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June 13, 1950
Filed Feb. 25, 1945
3 Shee'ts-Sheet 1
Ä' /fÑ/ll/SE
June 13,v 1950
Filed Fel» 23,> 1945.
5 Sheets-’Sheet 2
BY ß ì
. June 13', 1950
Filed Feb. 25, 1945
3 Sheets-Sheet 3
112g. Ó:
BY ß /Áíy
Patented June 13, i950
Irving A. Krause, Jersey City, N. il., assigner to
Federal Telephone and Radio Corporation, N ew
York, N. Y., a corporation ol’ lìelaware
Application February 23, 1945, Serial No. 579,353
3 Ulairns. (Cl. E50-27)
This invention relates to radio reception of
signal pulses and more particularly to the re
ception of T. M. (time modulated) signal pulses
of the “push-pull” type.
By “push-pull” T. M., I have reference to that
type of pulse time modulation where alternate
pulses are displaced in time toward and away
from each other according to substantially the
tion and the trigger circuit responds to the saw
tooth potential when it reaches the voltage level
at which the circuit is biased. The shaping op
eration may then be controlled by the charac
teristics of the trigger circuit, such as by first
producing a substantially square wave which is
suitably shaped by a condenser-resistor network
or other pulse shaping circuit.
instantaneous values of a signal wave. The
Still another feature oi the invention includes,
pulses in the absence of modulation may be sym 10 besides the delay and shaping of signal energy
metrically or unsymmetrically spaced, that is
in one circuit, a similar shaping of the signal
to say, the pulses are equally spaced for syn pulses in a second circuit without imposing any
particular delay and then combining the two
metrical operation and for unsymmetrical oper
shaped pulses. The pulse shape in this form is
ation, they are given an initial offset spaced re
lation. For demodulation oi the time modulat 16 preferably substantially triangular, whereby the
two pulses when combined create a composite
-ed pulses, the time displacements thereof are
pulse of an amplitude corresponding to the de
translated into amplitude displacements for ap
gree of time displacement of the two pulses. Re
plication to audio utilization apparatus.
gardless of the type of delay, re-shaping and
It is an object of my invention to provide a
novel method and
for demodulating and 20 combining operation, the signal component
present in the resulting composite pulse energy
translating time modulated pulses of the “push
may be obtained by either a threshold clipping
pull” type into amplitude modulation energy.
amplifier or by a peak riding clipper.
Another object oi my invention is to provide
For a better understanding of the objects and
a method and means for utilizing the energy of
each signal pulse to demodulate the time dis 25 features of the invention, reference may be had
to the following detailed description in connec
placement of a following pulse.
tion with the accompanying drawings in which:
Still another object of my invention is to pro
vide a method and means to cause energy of
each pulse to coincide 'with energy of a follow
Fig. 1 is a block diagram of a radio receiver
according to my invention;
Figs. 2 and 4 are graphical illustrations use
ing pulse to effect translation of the combined 30
ful in explaining methods of operation of the re
time displacement of the pulses into amplitude
displaced energy.
ceiver of Fig. 1;
Fig. 3 is a block diagram of a variation oi the
According to one feature of the invention, a
demodulating pulse is produced in response to
receiver of Fig. l;
each signal pulse wherein the demodulating 35 Fig. 5 is a circuit diagram or" the delay and.
shaping units of the receiver of
l; and
pulse includes a voltage variation characteris
Fig. 6 is a graphical illustration useful in ex
tic, and has the time displacement of the initiat
plaining the operation of the receiver when the
ing signal
but which is retarded in time
circuit oi Fig. 5 is included therein.
so as to coincide with a following signal pulse.
Referring to Figs. l and 2, l have shown the
The demodulating pulse thus produced is com 40
receiver of Fig. i to inclu-de a carrier receiver
bined with the following signal pulse thereby
and detector l which may be of any known' char
producing a composite pulse, the peak oi’ which
acter for receiving pulse modulated carrier fre
represents the signal component oi the two pulses.
quencies over antenne. 2 and for removing the
The production of the demodulating pulse
carrier component. A detected train of pulses
may follow any one of several different methods.
3, f-l, 5, li etc. such
illustrated in graph A in
In one method the energy of the signal pulses is
Fig. 2 is applied over circuits ‘l and il to thresh
delayed the desired amount and then re-shaped
old clipper
The circuit l includes a switch
t0 provide the desired voltage variation charac
arrangement lil, il whereby the pulse energy
teristic. in still another method, the energy of
may be applied directly to the threshold clipper
the signal pulses is employed to produce sa ~
over connection i2 or through a Shaper i3, the
tooth undulations which are in turn applied to
a multi-vibrator or other triggerable circuit bi
purpose of which will be hereinafter described.
The circuit t applies the pulse energy to a de
ased preferably for trigger operation at a level
lay device
and a Shaper l5 before application
depending upon the amount of delay desired.
