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Патент USA US2408078

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Sept. 24, 1946.
Filed Aug. 25. 1944
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3 Sheets-S0“, 1
_ f Ryn/. 1.6
,Sept 24, 19.46.
Filed Aug. 25, 1944
3 Sheets-Sheet 2
(21 D,
Sept. 24,- 1946.
Filed Aug. 25, 1944
3 Sheets-Sheet 5
v 66
I/ l
Patented Sept. 24, 1946
» Emile Labin, New York, N. Y., assignor to Federal
Telephone and Radio Corporation, New York,
N. Y., a corporation of Delaware
Application August 25, 1944, Serial No. 551,202
15 Claims.
(Cl. 179-15)
plaining the operation of the embodiments shown
Thisinvention relates to multi-channel com
municating system and more particularly to sys
tems for transmitting in interleaved manner the
in Fig. 4.
time modulated pulses of a plurality of channels.
One of the objects of the invention is >to pro
may comprise-the Vtransmitting equipment for a
two-way multi-channel communicating system or`
it may be usedïas a multi-channel broadcasting
j ,_
The multi-channel transmitter shown in Fig.V 1
vide a multi-channel transmitter and method for
either multi-channel transmission to a second
" system for selective reception of the channels by
terminalor for multi-channel broadcasting from Y
individual receivers. Y In the case of multi-chan
a given station for selective reception by indi
nel broadcasting the transmitter, -of course, will
vidual receivers.
10 be provided with a suitable omni-directional kan
Another object of the invention is to provide a
tenna. For >simplicity of illustration the system
new method and means for time modulating a
is shown for three transmitting channels, I, 2
train of pulses.
and 3, although many additional channels may
In most multi-channel communicating systems
employing pulse time modulation, each channel
be included, if desired.
The embodiment shownin Fig. 1 includes aV
is provided with an individual time modulator.
stable type ofpulse producer 4 of known form
VAccording to one Vof the features of »my invention
I provide a single time modulator for all of the
for producing a train of pulses such as indicated
at 5 in graph a of Fig. 2. The repetition rate of
the pulses 5 is selected in this embodiment as that
channels. A pulse train corresponding to the
interleaved pulses vof all the channels is applied V20 pulse rate desired for a single channel. The
pulses 5 are multiplied according to the number
to kthe modulator and the signal energy of each
of channels desired by applying the pulses to a
channel is divided into spaced pulse segments
-pulse multiplier 6 of known character which may
timedv diiferently for the diiferent channels, the
or may vnot include a pulse shaper. Preferably
pulse segments of the signal energy of all the
channels being applied in interleaved manner to 25 the output pulses 1 of multiplier 6 are narrow
the'time modulator as the modulating energy.
pulses as indicated by graph c.
Energy of the pulses 5 is also applied to a pulse
shaper 8 to produce pulses> of a desired width as
accordance with the amplitude of the correspond
indicated at 9 in graph b. The pulses 9 are used
ing pulse segments. 'I'his method of modulation
may of course be employed for a single channel 30 for two purposes, one for selecting spaced por
tions of the signal energy of each channel, and
where desired, one of the advantages of such a
The pulses of the train are displaced in time in
system for a single channel, or even for multi
the other for synchronizing receivers.
channel transmission, being that the interval be
tween pulse segments of any one channel may be
blocked at the receiver thereby insuring a high
signal-to-noise ratio. Another advantage of the
system particularly in multi-channel operation
The synchronizing pulses may be differently
shaped, if desired by applying pulses 5 to pulse
shaper 8a through connection 8b. In the present
showing, however, the same pulse. width is used
for synchronizing purposes and for selecting seg.
ments of signal energy. The output pulses 9 Vof’
shaper 8 areapplied to a delay network I0 having
output connections I I spaced'> at diiferent retarda
tion points therealong whereby pulse energy may
be supplied at -diñîerent time intervals correspond
ing to the timing desired for pulses of the diiîer
ent channels. The output connection for channel
is a reduction in the number of time modulators
required by such systems heretofore proposed.
