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Патент USA US2406882

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Sept. 3, 1946.
Filed Dec. 15, 1942
. /'34 H4753
IVO/PMFIN h’. you/v6, JR.
BY my
Patented Sept. 3, 1946
Norman H. Young, Jr., Jackson Heights, N. Y.,
assignor to Federal Telephone and Radio Cor
poration, Newark, N. J ., a. corporation of Dela
Application December 15, 1942, Serial No. 469,044
6 Claims. (Cl. 178-44)
This invention relates to radio impulse sys
tems and more particularly to systems for se
lectively ?ltering pulse modulated waves in
accordance with the amplitude of the pulses.
In the copending application of D. Grieg en
titled “Receiver system,” Serial No. 467,516, ?led
December 1, 1942, methods and means are dis
closed for selectively ?ltering a wave modulated
wanted pulses with substantially a complete
elimination of unwanted pulses.
For a further understanding of the invention
reference may be had to the following detailed
description to be read in connection with the
accompanying drawing, in which:
Fig. l is a schematic illustration of a circuit
in accordance with my invention, and
with pulses differing in amplitude so as to elimi
Fig. 2 is a graphical illustration showing the
nate unwanted pulses whether or not they are 10
reduction and eliminating features of the
of less or greater amplitude than wanted pulses.
It is an object of my invention to provide an
Referring to Fig. 1, the pulse reducing and
additional method and means for accomplish
eliminating system of my invention comprises
ing the same result.
Another object of my invention is to provide 15 an ampli?er circuit ID, a ?lter l2‘ and a clipper
IS. The ampli?er circuit may comprise any ar
a method and means for amplifying a pulse
rangement of elements whereby an input-output
modulated wave to reduce the amplitude of the
characteristic is established so that an increase
pulses greater than a given amplitude.
of input potential causes the output to increase
The reduction in amplitude or the elimination
of the pulses of amplitude greater than a given 20 to maximum and then to decrease toward zero.
Such a. characteristic is illustrated at IS in Fig. 2.
amplitude such as the amplitude of a Wanted
For purposes of illustration, I have shown in
pulse is accomplished in accordance with my in
Fig. 1 an ampli?er circuit comprising an input
vention by applying the pulse modulated wave to
vacuum tube l6 having zero bias and two ampli
an ampli?er having an input-output charac
?er tubes 2| and 22 the grids 23 and 24 of which
teristic such that an increase of input potential
are connected to the anode I1 and the cathode
causes the output thereof to increase to a max
l8 of the tube IS in push-pull arrangement. The
imum and then to decrease toward zero. The
anode I ‘l is provided with a positive bias through
gain of the ampli?er may be adjusted so that
a resistor I 9, and is connected to the grid 23
the peak of the wanted pulse lies near the max
a coupling condenser 2'5. The grid 23 is
imum of the input~output characteristic so that 30
with a negative bias C1 through a re-_
the wanted pulse is ampli?ed a desired value
sister 21. The cathode l8 of the tube I6 is con
and the pulses of greater amplitude are distorted.
nected through a resistor 28 to ground. The
The distortion produces sharp pulse portions de
cathode I8 is also connected to the grid 24
?ning the leading and trailing edges of the
through a coupling condenser 29. The grid 24
larger pulses according to the amounts they
is biased negatively by a potential C2 through
extend beyond the maximum of the ampli?er
a resistor 30. The cathodes of the tubes 2| and 22
input-output characteristic. These sharp pulse
connected together and grounded at 32. The
portions are limited in amplitude by the max
anodes or plates of the tubes 21 and 22 are con
imum of the input-output characteristic of the
ampli?er. The amplitude of the sharp portions 4.0 nected together to provide an outlet 33, the
latter being connected to a positive potential
may be reduced further by passing the output
through a resistor 34.
of the ampli?er through a ?lter to eliminate the
The input tube l6 operates to apply the input
higher harmonics. This reduces the amplitude
pulse or potential to tube 22 without inversion
of the sharper pulse portions with respect to the
of polarity and simultaneously to apply the in
amplitude of the wanted pulse which, of course,
put potential to tube 2| with inverted polarity.
is of greater duration than the durat’on of the
In the absence of an input potential, the tube
sharp pulse portions. By proper adjustment of
2| is biased beyond plate cut-oil‘ while the tube
the gain of the ampli?er and the proper ?lter
22 is biased to a value permitting a normal plate
ing of the output thereof, an output will be ob
tained in which the wanted pulses have greater 50 current. As the grid Id of tube 16 is made in
creasingly negative by an increasing input po
amplitude than the unwanted pulses. By clip
tential, the grid 24 of tube 22 is made more and
ping this pulse output at a level beyond the max
more negative thereby resulting in a reduction
imum amplitude of the unwanted pulses, a pulse
of its plate current. This causes a rising po
wave will be obtained containing the pulse
tential to occur at the plate output connection
energy according to the occurrence of the
5:5 33 as indicated between points 40 and 4| on the
curve I5 of Fig. 2.
