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Патент USA US2408064

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Sept. 24, 1946.
' Filed July 29, 1944
2 Sheets-Sheet lA
7D CHA/wa SI"4 fre.
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sep't. 24,1946.l
Filed July 29',4 1944
_2 sheets-Sheet 2
l. a?
Patented Sept. 24, 1946
2,408,063 `
-Donald D. Grieg, Forest Hills, N.> Y., assignor to
Federal Telephone and Radio Corporation,
"N ew York, N. Y., a corporation of Delaware
Application July 29, 1944, Serial’No. 547,123
11 Claims.
(Cl. 179-15)
This invention relates to4 multi-channel com
munication systems and more particularly to the
the undulationshaving relative maximum ampli
tude are segregated by clipping a given portion
of their amplitude which is ampliiied and de
modulated for recovery of the original signal
selective reception of a plurality of ltransmitted
One of the'objects of this invention is to pro 5 conveyed over this channel.
The clipped portions, thus obtained from the
vide anv improved `method and means for the
first peak riding clipper, may also be used to sub
selectivereception in a multi-channel communi
stantially eliminate from: the train of undula
cation or broadcasting system of a plurality of
intelligence conveying channels, the different
channels being distinguishd by different identi
fying characteristics.
tions, before the train of undulations is applied l
to subsequent peak> riding clipper circuits, which.
act to successively segregate by clipping of their
peak portions, the _undulations havingA relative
maximum amplitudes in sequential order accord
A further object Aof the invention is to provide
a method and vmeans at the receiving pointsof
a- communication' system for selectively receiving
any one'or more-of a plurality’of signal channels
ing to their values. In_order to achieve this
effect, the clipped portions of a given channel
or channels having relative -maximum amplitude
undulations, may be iirst inverted and'thenmixed
with the train of undulations from the original
'translator or apreceding channel, whereby the
Another object of the invention is to provide
methods and means for selective multi-channel 20 firsty orv preceding maximum amplitude undula
tions-are substantially cancelled out. This brings
reception, wherein signal intelligence is conveyed
in line for segregation by the peak riding- clippers
over each channel by means of a series of pulses
in the subsequent channel circuits the undula
which are modulated with respect to any one of
tions of the channel having the second or suc
a number of their characteristics such as time
position, for example, in accordance with the 25 ceeding maximum amplitude undulations.
This principle may be employed to successively
instantaneousV value of the intelligence, and
eliminate lone channel after another before ap
wherein the pulses of >the individual channels
plying the train of undulations to the peak riding
have different identifying widths.
clipper of the next channel.
An additional object of the invention includes
The. above and other objects and features of
the provision of a method and means for `the
the invention will become more apparent upon
selective reception of. the respective channels in
consideration of the following, detailed descrip
multi-channel communication systems in accord
tion to be read in connection with the accom
ance with the characteristic pulse Widths-thereof.
panying drawings, in which:
According to certainfeatures' of the invention,
Fig. 1A is a block diagram of a receivingv ter
a number of channels,` conveying signal intelli
minal of a multi-channel communication system
gence by means of a series of pulses, eachy chan
according to my invention;
nel. characterizedby anidentifying pulse width
Fig. 1B is a block diagram of avmodifled form
and the >pulses of which are modulated with re
spectto one of their characteristics in accordance l of thereceivingterminal of Fig. 1A.l
with. the signal intelligence to> be conveyed are 40 Fig. 2 is a schematic circuit diagram ofA a
width-to-amplitude translator and of a peak
received in time-spaced relation as a single train
transmitted in time-,spaced relation over a com
mon transmission medium, such as a transmis
_ sion line or a given carrier radio frequency Wave.
riding clipper circuit of the receiving terminal
ofí‘pulses at the receiving terminal and applied
the incoming pulses, having different widthsifor
circuits of Fig. l; and
Fig. 3 is a graphical illustration of the opera
the various channels, are translatedinto undula
ktions of thecircuits of Fig. 2.
tions ofzsimilar width, the/amplitudes of which
Referring to Fig. 1A, the form of receiving te'r
minal illustrated comprises an Yadjustable pulse
width-to-amplitude translator l, which feeds‘in
parallel the circuits for the first andsecond chan
to a pulse-width-to-amplitude-translator
are made to vary as the-„widths of the corre
spondingpulses. Froml the translator, the undu
lations now characteri'Zed-¿for~ each 'channel byV
an identifying amplitude may then be fed as a 50 nels. The system, of course, may include a num
single'train of undulations-'to a' peak riding clip
ber- of additional channels like the third ,chan
nel shown, each being connected tothe preceding
and peak riding clipper circuits, representing,
channel asshown-between the second and third
channelsz `Theffirst channel includes a peak'rid
the various> channels of Vcommunication respec
tively. >In the, i'lrst‘y peak-ridingV clipper circuit, 55 ing clipper 2,;the' second channel includes a mixer
perfandV to one'or more of aplurality of mixer
3 and a peak-riding clipper 4, and the third
sume, also, that circuit 8 is tuned for a maximum
response, that is for selection of pulse width W1.