Each signal pulse initiates a sawtooth undula día? to the threshold Clipper 9.
It will be noted in Fig. 2 that the pulses of graph
ference energy occurring between signal pulses
A are shown to have an initial offset relation, the
except for interference that may be of relatively
large amplitude and coincide with the peak por
tions of the triangular pulses. Graph D shows
average timing characteristic Ta is measured be
tween one of the extreme limits of modulation.
the clipped energy as indicated at 311-4, for ex
To represents the maximum limits of time modu
ample, whereby the signal envelope at 2I may be
lation of the pulses relative to their midposition
obtained by applying the output of clipper 9 to a
such as represented by the position of pulse 3.
low pass ñlter 22 for application to earphones 23
Pulses 4, 5 and S are shown to be displaced in
or to the utilization apparatus.
time from the mld-position of pulse 3, in push
pull according to a progressively decreasing nega 10
If desired, the threshold clipper S and ñlter 22
of Fig. l may be replaced by an amplifier 24 and
tive swing of signal potential (see curve 2I of
a peak riding clipper 25 shown in Fig. 3. The
graph D, Fig. 2).
ampliñer in this instance would not be biased for
Assuming that the switch arrangement Il), II
clipping operation but would pass the energy re
is in the position shown, the pulse energy applied
to clipper S will be substantially as shown in 16 ceived from circuits ‘I and 8 substantially as illus
graph A. The pulse energy applied to clipper 9
through circuit 8, however, is ñrst delayed as in
dicated by graph B, the delayed pulses being iden
tiñed as 3a, 4a, 5a etc.
trated in graph C oi Fig. 2. The peak riding clip
per 25 would then be controlled by the peaks of
the composite pulses such as represented by the
superimposed pulses 4, 5 and E whereby the signal
The Shaper I5 may be of any known character 20 envelope def-.ned by the pulse peaks is obtained.
Referring to Fig. 4, I have shown in graph E
capable of re-shaping the delayed pulse energy
to produce a pulse having oppositely disposed volt
three pairs of signal pulses 25, 2l; 28, 29; and 3D,
age variation such as indicated by the triangular
pulse shape 3b, curve C. It will be understood,
of course, that the time delay Tf1 will depend upon
the character of the delay device I4 and possibly
also of the shaper I5. When the triangular
pulses 3b, 4b, 5b etc. are combined with the cor
3l to illustrate the operation of the receiver of
Fig, 1 when the switch arrangement ID, II is
changed to pass pulse energy through the Shaper
It will be understood, of course, that in a
train of pulses including the pairs or” pulses shown
in graph E, that a large number of pulses will
occur in the intervals ‘between pairs, the three
responding signal pulses 4, 5, 6 etc., the latter are
superimposed thereon as indicated in graph C. It 30 pairs being selected and shown in three repre
sentative time modulated positions for illustra
will be observed that the alternate pulses are
tion of the invention. For example, pulses 26 and
superimposed on opposite sides of alternate tri
21 are shown displaced to extreme positions to
angular pulses. For example, pulse 4 is super
ward each other to represent maximum positive
imposed on the left hand side of triangular pulse
3b and pulse 5 is superimposed on the right hand 35 signal energy, pulses 23 and 29 are shown in the
positions assumed in the absence of modulation
side of triangular pulse 4b. Since the time mod
and pulses 38 and 3l are shown in the extreme
ulation is of push-pull character, the pulses 4 and
positions spaced from each other representing
5, when displaced away from each other descend
maximum negative signal energy.
on the inclined portions of the corresponding
Referring particularly to the portions of graphs
pulses 3b and 4b. When the alternate pulses are 40
F, G, H, and I, below the pulses 26 and 21 of
displaced toward each other, they ascend on the
graph E, pulse 2l is shown after re-shaping as a
corresponding alternate triangular pulses.
The push-pull displacement of the signal pulses,
triangular pulse 27a. Pulse 26 is shown to be
similarly re-shaped at 26a and delayed an in
however, is also retained by the triangular pulses.
By way of example, the triangular pulse 3b is Ll terval Td. Since the two pulses 26 and 21 are
in a position representing the extreme degree of
shown in broken line in a `position I5 which it
modulation for a positive signal, the re-shaped
would assume should the delayed pulse 3a occur
in the extreme position indicated at I 1, graphs
pulses 26a and Z'Ia thereof coincide to produce
A and B. Should this displacement take place
a maximum pulse 32 which, when subjected to
for pulse 3, a similar displacement would take ~
threshold clipping at level 20 by clipper 9 re
place for pulse 4 thereby placing it on or near
sults in pulse 33.
