator and immedi
quency‘rof, for example, one megacycle. By way
of example, also, six different channels may be
used to produce a maximum frequency swing of
pecially in the event that the process is repeated
approximately plus and minus 200 kilocycles in
the common, frequency modulated sub-carrier.
at a number of repeater or relaying stations.
_
Y It is, therefore, an `object of my present inven
The frequency modulated sub-carrier, having a
tion to provide an improved method and improved
arrangement of instrumentalities for adding one
mean frequency of one megacycle and a maxi»
ately following ‘ modulators, an undesirable
amount of cross modulation will be introduced, es
mum frequency swing of plus and minus 200 kiloe 20 or more intelligence channels to a “through” wave
cycles, is used to frequency or angle modulate the
at a high frequency relay or repeater station
radiated carrier.
The latter may have a mean
frequency of, for example, 3000 megacycles. The
without introducing »objectionable distortion or
cross modulation.
`
`
3000 megacycle radiated carrier may be swung
A further object of my present invention is to
or frequency modulated a maximum amount of, 25 `provide simplified equipment at relaying points
for example, plus and minus one megacycle by
Aenabling the addition of one or more channels to
the frequency modulated sub-carrier.
“‘through”- waves already carrying one or more
The 3000 megacycle carrier is directively radi
intelligence frequency bands.
ated to a distant relaying point for retransmis
' `In accordance with one form of my present
sion to a receiving terminal or to still another
invention wherein one or more intelligence bands
relaying point. The frequency of retransmission
or signals are added at a high frequency relaying
takes place at a frequency differentl than that
station, such as described in my co-pending ap
received such as, fur example, 3010 megacycles.
plicationSerial Number 576,453,‘iiled February
To effect this frequency transformation at a
Y6, 1945, a multiply modulated wave is subjected,
relaying point or station, the received high fre
at the 'relaying station, to a single demodulation.
quency carrier having an unmodulated frequency
Waves derived from the demodulation are then
of, say, 3000 megacycles, is heterodyned down to
heterodyned with an oscillation which has been
some convenient intermediate frequency such as
-modulated with one or more signals which are to
30 megacycles. The latter is amplified, limited
be added at the relaying point. Waves derived
and subjected to a frequency demodulation, i. e., 40 from the heterodyning process are then employed
to discriminator-detector action, in order to re
to modulate a locally generated high frequency
produce the common frequency modulated sub
carrier which is to be transmitted on to the ‘next
point in the system.
y
carrier.l This frequency modulated sub-carrier
is further limited and ampliñed and then used
`My present invention will be described more
to frequency modulate a new, `locally generated, 45 speciñcally with‘the` aid of the accompanying
carrier having a frequency of, for example, 3010
drawing wherein Fig. 1 illustrates a radio re
megacycles. The new carrier is directively radi
laying station for relaying a doubly frequency
ated on to the next point in the relay system.
modulated wave and wherein one or more‘sig
In such a multi-channel radio relay system, it
haling channels may be added at the relaying
is desirable, in some cases, to tap in at a relay 50 station with a minimum of distortion and cross
station in order to add one or more signaling
talk, and Fig. 2 is a block diagram of a modi
channels for transmittal, along with the channels
fied form of a relaying station such as shown in
Fig. 1.
‘
‘
valready present, on to the next point in the sys
tem. One way of accomplishing this is to subject
Fig. 1 is a radio relaying station especially
the common frequency modulated sub-carrier to 55 adapted for relaying a multi-channel doubly fre
2,421,727
3
4
quency modulated Wave such as emitted by the
transmitting station of Fig. 1 of my co-pending
ment üll through lines B2, 63 and 65. This chan
neling equipment may correspond, for example,
to the channeling equipment associated with
application Serial Number 576,453, filed February
channels B, C and D of Fig, l of my co-pending
application, provided these channels are not used
on the incoming sub-carrier in line I4. In other
6, 1945. It differs over the relaying system shown
in Fig. 2 of that application in that Fig. 1 herein
describes an arrangement in which one or more
Words, the -inputin 62, t3 and t5 separately mod
signaling channels may be added at the relaying
point with a minimum óf cross modulation and
ulate local oscillators such as IDB, EDC, ’and IOD
of Fig. l of my co-pending application operating
distortion.