In that case, curve c represents the output of
circuit 8 when the circuitis tuned for a maxi
mum response to pulses having the width W1,
illustrating a series of output undulations as ob
tained fromthe different pulse _Widths of curve
channel includes a similar mixer 5 and peak rid
ing clipper 6.
The output of the peak riding
clipper 2 is applied to the mixer 3, mixer 5 receiv
ing the output of mixer 3 and that of the peak
riding clipper 4. The outputs of the peak riding
clippers 2, 4 and 8 may be applied to >democlula
tors, as desired.
a.v In order to clarify this, it may ‘be mentioned
A further channel `Il, which is
at this point, that when the leading> edge of the
pulse W1 is applied at negative polarity, as in
In Fig. 1B, the receiving terminal is made u
' curve b, to circuit 8, an initial undulation 29 is
of the same major circuit elements as the form
j produced, Vwhich is normally followed by undula
not shown, may be similarly supplied from mixer
5 and clipper Ii, as indicated.
tions 38 _and 3|, and so on in the form of a damped
of Fig. 1A, except that in this case, the adjust
able translator I feeds all of thevchannel circuits
wave.r 4 When the. circuit 8 is tuned to a frequency,
the period of which is exactly twice the width
W1, the trailing edge of the W1 pulse occurs where
in parallel, and the output of ther peak riding
clippers 2, «i and 6 are fed into a common con
the initiated, oscillatory energy crosses the zero
nection P, from which the mixers are individually
supplied, the various channel circuits beingA sep
arated by de-couplers D. Further channel cir
cuits, as required, may be similarly connected to
the translator I and the peak riding clipper con
nection P.
axis fromv undulation 29 to the undulation 30.
Since the trailing edge of this pulse shock-excites
the circuit 8 in the same direction at this point,
the undulation 32 produced thereby in circuit 8
adds algebraically to the undulation 30 to produce
a resultantundulation 33. The next succeeding
Fig. 2 illustrates circuit I and 2, as shown in
block form in Figs. 1A and 1B.
The circuit I is utilized for translating a train
of pulses of various widths into undulations hav
ing corresponding amplitude Variations, as de
scribed, for instance, in the copending applica
tion of E. Labin and myself, Serial No. 487,072,
iiled May l5, 1943, wherein the circuit isvdisclosed 30
pairs of undulations produced by the leading and
trailing edges of pulse W1 would normally tend
to produce a negative undulation 34, which would
tend to continue as a damped wave.
tube 9, however, eliminates any such trailing os
cillations so that they do not interfere with the
undulations produced by subsequent pulses ap
as a pulse selector according to pulse width.
plied to circuit 8.
The circuit includes a _limit clipping stagev 'i
as an input coupler, which limits all input pulses
to substantially the same amplitude and, also,
inverts the input pulses from a positive polarity,
as indicated by the pulses of curve a, Fig. 3, to
negative polarity indicated by the pulses of curve
b. The output pulse energy from stage ‘I is ap
A pulse Width less than pulse Vwidth W1, such,
for example, as the width W3 will not produce
undulations as great ras undulation 33, if the cir
cuit tuning is adjusted to correspond to pulse
Width W1’. This is illustrated by undulation 35,
produced in response to the pulse width W3.l The
reason for this is readily apparent, because shock
plied through a resistor R to a tuned shock-ex
excitations, produced by the leading and trailing
citable L.-~C. circuit 8. Connected across the tun
40 edges of the pulses of lesser width than W1, will
able circuit 3 is a vacuum tube 9, the cathode II]
of which is connected to the input side of the
circuit 8, while its anode II is connected to the
opposite side I2 of the tunable circuit. The side
in part be opposed to each other. Undulation 36,
in response to the greater pulse width W2, is like
wise smaller than undulation 33, since here again,
the oscillations, produced in response to the lead
I2 is also connected to a source of anode poten
ing and trailing edges of theA greater pulse width,
tial at I3. The pulse energy, as in curve b, Fig. 3,
from an anode connection I4 of the tube 1 is ap
are in part opposed-to each other, so that the
algebraic summation thereof is less than in the
case of undulations produced in response to pulse
plied to the grid of the tube 9, so as to block con
duction between the cathode Ill and the anode
II, while pulse energy is applied to the circuit 8.
