Патент USA US2537091

Jan. 9, 1951
L. RIEBMAN
2,537,090
SYSTEM FOR MAINTAINING MAXIMUM PULSE
DEFINITION ON HIGH Q, NETWORKS
Filed Aug. 6, 1945
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.ILEON RIEBMAN
Jan. 9, 1951
L. RIEBMAN
2,537,090
SYSTEM FOR MAINTAINING MAXIMUM PULSE
DEFINITION 0N HIGH Q NETWORKS
Filed Aug. 6, 1945
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LEON ' RIEBMAN
Patented Jan. 9, 1951
2,537,t9t
UNITED STATES PATENT" OFFICE
2,537,090‘
SYSTEM‘ FOR MAINTAINING MA-XHWUM
PULSE DEFINITION 0N HIGH Q NET
WORKS
Leon Eiebman, United States Navy
Application August 6, 1945, Serial No. 609,294
5 Claims. (Cl. 178-44)
(Granted under the act of March 3, 1883, as
amended April. 30, 1928; 370' 0. G. 757 )7
1
2
This invention relates- to‘ a method of and a
means‘ for maintaining maximum de?nition of.
electrical‘ impulses where such impulses are to be
merit of the invention in which rectangular pulses
must be passed through a high pass ?lter;
Fig. 1A is a series of waveforms useful in ex“
passed through electrical‘ networks which are
glaining. the operation of the‘ circuit shown in
readily shocked into damped oscillations.
.5 ig. 1;
For‘ various purposes in the art, it is necessary
Figs. 2 and 3 are schematic diagrams of typical
that pulses of electrical! energy be applied to net
modi?cations oi‘ the embodiment shown in Fig. 1;
works having the property that their capacity
Fig. 4' shows an application in a receiver cir
for‘ energy storage is high in relation to the en
cuit in which pulses comprising several cycles of
ergy'whichv they dissipate: i. e. high Q networks. 10 an approximate sine'wave must be passed through
Leading and trailing edges of pulses usually con
a high pass ?lter.
tain high frequency‘ components‘ which tend to
In particular Fig. 1 illustrates an embodiment
shock excite- damped oscillations in such net
of the invention in which a signal comprising rec
works. The oscillations excited by the trailing
tangular pulses must be passed through a high
edges will normally start with a phase which is the 1,5 “Q” high pass ?lter l2. The signi?cant portion‘ of
opposite of that‘ with which those excited by the
the input signal‘ applied at terminal 5 i is shown
leading edges start. Consequently, after the end
at waveform a in Fig. 1A. The leadnig edge of the
of the pulse, damped. oscillations which are the
pulse shock excites damped oscillations in the
sum of those started by the pulse edges will con
?lter network It which appear at the filter output
tinue at the output of the network. When com
20 it as waveform b (shown without regard to time
delay in the high pass ?lter). The trailing edge
of the pulse shock excites damped oscillations
paratively short pulses are applied to a high Q
network, the amplitude of the remaining oscilla
er opposite-initial polarity which‘ appear as wave
tions will depend upon the resonant frequency or
form 0 (also shown without regard to time delay
frequencies of the network and the pulse dura
tion, and can vary from approximately twice the 25 in the high pass ?lter): at terminal is. The two
groups of damped oscillations illustrated in wave
initial amplitude to a negligible value accord
‘forms 2) and 6 respectively combine after the ter
ing to the phase angle at which the two sets of
mination of the pulse to form ,a composite wave
oscillations add. In the general case, however,
form, ‘but for purposes of clarity each group may
these oscillations will impair the pulse de?ni
tion at the output, and their continuance will ‘ he considered separately with regard to their be
havior in the cancellation network.
temporarily render the output circuits ineffective
for subsequent signals. The present invention
provides a method of and means for terminating
such oscillations by cancellation.