`at diiîerent frequencies.
As shown in Fig. 1 herein a Wave such as trans
plication or as transmitted ¿by the -transmitt‘ing
antenna of any one of the relaying stations Vof
my co-pending applicatiomçis received upon <an
and fed into line 58 of Fig. l herein. Obviously,
of course, one‘of the-channels such as 62 of Fig. 1
maybe «fed through-'directly to the reactance tube
«modulator Eä as was done in channel A of Fig. 1
of my co-.pending application, providing this
channel ‘is not 4already in use on the incoming
tenna 2 provided with a parabolic reiiecto'r‘dv in " ’
order to enhance directive reception.
Side bands of the re
sulting modulation are ñltered olf by filters such
¿as fIfdB, IÃCl and IIID of said Fig. 1 and combined
mitted by the transmitter of my co-pending ap
The re
ceived waves, which may have a mean frequency
of 3000 megacycles, are fed 4through line `6 to
sub-'carrier in line I4.
_
apparatus 8 which may include a local `'oscillating
As a result, the output of oscillator ~50 is fre
a first detector, an intermediate frequency ampli 20
quency- modulatedV _by «the output of the channel
equipment. Bü and the frequency modulated Wave
fiery and a, limiter. Apparatus >8„corresponds to
converter- 20'2», beatingpsoillator 204 and inter
mediate frequencyfampliñer 20S of vmy -o_o-pend
ing- ,applicatiom The heterodyned outputof ap
which «appears in line '52 is combined with. the
frequency modulated Wave appearing in -îline ‘3'4
paratus 8 may be, for exam-ple, an intermediate 25 in the Amixer or detector .36. Of ~theresulting
waveslilter 3’8 maybe designed so as -topass- the
frequency-_wave having a mean frequency of 30
dilïe'rence frequency and,. assuming a maximum
mcgacycles anda deviation of plus and >minus one
frequency deviation of v5() kilocycles imparted v-to
oscillator 5t by the signals in line Í58,'the-o1`1tpu-I‘»
y Thiswave- output is fed V’through line luto a
of 3B, Which'may, of course, 'includeva vacuum
first frequency demodulator or discriminator-de
megacycle.
_
v
y
tube limiter if desired, will be a wave Ãhavinga
mean frequency of one megacycle and .a maui
rnum’fr'equency Vswing or frequency modulation
tector I2 correspondingto 2GB of Fig. _2 of my
cci-pending application». 'I‘he outputio'f apparatus
lf2` maybe a wave having a mean frequency of
one `megacycle andjfrequencyrmodulated or swung
of 'plus and 'minus-'250 kilocycles. The-latter will
plus and> minus ¿,200çkilocycles by the 'signaling
truly'represent 'all of the signaling vchannels ap
channels ¿when allfof them areinstantaneously
pearing'inïline lll'and also the additional chan
lnels injected by 1ine'58 carrying signal channels
Qfsuchphase as, toA produce additive» frequency
modulations in_'the common one megacycle sub
Garrìeraprea?ngin li‘rle M- ,
,
on bands derived from channeling equipment 6D.
_ The output _of'ñltér ia’nd'limiter ’38 isfthen fed
,
_Fart Ao_i” the output of the first demodulator I2
appearingin line'lll islfed through line I6 4to a
second demodulatorjZp -and »then to channeling
40
ing 'in "design 'and construction tofther 'frequency
modulated oscillator >21| lof’Fig,` 2 of my coèpend
ing application. Transmitter 4'2, may thus,„for
equipment or ñlters 22'for reproducing one or
more ofthe >original signaling _ currents. The
seconddeinodulator 2û\__c'o_rresponds,to the second
through line #l0 to atransmi‘tterßî.’ correspond
example, be operated at a -mean 4frequency »of
45
3_01'0 megacycles'and the input fed throughline
'4t adjusted `s"o as' to- 'produce la maximum .devia
tion of plus and minus one megacycle inV the wave
discriminatorfdetector 312 «of Fig. 3 of my lco
pending application and the channeling equip
ment 22 correspondsto and includes one ormore
radiated by radiating-antenna'dß. The construc
_of____the filters '5t-_Eiland their „corresponding
converters, 663-14, oscillators SIe-'I5 and filters
l@ tor-_84 _of fg, 3 of _my co-penoling`> application.