The undulations, which are produced in circuit
Curve c of Fig. 3 therefore represents a series
of output undulations corresponding to the train
8 in response to pulseenergy coming in over con
of pulses, as in curve a, which are present in the
nection I4, are taken 01T through a connection
output connection I5, and which may be- fed to
the peak riding clipper stage 2 and to mixer 3 as
I5 for application to the peak riding clipper stage
2. The undulations in connection I5' arefed
over a condenser I6 to a grid I1 of tube I8." The
inv Fig,` 1A,V or in parallel to all channels as in
rAs the `operating characteristics'of a peak fol
grid circuit includes aresistor I9 and ~a‘biasing
lower or peak-riding clipper are known in the art,
resistor 20, the latter being shunted by the usual
only a brief description of‘such> operation'will
by-pass condenser 2|'. An anode 22, througha
load resistor 23, is connected to the positive end 60 now be given. If, for example, a positive poten
tial, -as represented'by the undulation 33 is ap
24 of an anode potential source B+ at I3. Po
plied to the side'31 of the condenser I6 >(Fig.'2'),
tentials developed across resistor '23 are delivered
grid ' current will flow through resistanceV I9
as output to the next stage at connection 21.
charging' the condenser I6 and resultingV in a
Branching oiî from connection I5 is a connection
2B which serves to feed undulati'ons from the ` negative potential on side 38, thereof. This nega
tive potential is effective on the grid I1, the value
width-to-amplitude translator I to the circuit of
of such potentialbeing proportionate to the volt
channelVv 2 as in Fig. 1A, or to the circuit of chan
age amplitude of the undulation applied to con
nels 2, 3 and others as in Fig. 1B.
denser IS. `The paramentersof the circuit, rep
The operation of the circuits of Fig.v2 will now
be described in connection with the curves of 70 resented lby> condenser I6 and its associated're
sister I9, are such that the resultant time con
Fig. 3.
stant of the circuit will permit the condenser to
Assume for the purpose of ïillustration, the
lose its charge only very slowly and Aonly to a cer
width of the pulses for the'three channels in
curves a and b to be .of the character indicated
tain point. 'I_'he effect of the charge on condenser
I6 is to maintainY a cut-'off bias on the tube I8 at
by the reference characters W1, W2 and W3. As
automatically a peak .clipping levelcorre'sponding
to undulations 35,.which havenow comeltobethe
the level designated by broken liney 39, curve ic,`
Fig. 3.- The charge onthe condenser, ‘represented
maximum amplitude undulationsjinfthe, series
by thisïline 39, willremainvatï this levelfasfa
applied to-clipper'ö.
' È
steady‘state condition,ïsinc_e‘only a` small quan
tity ofthe -charge will be-vdissipated. during -the Ul ' 4In‘ïthe form offthe‘ circuit Iarra'ngementshown
in- Fig.'A flB-,the successive elimination` of ‘the max
intervals between undulations, and! the-'charge
imum amplitude undulations Yoff preceding ' chan
willïbe kept replenished byeach succeeding> un- f
nels iSv-obtained by mixing the originalY series of
dulation. The loss'ofï the charge and'- thereby the'
undulations '(icurvecl- with'îthe cumulative out
cut-off level is, of course,- also a'function of‘the
put off all» the-'preceding peak riding clippersbyl
repetition rateof the-undulations«responsible lfor
feeding» ïthevoutput off these clippers finto-the
the establishment'of» the level; v'It becomesk clear,
common line P, and' deriving therefrom thecom
therefore, that only portion`40 of the-undulation
binedputput> o_f ïthefprecedin'g clippers, as shown
33 appearing above theaforesaid'level‘39 will be> .
for clippers 2 _and 4' in 'curve h. As this combined
passed by the-tube I8, and will appear `in its out
put-atei. The function of such a peak follower
or peak riding 4clipper as at 2, is to tend to-'clip
oilv aiixed amount- from the crest of thoseapplied
output of thepreceding clippers isi mixed with-'the
original undulations (curve c), 4theundulations
undulations having maximum amplitude,- regard
less of the actual amplitude of such undulation.