For a lfurther understanding of the invention,
reference will be had to the following detailed
description to be read in connection with the ac
companying drawings, in which:
Fig. 1 is a block diagram of a multi-channel
transmitter'in accordance with the principles of
this invention;
Fig. 2 is a graphical illustration useful in ex
plaining the operation of the transmitter of
I is applied to an amplifier I2V which is normally
blocked. The signal source I3 for channel I is
also applied to the amplifier I2 but the blocking
potential for the Yamplifier is so chosen that ythe
signal energy _remains blocked regardless of its
Fig. 3 isa schematic Vwiring diagram of a pulse 50 variations in amplitude.L The retarded or keying
pulses from output connection Ilaunblock the
time modulator that may be yused in the system
amplifier for the duration of-each of the pulses.
of Fig. 1;
i e _
`This 'passes a segment of the signalv energy, -or
Y Fig. 4 is a block diagram of a further embodi
Fig. 1;
ment of the invention, and
Fig. 5 is a -graphical illustration used inex
rather producesin effect an output pulse lwhich
55 is amplitude modulated in accordance with the
segment of signal energy coincident with each
signal pulses of graph d which vary in amplitude
keying pulse.
in accordance with segments of the signal energy
are applied over connection I8 to the anode cir
cuit 29 of an amplifier 30 to Which is applied over
connection BI the pulses 'I' from pulse multiplier
5. The source of anode voltage is applied through
the resistor 32 and the retardation circuit 25.
In graph b, for example, the pulses I4, I5 and
I6 represent three successive output pulses from
~ amplifier i2 which are representative segments
0f the signal envelope I'I. These signal pulses
thus define points along the signal envelope I1
Should the impedance of coil 26 be sufficient the
as indicated.
The output pulses of each of the amplifiers of
the different channels are applied over connec
tion I8 to a time modulator I9 to which is also
applied the pulses l, graph c. The signal pulses
resistor 32 may be omitted.
The instantaneous signal value of the signal
envelope Il at the occurrence of pulse I5 is
reater than the minimum value at the occur
of the dii-ferent channels are interleaved in` ac
rence of pulse I4, and therefore produces greater
cordance with the retardation applied thereto
in delay device le. Pulses I4, .I5 and I6 are shown
to be retarded an amount t1 causing them to Coin
cide with the pulses of channel I. For channel 2
retardation eiîect on pulse Ib by a total amount
-equal to T`-|-./_\.t. This greater retardation of the
pulses I b over pulses Ia is produced by a change
in permeability of the core of coil 26, which alters
the pulses 9 are retarded an amount t2 for coin
the inductance of the circuit 25. The still greater
signal value represented by pulse Iâ produces a
therefore, that the amplitude modulated pulses 20 still greater retardation for pulses ic which equal
cidence with pulses of channel 2. It will be clear,
to T-1-2At. From the foregoing it is believed clear
that as the signal energy increases still further,
the greater the time displacement Will be for the
corresponding pulses of channel I. The time dis
character capable of displacing in time the pulses
‘I in accordance with the amplitude 4of the corre 25 placement according to this method of modula
tion is of course small but small displacements
sponding pulses applied over connection I8. Two
are of advantage in multi-channel communica
examples of time modulators of this character
tion since a larger number of pulses is possible for
are hereinafter described in connection With Figs.
of each channel coincide in time With pulses of
the pulse train 1 of graph c.
The time modulator I9 _may be of any desired
3 and 4.
Graph e of Fig. 2 illustrates the time displace
ment produced on the pulses of channel I by the
pulses I 4, I5 and. I6 of graph d. The loW or
minimum amplitude of pulse I 4, which may be
regarded as corresponding to the maximum nega
tive signal value, is indicated as having retarded
pulse Ia of channel I an amount T. This mini
mum amount of retardation for pulse I4 may be
regarded as always present in the time modula
tor. The amplitudes of pulses I5 and I6 are
shown to time displace the pulses Ib and Ic
amounts T-l-At and T-1-2At respectively, since
they are of successively greater signal values. It
will be clear that the time displacements of the
pulses of the several channels vary in amounts
according to the instantaneous values of the cor
responding signal energies, and that the displace
ments are relative to the pulse positions of train
'I in the absence of modulation or with respect
to the positions of the pulses S of the synchroniz
ing channel (graphs f and g).
The pulse energy 9 from Shaper 3 is applied
over connection 29 to a clipper mixer 2l to which
is also applied the time modulated pulse output
of modulator I8. The synchronizing pulses being
a given time interval.
For a further discussion
of this principle of time modulation reference
may be had to my copending application Serial
No. 546,378 filed July 24, 1944.