the limit position indicated at I8 depending, of
Pulses 28a and 29a, which correspond to in
course, upon the modulating signal and the fre
put pulses 28 and 29 are displaced with respect
quency of recurrence of the signal pulses. The
to each other so that the degree of overlap pro
'combining action of pulse 4 and pulse 3b for these
duces a composite pulse 34 which is of less ampli
two extreme positions would then result in a pulse
tude than pulse 32. The threshold clipping op
peak I9 which would represent the maximum
eration with respect to pulse 34 provides an out
amplitude displacement corresponding to a maxi
put pulse 35.
mum time displacement. Thus, the displace
Triangular pulses 30a and 3Ia corresponding
ments of pulses 3 and 4 combine in eiîect to pro
to the pulses 3B and 3| overlap to produce a
duce Vthe resulting amplitude displacement en
composite pulse 36 which just reaches the thresh
ergy. This is of particular advantage since
old clipping level 2l) of tube 9. Since the time
small displacements of pulses are thereby doubled
position of pulses 30 and 3I represents the maxi
according to my invention. A small difference of
mum negative signal energy, Zero output for this
displacement for adjacent pulses will ordinarily 65 signal is to be expected, it being understood, of
occur due to a change in the modulating signal
course, that clipping level may be chosen at a
Wave between the points represented by the time
lower Voltage if desired, in which case a given
position of the pulses. This difference, however,
output will be obtained for the maximum nega
is averaged by the combining of alternate pulses
tive signal.
so that the output, in elîect, produces an ampli 70
It will be noted that the maximum pulse out
tude indication corresponding to a midpoint in the
put 33 does not represent double the area of
signal wave between signal pulses.
pulse 35. Thus, an integrating circuit for this
The threshold clipper 9 is provided with a bias
pulse output may not be proportional linearly to
so that it clips at a voltage level 20, thereby elimi
the original signal. However, this system may
nating the triangular pulse energy and any inter 76 be of use Where the Original signal is distorted to
R5, this desired symmetrical relationship may be
compensate for this effect. However, since the
amplitude of the output 4signals corresponds sub
stantially to the amplitude of the original signal,
closely approximated.
The broken line sawtooth wave [email protected] of graph K
represents the timing of the sau/tooth in rela
a ‘peak riding clipper such as illustrated in Fig. 3
may be employed at the -receiver in the place of
tion to sawtcoth wave Sill when the pulses are
modulated to the extreme positions represented
by the broken line it, graph J. This variation lof
sawtooth timing varies proportionately the tim
ing of the rectangular pulses d2 and likewise the
timing oi’ the triangular pulses
Thus, the tri
angular pulses retain the time displacement of
the signal pulses from which they are initiated
threshold clipper t.
Instead of triangular pulses, rectangular pulses
may be employed in the demodulation method
illustrated in Fig. 4. The rectangular pulses may
comprise the output of the multi-vibrator [email protected] as
indicated at lli?, Fig. 5. In such case the degree
of overlap will be directly represented in the
composite pulse area which varies according to
the time modulation ci the signal pulses, The
so that the displacement thereof operates in con
junction with the time displacement of the sig
nal pulse superimposed thereon to substantially
peak amplitud-e of the composite pulse portion
will, however, remain constant.
double the time displacement effect for transla
Referring to Figs. 5 and 6, I show a circuit to
perform a clipping and circuit operation that
may take place in units ld and iii in
i. The
circuit includes a sawtooth generator 3i to which
tion purposes.
It will be noted that the two positions repre
sented by the superimposed pulse indications 5l
and 52, graph M represent the extreme positions
of the superimposed pulses relative to the tri
angular pulses and that they occur on the upper
regions of the triangular pulses. Since any dis
the signal
R1 and
areY »applied
as indicated
C1 of theatsas’
tooth generator co„ „oi the slope of the output
sawteeth 3d, and may be adjusted as desired.
The sawtooth wave
is applied to a threshold
multi-vibrator dt. The multi-vibrator is of a
known character provided with a bias at ¿il to
control the voltage level to which the multi
vibrator may be triggered from a nrst state of
operation to
second state of operation. The .
values of resistor R2
capacitance C2 control
the duration of the second state of operation,
thereby determining the instant that the multi
vibrator is returned from the second state or op
eration to the iirst state of operation. This op- :
eration results in a substantially rectangular wave
shown at ft2. The rectangular pulse portions of
the wave d2 are further shaped by resistance R4
and capacitance C5. The capacitance C4 acts as
a blocking condenser and is of considerably larger .
value than capacitance C5. The combination R4,
C5 re-shapes the pulse portions of wave ft2 sub
stantially as indicated at lit, the resulting pulses
being of a substantially triangular shape. The
pulses ¿i3 are applied over output connection ¿ld
to the threshold clipper 9 or amplifier 2d, Figs. 1
and 3, as the case may be.
The operation of the circuit of Fig. 5 may be
summarized in connection with the graph of Fig.
