close

Вход

Забыли?

вход по аккаунту

?

Патент USA US3056900

код для вставки
Oct- 2, 1962
s. 1.. sTooPs ETAL
3,056,890
KEYED INTEGRATE AND DUMP FILTER HAVING CRYSTAL AS INTEGRATOR
Filed June 25, 1959
Fig. 7
Fig- 2
POSITIVE
f0
FEEDBACK
CRYSTAL
K2
ISOQOUTPUT
NEGATIVE
FEEDBACK
‘P6
Fig. 4
CRYSTAL
-l'NPUT
'
POSITIVE
'
FEEDBACKJ
NEGATIVE /
-
Fl 9- 5
1
FEEDBACK
INVENTORS
JOHN E. BENNETT
SHERMAN L. STOOPS
BYJ
_
W {(0%
A TTORNEY
United States “atent Q
we
2
1
3 056 890
KEYED INTEGRATE’ANb DUMP FILTER HAV
ING CRYSTAL AS INTEGRATOR
Sherman L. Stoops, Hamburg, and John E. Bennett, Ken
more, N.Y., assiguors to Sylvania Electric Products
Inc., a corporation of Delaware
Filed June 23, 1959, Ser. No. 822,362
7 Claims. (Cl. 307—88.5)
3,056,890
Patented Oct. 2, 1962 ‘
eluding a high Q energy storage element and means for
rapidly removing the energy stored in the element.
Another object of this invention is to provide a keyed
?lter Which aifords a substantial reduction in space and
weight over electro-mechanical ?lters.
Still another object of the invention is to provide a
narrow band ?lter for a pulse type communication em
ploying a high Q storage element wherein the energy
stored in the element is rapidly removed at the end of
This invention relates in general to communication sys 10 each information bit by gated inverse ‘feedback applied
tems and in particular to a narrow band ?lter for use in
to the storage element.
Brie?y, the ?lter in accordance with the invention em
ploys a crystal, such as a Rochelle salt crystal, as the
the invention is concerned with a so-called “integrate-and
energy storage element for integrating the incoming sig
dump” ?lter for obtaining maximum intelligence from
15 nal. Energy is removed (“dumped”) from the crystal by
the transmission in a pulse type communication system.
means of a negative feedback path which is‘ switched
Heretofore, in ?lters of the type here under considera
into the circuit at the termination of the information bit.
tion, an electro-mechanical resonator with associated am
With quenching initiated at the termination of the input
pli?ers and keying circuitry has been employed as an
pulse, the input signal during the quench period is insig
integrate-and-dump circuit in similar communication sys
ni?cant with respect to the negative feedback signal, and
tems. These resonators generally comprise a magneto
consequently it becomes unnecessry to switch out the
/ strictive rod, made of nickel or other suitable magneto
input signal during this period. The circuitry associated
strictive material, the length of which is varied until it is
with the crystal is entirely transistorized, contributing to
resonant at the frequency of the tone to be detected. The
a substantial saving in weight and volume, and additionally
rod is supported at its nodal point by a disc and the input
signal is applied to a driving coil mounted about one end 25 reducing the requirement for power to operate the circuit.
The system is relatively insensitive to temperature, but
of the rod. An output coil is mounted about the rod at
even if an application should require maintenance of a
the other end, the entire assembly being mounted in a
particular temperature, the oven necessary for doing so is
suitable container, usually cylindrical.
much smaller than that required for the electro-mechani
‘From this brief description of electro-mechanical ?l
cal ?lters of the prior art.
ters, it will be readily apparent that they are relatively
Other features, objects and advantages of this inven
complex and expensive construction. Due to the basic
pulse type communication systems. More particularly,
nature of the construction, the resonator has a very lim
ited frequency range, thus limiting the applicability of
the ?lter. Moreover, since the resonant frequency of
tion will become apparent from the following description
taken in conjunction with the acuompanying drawings, in
which:
'
FIG. 1 illustrate-s a plurality of square wave intelligence
the resonator is dependent upon the dimensions of the
carrying pulses;
magnetostrictive rod it is necessary, in order to maintain
FIG. 2 illustrates the response characteristic of a high
the frequency of the ?lter, to place the resonator in an
Q crystal;
oven to hold the temperature of the assembly at a prede
FIG‘. 3 illustrates the ‘output of the ?lter system when
termined temperature. A commercially available reso
nator of this type of which applicants are aware occupies 40 the crystal is compensated to effect rapid removal of en
ergy therefrom;
a volume of 18 cubic inches, excluding the ampli?er tubes
FIG. 4 is a block diagram of the ?lter circuit accord
and other circuitry associated with the resonator. To func
ing to the present invention; and
tion as a keyed ?lter, in addition to the resonator three
FIG. 5 is a schematic circuit diagram of a preferred ?l
twin triodes and a pentode output amplifier are required.
Thus it is seen that this system of the prior art in addi 45 ter system in accordance with the invention.
With reference to FIG. 1, let it be assumed for ex
tion to being expensive, is bulky and heavy and requires