' tion of re-radiating lantenna ¿I8 and its «reflector
Another Aportion Ottheoutput of the first de
rn'odulator _I2 _is fed throughlines I 4> and I8 to
a balanced mixer or detector 2-8. Waves derived
50
E16 together "with connecting transmission vline
lili `may beidèntical to that shown in Fig. -1`0fof
my c'o-pending "application
If desiredof'course, switch 54 maybe opened
and channeling equipment 'I2 'corresponding to
_from_a__lo_'cal¿os_cillator 2_S operating-at, for exam 55 channeling equipment ‘611- Amay be Vused ’to-fre
quency modulate ` the nrst ’ beating -*oscillator ~ 26..
ple,¿_ I I__megacycl'es are _alsoufedithrough line y2'I
In that 'event switch 66 would be closed, `a.suitto thebalancedmgixer 28. The sum frequency
ablenlunbler'of'inputs would be provided atÍïM
outputofinixer _28_ appearing in line >32 is-passed
andthe combinedchannels in line-‘110A would ¿be
filter andßlimiterSll and appears in line-34 as
a Wave. having a meanA frequency? of 12 megacycles 60 'used to operate la reactance tube modulator 68.
tAlso, Vif désiredboth switchesßß andÄ‘E'dwrn-ay be
and having allof the'freque'ncy modulation char
act‘ër'isticsof ' the _- original one megacycle fre
closed„'one~or more signals may be `impressed
quency modulated wave appearing in linel I 4.
upon "oscillator'Z-ß'and one or more signalscon
currently may be impressed upon -oscilllatorïfâl
The _12 megacycle wave having, for example, a
maximumsyving of plus and minus 200 >kilocycles 65 As shown «in Fig. 2 the sameA resultant-¿modu
lating voltage may be used 'to simultaneously
and’ appearing in line- 34 _»_is fed intol a second bal
frequeneyfmoduiate both oscillators zalamiisa.
ancedrnixer or 'detectorßß alongk with oscillations
derive'dfrom a vsecond local oscillator 50 which
may be operating, _for example, at a frequency of
ISÍineg'a'cycles Aper second, _
_
„"Svvitcliedfto Noscillator'§50 by means of-switch
In this 'casa'howeven'the-phase of the resultant
voltage applied toltlie reactance tubemodulato-rs
70 lïßfandV 56r must be opposite so that the total fre
quency swingrof Vthe oscillatorskisthe sum offre
54 is `a reactance’tube modulator» 5E. fed with 'one
quency-‘swings'imparted to them.
or more signaling channels from channeling
-Morel'specifically -as shown in Fig.:=2', oscillator
27S- is Aprovided‘withi aa frequency controlling par
-
equipment lill4 and line 58,. Thus three separate
voice signals may be fed’ to the channeling equip 75 alle_l-'tuned circuit -ßll and oscillator'âßis;providéd Y
2,421,727
with a parallel tuned `frequency controlling cir-‘l
cuit 82. `The output of channeling equipment 60,
quadrature voltage derived from the tuned cir-1
cuits 3i),` v82 is impressed across the control grids'
through .the action of transformer 80' applies the
resultant modulating potentials oppositely to the
and cathodes of `tubes 68, 56. l
control :grids of the reactance tubes 55 `and 08
through chokes 80 and88. The valves of fre
quency swing and mean frequency show-n on Fig.
2 are illustrative only and are not to be consid
,
l
‘
`
n i
a `variable capacitive` :reactance in shunt , to the
tune‘dwcircuits 80, ‘82' which may effectively be
grounded at'their lower terminals for high fre
quency currents> ‘by` large bypassing Condensers
ered in any way as restrictive ofthe present
invention.
,_
These tubes as connected in Fig. 2 will present
|08,\||0.
1i
1,
_,
‘
‘
.