The ire
.quen-cies contained in the input pulse are for the
most part vin the attenuation band of the filter
and do not appear at output terminal It. The
cancellation network comprises a resistive chan~
nel it through which the ?lter output is passed
substantially unmodi?ed in parallel with an arti
?cial line channel It in which the ?lter l 2 output
is attenuated and delayed one half period or any
Cancellation
is effected‘ after a ?xed period of time through the
use of circuit elements designed for that pur
pose. It will be apparent from the following de
scription that, because of the timing relationships
inherent .in the operation of the invention, an ex
40 suitable odd number of one half periods if de—
act reproduction of the input pulse is not rendered
sired. The line it is driven and terminated by a
directly available. However, the output wave
pair of resistors, it and It, which in combination
forms are such that, either they are intelligible
with the-series, resistive element l5 form a pi type
to those skilled in the operation of equipments
network. To prevent the occurrence of re?ec
with which the invention is used, or they lend 45 tions in- line l8 resistors M and It are made equal
themselves to modi?cation in circuits knownv to
to the characteristic impedance of the line.
the art so that they canbe interpreted. More
When signals passing through the two channels
over, the output circuits will ,be returned to ei
are recombined at ll, all except the ?rst half
viective operation in a minimum time.
cycle (due to the half cycle delay introduced by
Other objects and features of the present in
line E8) of each group of ringing-oscillations will
vention will become apparent upona vcareful con
be cancelled. Consequently, the output at El will
sideration of the following detailed description
appear substantially as shown by waveform d, i. e.,
when taken together with the accompanying
as two displaced half cycles of opposite polarity
drawings:
.
whose displacement is a function of pulse width
Fig. lislaschematic diagram of one embodi
55
and theperiodrof the dam-Perl Oscillations After
3
2,537,090
4
the second half cycle, the circuit is receptive to
factured and used by or for the Government of
subsequent pulses.
the United States of America for governmental
purposes without the payment of any royalties
Waveform d contains indications of the pulse
width which can be interpreted by a skilled op
erator from a suitable presentation on a cathode
ray oscilloscope, for example. Accordingly, the
output waveform d is applied to a full wave rec
CM
thereon or therefor.
What is claimed is:
1. In electrical networks through which elec
trical impulses are to be passed and which are
readily shocked into damped oscillations in re
sponse to the application of such impulses, a
pulse length is thus de?ned by the leading edges 10 method of maintaining maximum pulse de?ni
tion, which comprises, dividing the damped
of the adjacent half waves.
ti?er IS, the output of which appears on cathode
ray oscilloscope 29 as shown in waveform e. The
oscillations which result from the application
Fig. 2 illustrates a modi?cation of the embodi
of an impulse to a network into two identical
ment shown in Fig. 1, In this modi?cation the
groups, subjecting one of said groups to an in
delay line 28 is terminated in a short circuit 26,
terval of delay determined by the frequency of
so as to not only delay the output from the high
the damped oscillations, attenuating said one of
pass ?lter 22 the desired amount but to re?ect it
said groups to an extent determined by the decay
back to terminal 23 with a phase reversal. These
factor of the damped oscillations recombining
re?ections will then combine with the original
said one of said groups with the other of said
output at terminal 23. Thus since the re?ections
appearing at terminal 23 are phase reversed the 20 groups, said interval of delay being such that
complete cancellation of the recombined oscilla
delay provided by line 28 should equal an even
integral number of one-half periods for proper
cancellation of damped oscillations.
Fig. 3 illustrates a second modi?cation of the
embodiment in Fig. 1. If a plurality of ringing
frequencies are excited in the high pass ?lter 32,
a second ?lter network 33 is used in place of a
delay line. Filter network 38 is designed to have
its cut-off frequency in the region of the ringing
frequencies in order that each such frequency
will experience a 180 degree phase shift. This
?lter like lines l8 and 28 in Figs. 1 and 2 must
also be designed to have attenuation properties
such that upon recombination at terminal 31 each
frequency will approach cancellation after the
time delay introduced by the ?lter 38. The out
put waveform will again provide the basic de?
nition of pulse width. In other words the at
tenuation property of lines 18 and 28 as well as
?lter 33 is a function of the delay introduced by
the delay networks and the decay factor of the
damped oscillations applied thereto.
Fig. 4 illustrates another embodiment of this
invention in which the input signal at terminal
tions result, and determining the impulse dura
tion by measuring the time separation between
the remaining oscillations of the respective
25 groups.