In Fig. Ll ï show an embodiment of the inven
tion wherein pulse producer 33 is arranged to
produce pulses .at the repetition frequency desired
for all of the channels taken together. The pulse
output of producer 33 is represented by the pulse
train 34 in Vgraph m of Fig. 5. To obtain the
pulses for each channel, the pulse train 34 is
40 applied t0 a pulse divider 35 whereby pulses 36,
graph 11, are produced. These pulses are then
applied through a pulse shaper 31 to a delay net
Work 38 similar to the device I0 in Fig. l. The
pulse energy 3S is thus shaped and delayed for
channel I as indicated by the pulses 39, 40 and
4I of graph o. These Wider delayed pulses are
applied to channel amplifier 42 for selecting a
segment of signal energy from source 43 in the
manner hereinbefore described. The output
pulses 39, 49, 4I of amplifier 42 are thereafter
applied to a clipper gate 44, for translation of the
amplitude modulation thereof into time modula
If a time modulator of the character shown in
Fig. 3 were employed in the system of Fig. 4, the
pulses 34 would be applied directly thereto as
hereinbefore described in connection with Fig. l.
Before application of pulse energy 34 to clipper
gate 44, it is desirable to reshape the pulses into
chronizing pulses S, the resulting train of pulses 60 pulses each having at least one inclined edge cor
for transmission being as shown by graph g.
responding in time to one of the pulses of the
These pulses are applied to transmitter 23 for
several channels. The energy of the pulse train
transmission at a given carrier frequency over
34 is therefore applied t0 a Wave producer 45 of
the type capable of producing a zig-Zag shaped
antenna 24 which may be of a directional or
omni-directional type.
Wave 4B, the undulations of which are shown in
graph p, symmetrically shaped. The wave, of
Referring to Fig. 3 a pulse time modulator is
course, may be varied considerably, and if desired
shown that may be employed as the time modu
may be of the saw-tooth form having one edge of
lator I9 in Fig, 1. The time modulator comprises
each tooth inclined and the other edge thereof
a retardation circuit 25 having an inductance
the same as pulses 9 in graph b as to Width and
timing coincide with pulses of a fourth chan
nel in the train of pulses l. By providing the
mixer 2l With a limit clipping level indicated at
22 in graph f the pulses 4 are replaced by syn
coil 26 with a core of iron or other permeable
material, and condensers 21, 28.
The minimum retardation characteristic of the
substantially vertical.
Various types of clipper gates may be employed
at 44, the example shown being of a type having
circuit 25 may be represented by the time inter
two dry rectiiiers 47 and 48. The two rectiñers
val T of graph e, Fig. 2 for a maximum negative
are connected back to back and a small positive
signal value such as indicated by pulse I4. The 75 voltage is applied over resistor 49 to the inter
" '2,408,077
mediate point 50. The resistor 49 is -preferably
at least several times larger than the low “for
ward” resistance of the rectiñers, although it
for Vusein deblocking circuits of` the> receiving
For a more complete discussion of the time
should be low in comparison with'the high “back” ‘_ modulating principles of the clipper gate type of
resistance thereof. The input wave 46, graph p r5 VmodulatorV and of variations thereof, reference
is applied through coupling *condenserk 5|` to re
may be had to the copending- application of D. D.
Grieg and myself, Serial No. 455,898, filed August
sistor 52 which is preferably several times smaller
24, 1942.
thanA resistor 49. The output of the circuitV is
delivered across resistor 53 which maybe of the
same order of magnitude as resistor 52,
For modulating the clipping action the am
plitude modulated pulses such as 39, 40, 4|,- etc.,
of channel I are applied through resistorY 52 to
From the foregoing description it is clear that '
10 I have disclosed a multi-channel communicating
system requiring a single time modulator for a
plurality of channels. Also, I have shown two
diiîerent methods of producing the train of pulsesA
rectifier 41. The relationship between clipping
to vbe time modulated and - a second train of
levels 41a, 48a of the clipper gate vand wave 46 k15 pulses, energy of’which is used for each of the
shown in alignment with the pulses of the fourth
channels to obtain segments of the signal energy
channel, graphs m and p, Fig. 5, represents the
of the different channels. While I have indicated
condition when the amplitude modulated pulse ' a base pulse producer from which these two trains
input- is of- an amplitude corresponding to the
are obtained it will be clear that in the'place of
maximum negative value of the signal energy for 20 a base pulse producer I may use a stableY oscil
such channel. The action of the two rectiñers
lator for producing a sinusoidal wave havingthe
Y is that of limiting the passage of input wave 46
frequency desired for either train of pulses. By
between levels 41a and 48a. The application of
using a frequency multiplier or divider a wave of
energy to -the circuit through resistor 52 operates
the frequencydesired for the 4otherrpulseftrain
to vary the location'of these two levels relative 25 may be obtained. The pulses may thereafterbe
to the amplitude Yof the wave 46.