The positions of Condensers |00, |ll2and re
sistors |04, .|05 may be reversed, in which case
the resistors should be blocked oil’ fromthe plates
’
As in connection with Fig. 1 rectangle 38 may
not only represent a ñlter network but also a
vacuum tube limiter. This islalso true of the
byseries .connected bypassing `Condensers of large
apparatus represented by rectangle 30.
value so as to prevent the plate voltage from
It should accordingly be clear that whatever 15 being applied to the grids While allowing A. C.l
frequency modulation exists in line le of either
components to reach the grids. , Also„in this case
Fig. l'o-r Fig. 2 is also completely present in line
the resistorsshould be large in value and the
00. In addition, as before explained, line ¿l0 also
Condensers |00.' |02 vwhen connected between the
contains the modulation >due to the channels
grids and filaments should be of large capacity
which are locally introduced through equipment 20 or relatively low capacitive reactance. With the
50"provided .at the relaying point. Since the
latter connections, tubes 06, B8 then` act as
modulationcappearing in line l0 is not subjected
variableinductances inshunt to the tuned cir
to complete demodulation so as to reproduce the
cuits 80, 82.`
‘
l
t
l
ultimate or elemental signals, cross talk due to
Having thus described my invention, what I
unlinearity of discriminators and modulators is 25 claim is:
l
,
not added to the “straight through” channels
l. The' method which includes receiving` a
that is, those received upon the receiving antenna
multiply modulated wave, subjecting the wave to
system 2, sand retransmitted over the retrans
a Ysingle demodulation, heterodyning i Waves
mitting antenna arrangement 4E, riß-even though
derived from the demodulated wave with signal
several channels are added to the “through wave”
at the relaying point as explained.
.My invention is not, of course, restricted to a
doubly modulated system such as referred to.
modulated oscillations,` ñltering waves resulting
from the heterodyning process, and transmitting
For example, the addition of channels to a relay
cludes subjecting a doubly frequency modulated
wave to a single frequency demodulaticn, hetero
dyning waves ,derived from'the demodulated wave
theñltered waves.
‘
2. The method of‘wave conversion which in--
system employing single frequency modul-ation
-may be accomplished in a similar way. vThus,
for" example, assume that the received waveßhas
with frequency modulated'oscillations, and trans
aï‘mean frequency of 3000 megacycles and has
mitting waves resulting from the heterodyning
been directly frequency modulated with an audio
channel covering a :band of frequencies from 16 40
3. The method which includes subjecting a-suc
cycles to 16,000 cycles and so that the maxim-urn
cessivelyY angle modulated wave; to an angle
deviation in the received 3000 megacycle Wave is
demodulation process, heterodyning Waves de#
plus and minus 2.5 megacycles. This wave i-s
rived from the dernodulation with an angle modu
received >at the relaying point and beat in appa
lated oscillation, and transmitting waves derived
` from the heterodyning process.
ratus 8 to an intermediate frequency of, for ex
ample, 30 megacycles $2.5 megacycles. This 30
4. The method of adding signal channels to «a
process.
oscillators as explained in connection with Figs.
1` and Z‘may be frequency modulated with one
or‘more new and different signals introduced at
‘
A frequency multiplier 400 may be inserted in
line 40 before transmitter 42 and following filter
and limiter 38. The effect of this multiplier will
Y
y
ï
\
wave which includes subjecting the waveto an
angle demodulation, l generating waves, angle
modulating the generated waves` with `Waves
representing one or more signal channels, hetero-`
dyning waves derived from the demodulation with
said waves which have been angle modulated with
megacycles and then ibeat black up to a higher
frequency such as to 60 megacycles with the sec
ond oscillator 50. `In this case either or both
l
‘
signal carrying, successively angle modulated
m‘e'gacycle` wave may then be heat to a low‘fre
quency-by oscillator 25 su-ch as, for example, l5
the relaying point.