2. In electrical networks through which elec
trical impulses are to be passed and which are
readily shocked into damped oscillations in re
sponse to the application of such impulses, a
30 method of maintaining maximum pulse de?ni
tion, which corn-prises dividing the damned oscil
lations which result from the application of an =.
impulse to a network into two identical groups,
subjecting one of said groups to an odd integral
35 number of one-half periods of delay, attenuating
said one of said groups to an extent determined
by the decay factor of the damped oscillations,
recombining said one of said groups with the
other of said groups whereby complete cancella
40 tion of the recombined oscillations result, and
determining tbeimpulse duration by measuring
the time separation between the remaining oscil
lations of the respective groups.
3. In electrical networks through which elec
4| is a pulse comprising several cycles of an ap iii trical impulses are to be passed and which are
readily shocked into damped. oscillations in re
proximate sine wave as shown by the oscillogram
sponse to the application of such impulses, a
f. The high pass ?lter 42 will pass the signal
means for maintaining maximum pulse de?nition
frequency and is excited into damped oscillations
comprising, a pi type electrical network having
by the wave shape of this signal. The damped
one series and two shunt legs, said pi network
oscillations are cancelled at terminal 41 substan
connected at one end to the network in which
tially as before. A low pass ?lter 8 is used in
damped oscillations are excited, the other end
the channel in which the damped oscillations
of’ said pi network forming an output terminal,
are attenuated, delayed, and phase shifted. This
a delay means connected between the shunt legs
?lter passes the damped oscillations, but is so
designed that the original input signal is in its r‘ of said pi network, said delay means acting to
attenuation band. Consequently, the original
input signal frequency is not cancelled at ter
minal 41, but the damped oscillations are.
delay the damped oscillations applied thereto by
an amount equal to an odd integral of one-half
periods, said delay means also acting to attenuate
It is apparent that for use with this invention
the oscillations applied thereto._
the high and low pass ?lters must be designed 60
4. In electrical networks through which elecso that the frequencies applied will be shifted
trical impulses are to be passed and which are
readily shocked into damped oscillations in re
180 degrees in phase and so that the attenuation
requirements of the frequency or frequencies
sponse to the application of such impulses, a
means for maintaining maximum pulse de?nition
present will be met. High pass ?lters are used
comprising, an impedance element having input
when the required attenuation decreases with
increasing frequency; low pass ?lters are used
and output terminals, the input terminal of said
when the opposite requirement exists.
Although I have shown and described only
impedance element being connected to the net
work in which damped oscillations are excited,
and an arti?cial transmission line connected in
certain and speci?c embodiments of the inven
tion it is to be understood that I am fully aware 70 shunt with said impedance element, said line
of the many modi?cations possible thereof.
short circuited at one end to provide re?ection
with inversion, said line acting to delay, invert
Therefore this invention is not to be restricted
except insofar as is necessitated by theprior art
and attenuate the damped oscillations applied
and the spirit of the appended claims.
thereto, said delay interval being equal to an
The invention described herein may be manu 75 even integral number of one half periods.
2,537,090
5. In electrical networks through which elec
REFERENCES CITED
trical impulses are to be passed and which are
The
following
references are of record in the
readily shocked into damped oscillations in re
?le of this patent:
sponse to the application of such impulses, a
UNITED STATES PATENTS
means for maintaining maximum pulse de?ni
tion comprising, a pi type electrical network hav 5 Number
Name
Date
ing one series resistive leg and two shunt resistive
2,144,812Rieber __________ __ Jan. 24, 1939
legs, said pi network connected at one end to
2,236,134
Gloess __________ __ Mar. 25, 1941
the network in which damped oscillations are
2,310,692
Hansell ___________ __ Feb. 9, 1943
excited, the other end of said pi network forming 10 2,377,903
Rieber __________ __ June 12, 1945
an output terminal, a ?lter circuit connected
2,386,088
Bingley et a1 _______ __ Oct. 2, 1945
between the shunt legs of said pi network, said
2,410,233
Percival __________ __ Oct. 29, 1946
?lter circuit arranged to provide a 180 degrees
phase shift of the damped oscillations applied
thereto, said ?lter network also arranged to at 15
tenuate damped oscillations applied thereto.
LEON RIEBMAN.
_