produced from'these two waves according to well
This double limit clipping results in Va rec
tangular or trapezoidal wave form suchv as in
dicated in graph q. This rectangular wave is
applied to a diiïerentiator 54 which converts each
rectangular pulse portion of the wave into alter
nately positive and negative pulses as indicated
by graph r. It will be noted that the rectangular
pulse portion 55 corresponding to the clipping of
known methods.
While I have shown and described particular
embodiments of the present invention, it is’recê
ognized, of course, that many variations and dif
ferent embodiments may be made without de
parting from my invention. It is therefore to be
understood that this description is given by way
wave 46 in alignment ywith channel 4 produces a
of example only and not as a limitation on the
scope of the invention as set forth in the objects
narrow pulse which, when generated, producesY
thereof and the accompanying claims.
positive and negative pulse 55a and 55h. The am
plitude modulatedrpulse 39 of channel I shifts
the clipping levels of gate 44 to a lower portion
56 on Wave 46. This produces a wider pulse 51
than the pulse 55. Thegincreased width of pulse
I claim:
l. A method of multi-channel transmissie
comprising producing a train of pulses, segregat
ing spacedsegments from the signal energies of
a plurality of channels, differently timing the
51 over pulse 55 corresponds to the increased
segments of the different channels to interleave
signal value represented by the amplitude of , them together into a series of segments wherein
pulse 39. Accordingly, the pulses 51a and 51h
. each segment corresponds to a pulse of said train.,
:are separated by a time interval corresponding to ' 45 and time modulatingr the pulses of said train ac
the width of pulse 51. Likewise pulses 58d and
cording to the amplitude of the corresponding
58h resulting from pulse 58 are displaced a greater
signal segments.
time interval corresponding to the greater am
2. A method of multi-channelV transmission
plitude of pulse 46, and the still greater pulse
comprising producing. a plurality of` series of
width 59 resulting from> the clipping produced by 50 vpulses differently timed so that the pulses of the
pulse 4| produces pulses 59a and 59h having a
diñ‘erent series interleavein time, -producing a
wcorresponding greater time displacement. 'I'he
trainof pulses corresponding to said plurality of
pulses of graph r are applied to a threshold clip
series taken together, translating `the pulses of
per circuit 6B by which pulses 551), 51h, 58h,
each series into signal pulses the amplitude of
etc., are clipped at level 6l. Of course, pulses 55 which Vary according to the instantaneousvalues
55a, 51a, 58a, etc., may instead be clipped where
of the signal energy of a corresponding'channel,
by the time displacement of the output pulses
and timemodulating the pulses of said train ac~'
will be in the opposite direction.
cording to the amplitude of the corresponding
The output of the clipper 60 is applied to a
signal pulses.
mixer 62 to which is also applied synchronizing 60 3. A method of multi-channel transmission
pulses 64 obtained by shaping the pulse output
comprising producing a train of pulses of a given
of pulse divider 35 at shaper 63. The synchroniz
repetition frequency, dividing the pulse energy
ing pulses 64 are shown in graph s to coincide
of said train to obtain a series of pulses of a lower
repetition rate such as may be desired for chan
with pulses 55h produced from the pulses of
channel 4, and since the mixer 62 is preferably 65 nel communication,V retarding by diiîerent
amounts the energy of said series of pulses to ob- ,
of the character having a limit clipping level 65,
the synchronizing pulses 64 replacethe pulses
, 55b. This results in a train of pulses indicated by
tain a plurality of series of Vpulses of different
timing so that they interleave in time similarly
`as the pulses of said train, translating .the pulses
graph t in which the synchronizing pulses 64 70 of each series into signal pulses the amplitudes ‘
are of a width greater than the pulses of the
of which vary according to the instantaneous
channels I, 2 and >3. This greater width of the
valuesof the signal energy of the corresponding
synchronizing pulses >makes it possible for the
channel, and time modulating the pulses of said
receiver to segregate the synchronizing pulses
train VVaccording to the amplitude of the corre
from the channel pulses by width discrimination 75 sponding signal pulses.