At point 4|, tube 22 is at
plate current cut-off. During the interval be
tween All and M the Voltage on the grid 23 of
greater than the pulse 5|, does not extend through
the decreasing portion between the maximum 4|
and the zero point 42 of the characteristic curve
I5. The output for the pulse 53 is shown at 53a.
tube 2! increases in a positive direction, but
The leading edge of the pulse 53 provides a lead
since bias C1 is so chosen to cause the tube 2| to Cl ing edge 60 for the pulse 530. which extends to
remain at cut-off, the tube contributes nothing
the level a. Since the input pulse 53 extends
to this part of the curve. However, the instant
above the maximum level a the tube 22 takes
tube 22 reaches cut-off, the grid potential of
over and provides a decreasing or trailing edge
tube 2‘! begins to rise above cut-off. As the
6| until the top level b of the pulse 53 is reached.
amplitude of the input potential continues to
rise, the grid 23 of tube 2| becomes more and
more positive and the tube conducts more and
more current causing the potential ‘at the plate
connection 33 to decrease ‘as indicatedbetween
4| and 42 on the curve l5.
At point 42 the in- ‘
put potential has reached a value sufficient to
cause cut-oil’ of the tube l6 and any further in
crease in potential on the grid H! of the tube l6
results in no further change in potential at 33.
While I have shown the increasing and decreas
ing portions of thecharacteristic curve l5 to have
substantially the ‘same ‘slope .in the inverse di
rection, it will ‘be understood that the charac
teristics of the tubes may be such as'to provide
This provides a sharp pulse portion overlying
the leading edge 60., When the trailing edge of.
the input pulse 53 decreases the potential input
applied to theampli?er, a return through the
‘characteristic curve is obtained whereby a sec
ond sharp pulse portion 54 is formed de?ning the
trailing edgeof the output pulse 53a. The pulse
53 is thus distorted by the portion thereof ex
tending beyond the maximum 4| of the charac
teristic curve l5.
‘The‘pulse 54 of amplitude less than the wanted
pulse 5| provides‘an ‘output which in accordance
‘with the adjustment of the ‘ampli?enmay be
smaller as indicated at 55a than the input pulse
entirely different slopes andui?e'ent maximum
As shown in Fig. '2, the pulse portions 52a, 52b,
and minimum ipoints KM and M1, 42' respectively,
53 and 54 de?ning the leading and trailing edges
for the curve. The main feature‘ of the invention,
of the larger input "pulses-52 and *53 respectively,
however, is 'to‘prov'ide the input. and output char
are sharper pulses than ‘the pulse 'output'SIa
acteristic curve with a maximum point whereby
of the wanted'pulse {5L By suitably ?ltering
pulses applied to the ampli?er extending in am '30
the higher harmonics, the ‘sharp pulse por
plitude beyond the maximum point of the curve
tions 52a, 52b, 63 and '64 are ‘reduced in ampli
are distorted and limited in "amplitude.
tude as indicated by ‘the wave 110. ‘By clipping
Assume that the'input to the grid M of the
the wave 10 along a level ‘II preferably ‘above the
‘tube H3 ‘is a .modul‘ated wave ‘having a series of
greatest amplitude of the unwanted pulses, a
pulses i'5l, 52, '53 vand 54,*with the pulse 5| re- ' ‘
‘?nal output wave 80 is ‘obtained ‘having pulse
'peated as indicated. The wave, of ‘course, ‘may
energy 8| which correspond to the pulses 5|.
contain other pulses which occur at random ‘or
the interfering 'pulses 52, 53 and 54 are
vata ‘given frequency ‘not shown with the “group
effectively eliminated. The output‘pulse energy
illustrated in Fig. -2. "The pulses illustrated, how
8| may, of course, be sharpened or otherwise
ever, are ‘representative in ‘that the pulse 5| is
treated as may be desired depending on the use
the wanted pulse while the ‘pulses-‘52, ‘53 and 54
intended for‘the pulse energy thus obtained.
are the unwanted pulses. The 'pulses '52 and
While I have described the principles of my
'53 ‘are ‘of greater amplitude than ‘the 'wanted
invention in connection with a speci?c system,
fpulse while the pulse ‘54 is "of less amplitude.