.
one or more signal channels which are to be
55
added, and transmitting waves resulting from
the heterodyning process,
,
`
„
\
5. The method of relaying a signal carrying,
doubly modulated wave and adding one'or more
signal channels to the wave to be relayed which
sub-carrier and also its frequency deviation by 60 includes subjecting the doubly modulated wave
the multiplying factor, prior to use, for modula
to a, single demodulation, heterodynin-g waves de»tion in thefrequency modulated oscillator 42.
rived from the demodulation with a wave which
has been modulated with one or more signaling
The balanced mixers 28 and 3E of Figs. 1 and
2 are preferably of the type sho-wn in Fig. 9 of
channels to be added, ñltering the heterodyned
be to increase the mean frequency of common
my (3o-pending application involving the mixer 65 waves, generating a high frequency carrier, and
modulating the high frequency carrier with the
tubes 904, 906, oscillator tube 908 and their yasso
elated circuits.
filtered waves.
6. The method of relaying a signal carrying,
The reactance tubes 56, 68 may, of course, be
four ‘element screen grid tubes or they may be
doubly angle modulated wave and addingone` or#
pentode tubes. Condensers |00, |02 lare shown 70 more signal channels to the Wave to‘be relayed
as _connected between the plates and control grids
which includes subjecting the doubly angle modu
and they should, therefore, have relatively high
lated wave to a single angle demodulation, hetero
reactance at the operating frequencies of oscil
dyning the waves derived from the angle demodu
lators 26 and 50 respectively.
Resistors |04, |06 ,
are'of relatively low value. ` In this Way‘e?fective
lation with a wave which has been angle modu
5 lated with one'or more signaling channels to be
'
2,421,727
7
8
ing waves derived from the demodulation> with
added,` filtering the. heterodyned waves, generat
an oscillation which has been frequency modu
ing' a high frequency carrier, and angle modulat
ing the hi-gh frequencyv carrier with the filtered
lated with one or more signal channels, -a filter
for filtering a band of waves fromrthe hetero
Waves.
dyned waves, apparatus for heterodyning the
7. The method of relaying a signal carrying,
doubly frequency modulated Wave and adding. one
filtered band of Waves to waves having different
meanfrequency than said filtered band, a gener
or more signal channels» to the Wave to be relayed
ator for generating a high frequency carrier, and
circuits operating to frequency modulate the gen
tion, heterodyning the waves derived from the 10 erated carrier With the heterodyned waves of kdif
ferent mean frequency.
frequency demodulatlon with awave which has
13'. Relaying apparatus including means for
been frequency modulated with one or more sig-receiving a signal carrying, doubly frequency
naling channels to be added, filtering the hetero
modulated wave, a demodulator system forv sub
dyried waves, generating a high frequency carrier,
and frequency modulating the high frequency 15 jecting the received wave to a single frequency
demodulation, means for heterodyning the de
carrier with the filtered waves.
modulated Wave to anintermediate frequency, a
8. The method of relaying which includes re
filter filtering the intermediate frequencyY wave,
ceiving a signal carrying, doubly frequency mod
means for heterodyning the filtered wave with
ulated Wave; subjecting the receivedrvvave to a
which includes subjecting the doubly frequency
modulated wave to a single frequency demodula
singlefrequency demodu-lation, heterodyning the 20 an oscillation which has been frequencymodu
lated with waves representing one or more sig
demodulated wave to an intermediate frequency,
nal channels, means for generating a high fre
quency carrier, and means for frequency modu
odyning the filtered wave with an oscillation
lating the high frequency carrier with waves de
which has been frequency modulated with bands
of frequencies representing one or more signal 25 rived- from the last-mentioned heterodyning
filtering the intermediate frequency wave, heter
channels, generating a high frequency carrier,
and> frequency modulating the high frequency
process.
_
14. Means for relaying a signal carrying, doubly
frequency modulated wave and adding one or
carrier with waves» derived from the last-men
tioned heterodyning process.
9`; The method of relaying which includes re
more signal channels to the wave to be relayed
which
includes means for subjecting the doubly
30
frequency modulated wave to a single frequency
ceiving a signal carrying, doubly frequency mod
demodulation, means for heterodyning the Waves
ulated wave; subjecting the received wave to a
derived from the frequency demodulation with
single frequency demodulation, heterodyning
a- Wave which has been frequency modulated with
waves derived from the demodulation with an
oscillation which has been frequency modulated 35 waves representing one or more signaling chan
nels to be added; means for filtering and limiting
with one or more signal channels, filtering out ka
the heterodyned Waves, means for generating a
band of Waves from the' band of heterodyned
high frequency carrier, and means for frequency
Waves, heterodyning the filtered Waves to occu
modulating the high frequency carrier with the
pying a different position in the frequenßl7 Spec
trum, generating a high frequency carrier, and 40 limited and filtered waves.