4.'A method of multi-channel transmission
comprising producing a series a pulses of a repe
tition rate desired for channel communication,
multiplying the pulse energy of said series to ob
tain a train of pulses having a repetition fre
quency corresponding to a given plurality of
' 8
position of the pulses and means for applying the
signal pulses of varying amplitude to said delay
means to vary the retardation effect thereof on
the pulses of said train.
10. A system according to claim 7 wherein the
means for time modulating the pulses of said
train includes means for producing a zig-zag
channels, retarding by diiîerent amounts the en
shaped wave from said train thereby providing
ergy of said series of pulses to obtain a plurality
triangularly shaped undulation having at least
of series of pulses of different timing so that they
interleave in time 'similarly as the pulses of said 10 one inclined edge to correspond to each pulse of
said train, means for gate clipping the undula
train, translating the pulses of each series into
tions between two levels, means for varying the
signal pulses the amplitude of which Vary accord
clipping levels of the gate clipping means rela~
ing to the instantaneous v‘alues of the signal en
tive to the amplitude of eac‘n undulation accord
ergy of a corresponding channel, and time modu
lating the pulses of said train according to the 15 ing to the amplitude of the corresponding signal
pulse, and means for differentiating the clipped
»amplitude of the corresponding signal pulses pro
portions of the undulations to obtain pulses, the
duced from said plurality of series.
time positions of which represent the time posi
5. A method of time modulating pulses com
tion of the clipped portion of .the corresponding
prising producing a ñrst train of pulses varying
inclined edges of said undulations.
in amplitude according to the instantaneous val
11. A multi-channel transmission system com
ues of ` a given signal energy, producing a second
prising means for producing a ñrst train of pulses,
train of pulses having a repetition frequency cor
means for producing a second train of pulses the
responding to the repetition frequency of the
repetition frequency of which is a multiple of the
amplitude modulated pulses, and time modulat
ing the pulses of said second train according to 25 repetition frequency of said iirst train of pulses,
retardation means for retarding the pulse energy
the amplitude values of the corresponding pulses
of said first train 0i pulses to produce a plurality
of said ñrst train.
of 'series of pulses diiîerently timedl so that the
6. A system for time modulating pulses Corn
pulses taken together correspond to the pulses of
prising means for producing a train of signal
pulses of a given repetition frequency, the pulses 30 said second train, separate means for varying the
amplitude of the pulses of each series according
of which vary in amplitude according to instan~
to the instantaneous values of the signal wave of
taneous values of a given signal wave, means for
a corresponding channel, and means to time
producing a second train of pulses having said
modulate the pulses of said second train accord
>repetition frequency, and means for varying the
ing to the amplitude values of the pulses of said
time positions of the pulses of said train in ac
plurality of series.
cordance with the amplitude values of the corre
12. A system according to claim 11 wherein the
sponding signal pulses.
means Íor'producing the pulses of the second
7. A multi-channel transmission system com
train includes means for multiplying the pulses
prising means for producing the plurality of »series
of pulses differently timed so that the pulses of 40 of said ñrst train.
13. A system according to claim 11 wherein the
said plurality of 'series interleave in time, means
means for producing the pulses of said first train
for producing a train of pulses corresponding to
includes means for dividing the pulses of said
said plurality of series taken together, means for
translating the pulses of each series into signal
pulses the amplitudes of which vary according to
the instantaneous values of the signal energy of
a corresponding channel, and means for time
modulating the pulses of said train according to
second train.
14. A system according to claim 1l wherein the
means for varying the amplitude of the pulses of
each series includes a normally blocked ampliñer
for the signal energy of each channel and means
to apply one of said series of pulses to unblock
8. A system according to claim '7 wherein the 50 each said ampliñer for the duration of each pulse
of such series.
means for translating the pulses of each series
15. A system according to claim 1l further in
into signal pulses includes a normally blocked
cluding means to produce a synchronizing pulse
ampliñer for the signal energy of each channel
channel comprising means for mixing the pulses
and means to apply one of said series of pulses
of said first train with the time modulated pulses
to unblock each said amplifier for the duration
of said second train, the pulses of said first train
of each pulse of such series.
being distinguished in width from said time
9. A system according to claim '7 wherein the
modulated pulses.
means for time modulating the pulses of said
train includes delay means for retarding the time
the amplitude o1“ the corresponding signal pulses.
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