it ‘will be ‘understood that the system herein
‘To eliminate the unwanted pulses, the gain of
anddescribed is not to be considered as a
the ampli?er TH) “is adjusted so ‘that'the ampli
limitation on'the scope of my invention as set
tude ‘of the wanted'pulse ‘5| is brought near and
forth in the'objects thereof and in the appended
preferably slightly under the maximumpointv 4|
of the input-output characteristic of the ‘ampli
?er. The output ‘pulse 51a ‘is ‘thereby produced 50 I claim:
1. A method of eliminating from a wave modu
in substantially'the same shape‘ as the input pulse
lated ‘with substantially unidirectional pulses of
"5|. The vpulse‘52, however, is greatly distorted
diirerent amplitude and of appreciable duration
since it extends beyond 'the ‘maximum point 4|
thosepulses of greater and'lesser amplitude than
and-‘in ‘fact beyond‘the 'tzero point 42 of the
a wanted pulse comprising distorting the pulses
curve. ‘When this ‘pulse is applied ‘to ‘the ampli~ :
of greater amplitude by producing sharp pulse
her, the tube 2| vpasses the ‘pulse potential ‘up
having high harmonic content from the
‘to the maximum level as ‘indicated at'=a'"thereby
leading and trailing edges of the pulses of greater
producing a leading 'edge'55. Then the tube 22
‘amplitude while leaving the wanted pulse sub
takes over for the potential of ‘the pulse above
the level a thereby providing "a'return trailing 60 stantially unchanged in form, ?ltering said waves
to eliminate the higher'harmonics of the pulses
edge 55‘ to zero. The decreasing potential on the
thereby reducing'theamplitudes of the distorted
trailing sides ‘of the pulse-52 provides a second
pulses with respect'to the amplitude of the wanted
sharp pulse ‘from zero aSJin'dicated by'the lead
and clipping the output pulses at a level
ing edge‘ 51 which extends to'the level a'for the
maximum output ‘amplitude of the un
maximumpoint ‘'4 | . The’ tube'Z I "then takes over
wanted pulses.
for ithe‘remainin‘g decrease in potential below
2. A method. of eliminating from the wave
the ‘level a thereby providing ‘a'trailing edge 58.
with pulses of different amplitude
Thus, the distorted pulse output ‘for the large
and of appreciable duration those pulses of greater
input pulse 52 provides a sharp pulse 52a which
and lesser amplitude than ‘a wanted pulse com
de?nesitheileadin'g edge ‘of the'input pulse 52
prising applying the wave to an ampli?er having
and ‘a second ‘sharp pulse 521) which de?nes ‘the
an input-output characteristic in which an in
trailing ‘edge "thereof. ‘The "amplitudes of the
crease ‘cf input potential‘ causes the output to'in
pulses 52a and ‘52b are limited by'the maximum
crease to maximum‘and then toldecrease toward
point 4| of the characteristic curve ‘l5.
zero, adjusting the gain vof the {amplifier so .that
“The third input pulse 53,'while of amplitude ‘
the peak of the wanted pulse lies near the maxi
mum of said characteristic so that the wanted
pulse is ampli?ed a desired amount without sub
push-pull arrangement, one of the tubes provid
ing an input-output characteristic extending from
, stantial distortion and the pulses of greater
providing an input-output characteristic extend
ing from said maximum to zero.
5. The system de?ned in claim 3 wherein the
amplitude are distorted resulting in sharp pulse
portions having high harmonic content and de
?ning the leading and trailing edges thereof ac
zero to a maximum and the other of said tubes
ampli?er comprises a circuit having a pair of
tubes connected in push-pull arrangement and a
maximum, ?ltering the pulses to eliminate the
third tube to- control the input potential on said
higher harmonics thereby reducing the ampli~ 10 tubes so as to produce an input-output character
tudes of the distorted pulses with respect to the
istic extending from a minimum value to a maxi
amplitude of the wanted pulse, and clipping the
mum value and then from said maximum value
output pulses at a level above the maximum out
toward said minimum value.
put amplitude of the unwanted pulses.
6. A method of eliminating from a wave modu
3. A system for selecting a wanted pulse of 15 lated with substantially unidirectional pulses of
cording to the amounts they extend beyond said
appreciablecduration from a wave modulated with '7
pulses of di?erent amplitude having pulses of
greater and lesser amplitude than a wanted pulse
comprising an ampli?er to distort the pulses of
greater amplitude than the wanted pulse, the dis
tortion producing sharp pulse portions of high
harmonic content de?ning the leading and trail
ing edges of the pulses of greater amplitude,
means to ?lter the pulses to eliminate the higher
harmonics and thereby reduce the amplitudes of
the distorted pulses with respect to the amplitude
of said Wanted pulse, and means to clip the out
put pulses at a level above the maximum output
amplitude of the unwanted pulses.
4. The system de?ned in claim 3 wherein the 30
ampli?er comprises a pair of tubes connected in
di?erent amplitude having a predetermined
fundamental frequency content, those pulses hav
ing amplitude greater or lesser than a predeter
mined level, comprising distorting pulses above a
given amplitude thereby producing sharp pulse
portions and relatively increasing the harmonic
content in varying degree, from the leading and
trailing edges of the pulses above the given ampli
tude, ?ltering said waves to eliminate the higher
harmonics of the pulses thereby reducing the
amplitude of the distorted pulses substantially
proportionally to their harmonic content, and
clipping the output pulses at a level above that
of the greater amplitude pulses after reduction.
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