15V. Apparatus for relaying a signal carrying,
frequency modulating the generated carrier with
doubly angle modulated wave and adding one
the heterodyned band occupying said different
or more signal channels to the wave to be relayed
position.
which includes demodulating apparatus operat
l0. The method of relaying which includes re
ing to subject the doubly angle modulated Wave
ceiving a signal carrying, doubly frequency mod
to a single angle demodulation, a mixer for
ulated wave; subjecting the received Wave to a
heterodyning the waves derived from the angle
single frequency demodulation, successively het
erodyning the demodulated waves with two lo
cally Ygenerated ` oscillations, oppositely frequency
modulating the locally generated oscillations
demodulation with a wave which has been angle
modulated with Waves’representing one or more
50 signaling channels to be added, a filter filtering
the heterodyned Waves, an oscillator generating
a high frequency carrier, and a modulator for
4with bands of frequencies representing one or
more signaling channels, generating a high frea
quency carrier, and frequency modulating the
angle modulating the high frequency carrier with
high frequency carrier with waves derived from
the filtered waves.
the'seoond heterodyning process.
11. Relaying apparatus comprising means for
receiving a signal carrying, doubly frequency
55
Y
16. Apparatus for relaying a signal carrying,
doubly modulated wave and adding one or more
signal channels to the wave to be relayed com
modulated wave,. a discriminator-detector cir
cuit for subjecting the received waves to a Single
pri-sing a-demodulator for subjecting the doubly
generating
the demodulationwitha signal modulated Wave,
modulated wave to a single demodulation, a
frequency demodulation, a pair of generators for 60 mixer for heterodyning the waves derived from
two high, frequency oscillations,
a filter Afor filtering the heterodyned Waves, a
generator for generating a high frequency car
rier, and a circuit for modulating theV high fre
circuits for oppositely frequency modulating the
two generated oscillations with waves represent 65 quency carrier with the filtered Waves.
17. Apparatus for adding signal channels to
ing one or more signaling channels, means for
a successively angle modulated wave comprising
generating a high frequency carrier, and means
a demodulator for subjecting the wave to an
for frequency modulating the high frequency car
angle demodulation, a mixer for heterodyning
rier with Vwaves derived from the second hetero
Waves
derived from the demodulation with a
dyning process.y
70
wave which has been angle modulated with waves
12. Relaying apparatusl including means for
representing one or more signal channels which
receiving a signal carrying, doubly frequency
are to be added, filtering and limiting apparatus
modulated wave, a discriminator-detector cir
to filter and limit the ,output of saidV mixer and
cuitI for subjecting the received Iwave to a single
frequency demodulation, means for'heterodyn 75 means for utilizing the filtered and'limited'waves.
means for successively heterodyning the demod
ulated waves with waves from the two generators,
2,421,727
18. In combination, means for subjecting a
successively angle modulated wave to an angle
demodulation process, means for heterodyning
waves derived from the demodulation with an
oscillation which has been angle modulated in
accordance with the Wave output of one or more
signal channels, a limiter for limiting the heter
odyned waves, and a circuit utilizing waves de
rived from the heterodyning process.
10
tion, modulated in accordance with waves repre
senting one or more bands of frequencies, and
means for utilizing the Waves resulting from
the heterodyning process.
`
20. In combination, means for receiving a mul
tiply modulated Wave, a demodulator for sub
jecting the wave to a single demodulation, a
mixer for heterodyning the demodulated Iwave
with an oscillation which has been modulated
19. In combination, means for subjecting a 10 with waves representing one or more bands of
doubly frequency modulated Wave to a single
frequencies, and a circuit utilizing the wave re
frequency demodulation, means for heterodyning
the demodulated wave with a modulated oscilla
sulting from the heterodyning process.
LELAND E. THOMPSON.