6. The pulses @il are shown in one extreme pc
sition of modulation as indicated at ¿l5 while the
opposite extreme position is indicated by a brok-en
line at .416. When the pulse ¿l5 is applied to the
sawtooth generator 3l', it discharges the con
denser Ci to produce a substantially vertical volt
age drop lil, graph lfï. Upon removal of the pulse
45 from control of the generator, the potential
on condenser C1 commences to build up at the
rate indicated at bis under control of the values
of R1 and C1. Each time a signal pulse is ap
plied to the generator Si', a similar operation is
produced 'thereby ge
The rectangular shaped wave ¿l2 produced by
the multi-vibrator
is shown in graph L, the
multi-vibrator being biased for triggering opera
tion according to the voltage level 49, graph K.
The triangular pulses ¿is produced by the re
shaping of rectangular pulses di is shown in
graph M, it being understood that the rectangu
lar pulse operates initially to charge the capaci
tance C5 according to the time constants R4, C5.
The triangular pulses then decay at a similar
rate as controlled mainly by the values of R5 and
C5. The build-up and decay rates may not ‘ce
tortion in the symmetrical relationship of the
leading and trailing edges of the triangular pulses
is likely to 4occur in the lowers regions of the trail
ing edge, such deviation from the symmetrical
will not enter into the translation of the signal
time displacements.
The Shaper i3 may comprise a multi-vibrator
similar to the one shown at ed, Fig. 5, together
with Shaper network Rl, C5. The signal pulses,
in such case, are applied to the multi-vibrator in
the place of sawtooth wave t2.
While I have shown and described the prin
ciples of my invention in connection with speci
ño apparatus, it will be understood that such
apparatus has been shown for purposes of illus
tration only and not as a limitation of the scope
of the invention as set forth in the objects and
appended claim.
I claim:
for time modulated signal
- producing a sawtooth wave, the
,e of the
accordance with the
pulses, generator means
responsive to
application o? energy at a given
voltage level to produce a substantially square
pulse of give-n width. means to apply said saw
tooth voltage to said generator
to effect
‘,:a fduction oi a Sonar-‘e pulse a given time delay
after the occurrence o: the initiating signal pulse,
means to
square pulse into a triangu
odulating pulse whose time posi
„zh a following signal pulse, and
means t combine the demodulation pulses with
the signal pulses to
composite pulses having
peaks representing the signal components of the
signal pulses.
2. In a receiver for time modulated signal
pulses, means for producing a sawtooth wave,
the teeth of which are timed in accordance with
the occurrence of the signal pulses, a multi-vibra
‘ tor, means to apply said sawtooth voltage to said
multi-vibrator, means to bias said multi-vibrator
to respond to said sawtooth wave for change
from one state of operation to a second state of
operation when the sawtooth potential reaches
a given voltage level, the multi-vibrator being ar
ranged to return to its iirst state of operation
after a predetermined period, whereby a sub
stantially square pulse output is obtained, each
square pulse having »a given time delay relation
exactly symmetrical. but by adjustment of R4 and 7x5 ship with respect to the initiating signal pulse,
means to shape each square pulse into a triangu
larly shaped demodulating pulse Whose time posi»
tion overlaps with a following signal pulse, and
means to combine the demodulation pulses with
the signal pulses to form composite pulses having
peaks representing the signal components of the
signal pulses.
with a following signal pulse, means to combine
the demodulation pulses with the signal pulses,
to form composite pulse energy and means to ob
tain the signal components represented by the
peaks of said composite pulse energy.
3. In a receiver for time modulated signal
pulses, means for producing a sawtoth wave, the
The following references are of record in the
-teeth of which are timed in accordance with the 10 ñle of this patent:
occurrence of the signal pulses, a multi-vibrator,
means to apply said sawtooth voltage to said
multi-vibrator, means to bias said multi-vibrator
to respond to said sawtooth wave for change from
Kell ____________ ..-July 18, 1939
one state of operation to a second state of opera 16 2,212,648
Poch ____________ __Aug. 27, 1940
tion when the sawtooth potential reaches a given
Wheeler __________ __Mar. 18, 1941
voltage level, the multi-vibrator being arranged
Herz ____________ -_July 29, 1941
to return to its ñrst state of operation after a
Wheeler ________ __Sept. 9, 1941
predetermined period whereby a substantially
square pulse output is obtained, each square pulse 20 2,270,773
having a given time delay relationship with re
spect to the initiating signal pulse, means to
shape each square pulse into a triangularly shaped
demodulating pulse whose time position overlaps
Reeves ___________ __Dec. 16,
Sonnentag ________ __Jan. 20,
Fredendall ________ _„Dec. 25,
Deloraine ________ __Dec. V24,
Young __________ „_Dec. 24,
Greig ____________ __Feb. 25,
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