Iffundulations of lesser amplitude than thatfrep
resented by the level 39 are applied, suchundula
tions would not Ibe represented inthe outputl be
causefof‘the peak clipping'level line 39 which is
clipper 6» receives the remaining undulation-35Lto
tions may be employed to obtainfthe-separationof
established by undulations -having a maximum
the undulations of additionalchannels.
relative amplitudek extending above the level V39,
This circuit tends, therefore, to select maximum
amplitude undulations in each case. 'The level
represented byline 39, as will be now understood,
It will be apparent that by varying the tuning
of the resonant circuit-8 for eiïective `maximum
response to other pulse widths, the sequen-ceeofv
the selection of thev channels may be changedïat
33 and 36 are reduced to negligible size :and the.r
acton. The decouplers D between channels-serve
to Vprevent the feedback of the clipper‘outputt‘o-î
Ward-thepreceding» channels.
varies withthe maximum amplitude of the un
dulations receiv,ed,'so that, if undulation 33 were
wi1l,i-f desired.
l ,
. ItA is thus _seen that by a` combination of? the
circuits'hereinabove described, an‘eiîective pulse
width selector has been provided, vin accordano
eliminated :from the > series ofv undulations ~ shown
in curve'c,the undulations having the next „maxi- ,
mum relativeamplitude, would be thoseïreferred l
with the objects set forth heretobefore.
to'by'reference 36 curve f, and the clipping level
would automatically be established at 4i, accord
ingly. In each case, therefore, the peakV clipping
level will beyestablished automaticallyA to >'select
' ~
' While I have described above the principles of
this> invention Vin connection ’with speciñcap‘
paratus, vit is to be clearly understood that >this
description is made Vonly by Way of example, and
the‘crest of the undulations having a maximum
amplitude for a' given series ofV undulations.
not as a limitation on thek invention vand the
iscope of accompanying claims. ’
This characteristic I make use of by using the
1. A methodl of selectively receiving a plurality
of channels of 'communication from a multi
clipped peaks of themaximum amplitude vundula
Further similar clipping and mixing » ‘opera
tions to successively- eliminate such maximum
undulations whereby the peak riding clipper'cir
`ch‘annelvtrain of pulses wherein the pulses of
cuit in the subsequent channels are enabled to
each channel differ from pulses of otherchannels
select undulations having the-next highest ampli 45 by a diiîerent`> identifying width; comprising
translating said pulses into a series of» corre
tude, in succession.
sponding undulations the amplitudes of ywhich
The clipped peaks, for instance, of undul-ation
33, -ind-icated by curve d, may be amplified and
vary substantially as the respective wid-th ’ofthev
corresponding pulses; andv successively -selecting
inverted in the clipper circuit` 2, to assume the
form as shown in curve e which are then mixed 50 the undulations of each channel in accordance
with .the relative values of'the'amplitudes thereof.
(at ’mixer’3 with the series of‘undulations repre
sented in curve c. The resulting series'of un
2. A method according to claim 1, wherein the
operation of translating includes V_the steps> of
dulations, as obtained from mixer 3, is shown in
curve f where itis seen that the undulations 33
have now practically disappeared, and undula
»tions 36 having assumed lthe role of the maximum
amplitude undulation formerly had by undula
establishing a resonating >condition in accordance
with a desiredgsequence~ offthe' channels tojbe
3. 'A method according to claim l, wherein the
tions 33. It should be noted that since the fre
operation of translating includes the steps of
quency response characteristic is limited to a
producing periodic oscillations by means of said
practical degree, the sharp peaks which result 60 pulses under conditions of resonance at a fre
quency having a period proportionate to the
from this subtraction are considerably reduced in
width of the pulses of a given first channel.
'This train of undulations (curve f) is applied
4. A method according to claim 1, wherein the
to .the peak riding clipper circuit ll, Fig. 1A,
`operation of selecting includes the steps of suc
where, automatically, a clipping level 4l is estab 65 cessively clipping the peaks of the undulations in
lished curve f, and the peaks 42 of the undula
the order of the values of the amplitudes thereof.
tions 36 are clipped off as shown in curve g. This
5. A method of selectively receiving a plurality
output is analogous to that obtained from peak
of channels of communication from a multi
riding clipper 2 for channel I, and may be sim
channel train of pulses wherein the pulses of each
ilarly used to obtain a reproduction of the orig 70 channel diiîer from pulses of other channels by
a different identifying width; comprising trans
inal signal for channel 2 by demodulation. Por
lating said pulses into a series of corresponding
tions 42 may also be used to eliminate undula
undulations the amplitudes of which vary sub
tions 36 by inversion and mixing in mixer 5 with
stantially as, the respective width of the corre
the «output of mixer 3. This enables peak riding
clipper 6 in the circuit of channel 3 to establish 75 sponding pulses; and selecting the undulations
o?‘a> given channel by successive maximum peak
clipping the undulations of the channels having
accordance with thev relative amplitude ‘_thereof.
*9.y A system accordingto »claim 8,_wherein said
the larger amplitudes, employing the resultant of
said maximum peak clipping operationto elimi
means for translating includes _a vresonant cir
cuit tuned to a frequency having a vperiod pro
nate said undulations having ,the larger ampli
portionate to the'width ofv the pulses of a- given
tudes fromithe .said series', and maximumv peak
clippingV the maximum amplitude» vundulations
first channeli
l0. A system for selectively. receiving a plu
rality of channels of communication from-a mul
ti-channel train of-` pulses wherein 'the pulses of
of communication from a multi-channeltrain .of 10 each channel diifer--fromvpulses of other chan
nels by a different'identifying’width; compris
pulses Wherein'the pulses of each channel differ
ing >means for translating said pulses into a series
from pulses of _other channels bya diñerent iden
l ‘6. A method of selectivelyireceiving a 'channel
tifying width; comprising translatingl said» pulses
- of corresponding _undulations .the amplitudes of
into aseries of corresponding'undulations the am
plitudes _of Which varysubstantially as .the re
spective Width ofv the corresponding pulses; .and
selecting the undulations of a given vchannel by
maximum peak clipping the undulations of the
Which vary substantially as the respective Width
of vthe corresponding pulses, including areso
nant Vcircuit tuned to a frequency having a
period proportionate to lthe Width of the pulses
of a given ñrst channel, a plurality of receiving
channels each having circuit means for select
channelshaving the larger amplitudes; invert
ingfamplifying and mixing the resultant of said 20 ing the vundulations of a channel when the un
dulations thereof arev of maximum amplitude,
maximum peak clipping operations with the` said
including peak-rider clipping means inl each-re
series-ofundulations representing all the chan
ceiving channel, and-mixer means-in all but the
nels,> and maximumpeak `clipping the maximum
amplitude undulations thus obtained.
»» - .
first receiving channel; means for applying said
A method-of -selectively receiving ia plural 25 series of undulations to thel circuit means of the
first and second receiving channels; and means
ity; ofchannels _of communication from` a multi
for applying- the output of the circuit means of
channel train’of pulses wherein thepulsesof
each receiving channel to the. mixing means of
each-rchannel'diiîfer from pulses of otherchan
the succeeding receiving channel.
nels by a different identifying width; compris
ll. A system- íor~selectivelyreceiving a plu
ing translating said pulses into a series of corre 30
rality of channelsof communication from a mul
spending undulations of the amplitudes of which
ti-channel train ofA pulses whereinthepulses
vary Isubstantially vas the respective Width of the
of each channel differ-from pulses of other chan
corresponding pulses; andr selecting the undula-l
nels by a different identifying width; compris
tions any-'of said 'channels by successiveY maxi
mumpeak clipping the ¿undulations of the chan 35 ing means for translating said pulses into a series
of corresponding undulations the amplitudes of
nels preceding those of any given channel with re
spect toy their amplitude values; .mixing thatrain
of undulations obtained for the channel immedi
ately preceding any given channel, before said
which vary substantially as the respective width
of Ythe corresponding-pulses, including a reso
nant circuit tuned tov a frequency having a
train has been subjected'to maximum'peak-clip 40 period proportionate to the Width of the pulses
ping,¿ with the inverted-and amplified output of
the maximum peak clipping-operation as. applied
of a givenchannel; a plurality of receiving chan
nels each having circuit means for selecting the
undulations-of a channel Iwhere the undulations
to 'said preceding channel, .and .maximum peak
thereof are of maximum amplitude, including
clipping the series of undulations -thus .i obtained.
8. A multiplex system. forfselectively and si 45 peak rider clipping means in each »receiving
channel, and mixer means in all but the first
multaneously receiving any. of a number .of chan'
channel; means for applying ¿said series of un
nels of communication- froml -aï` multi-channel
dulations to each of said channel circuit Amea'r'is;`
train of-v pulses wherein the pulses of -each _chari-Í
means for receiving the output of the circuit
nel diiler from. pulses ofother channels ibyia dii
Íerent identifying Width; comprisin'gïfm'eans‘i’or
translating saidv pulses,v into a. series.` of , corre.
sponding undulations the amplitude` ’of` which
Vary substantially as the respective width ofthe
corresponding pulses common to all channels;
and for each channel, means for selecting’ from
said series the undulations of a given channel' in
50 means of each of the channels separated into
channel sections; and means for »applying- ‘the
cumulated output of the preceding circuit means'
to the mixer means of a given channel.
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