planatory purposes that a square wave signal carries in—,
considerable power for its operation. More important,
telligence in a communication system. For example, this
however, is the system’s inability to rapidly remove stored
might be a series of pulses, respectively of duration 11,
energy from the resonator, this characteristic precluding
its use in communication systems employing high repeti 50 t2, etc., which is formed from an RF carrier modulated
so as to contain intelligence. To detect this intelligence
tion rate. It has been observed that approximately one
requires that the incoming signal be integrated over the
millisecond is required to remove undesired energy from
period of each successive pulse in a manner that the
the resonator, and since the “dump” period does not con
tribute to the detection of intelligence on the input signal, 55 stored energy from one pulse does not deleteriously effect
the detection of the next successive pulse. This may be
it is apparent that the ?lter limits the amount of intelli
accomplished by a narrow band resonator or ?lter of
gence that can be detected in a given period of time. For
high Q, such as a crystal of Rochelle salt.
example, if a pulse repetition rate of 500 cycles is used,
If energy in the form of a sine wave is applied to a
2 milliseconds would be available for each bit of informa
tion; if one millisecond is required to “dump” the energy 60 narrow band ?lter, such as a crystal, the energy passes
through the ?lter at an increasing exponential rate; i.e.,
of the resonator between information bits, then only one
the frequency response of a high Q resonator follows an
millisecond is available for the build up of energy in
exponential curve of the form: y=A(1——e"at) where a
the resonator, this being the period during which detec
is the time constant, t is time and A is the maximum
tion occurs.
It is an object of this invention to provide a ?lter in 65 amplitude of oscillation at the resonant frequency.
3,056,890
3
4
Should the sine Wave input signal suddenly be removed,
which may be a Rochelle salt crystal. The capacitance
of the crystal and its holder, and such stray capacitance
there will continue to be an output from the crystal which
decreases in accordance with the same exponential func
tion. The length of time of rise and fall are equal, and
both are a function of the quality of the crystal. If,
is there may be in the circuit, is compensated by a neu
tralizing capacitor 26 connected between the output ter
minal of the crystal and the emitter of transistor T1.
The equivalent circuit of the crystal and its mount be
ing essentially a series circuit comprising inductance, ca
pacitance and resistance, the crystal integrates the am
however, radio frequency energy is applied to the crystal
as a short pulse, for example of duration 11, which is
short compared to the total exponential rise time, the
rise envelope is almost linear in the initial portion, and
exhibits a normal exponential decay after removal of the
input pulse, as shown in FIG. 2. As was noted earlier,
the intelligence to be detected is contained in the pulse
pli?ed input signal in the manner described above,_ the
integrated output being applied to the base of transistor
T .
zTransistors T2, T3, T4 and T5 and their associated cir
cuitry constitute highly degenerated ampli?er stages hav
itself, namely, during the period t1 in FIG. 2, with the
decay period contributing nothing to the detection. It
ing substantially constant gain, and except for the stage
is therefore apparent that considerably more information 15 including transistor T5, have substantially constant phase
could be detected in a given time if the ‘output of the
relationship. The ?nal stage of ampli?cation (T5) in
crystal were terminated at the tnstant, of termination of
cludes a tuned circuit in its collector circuit including the
the input pulse. In other words, if the energy stored in
parallel combination of capacitor 28, resistor 30 and in
the crystal at the termination of the'period t1 couldbe
ductance 32 which contributes to the gain of the stage,
removed instantaneously, the crystal would then be ready 20 and eliminates any tendency for high frequency oscilla
to detect the next pulse substantially immediately follow
tions. By appropriate selection of the elements of the
ing the termination of the preceding pulse; Stated still
tuned circuit a certain amount of phase correction may
another way, with rapid removal of the energy stored in
be introduced without appreciable sacri?ce of gain of the
the crystal, the repetition rate of the input pulses can be
stage. By reason of the ?ve stages of application (or any
increased while maintaining the detection e?‘iciency of the 25 other ‘odd number) the output signal appearing at the
crystal. The desired response is shown in FIG. 3, being
collector of transistor T5 has a phase angle of 180° rela
tive to the input signal. The circuit thus far described,
therefore, would prouce at output terminal 14 signals cor
responding to that shown in FIG. 2 (exponential rise and
triangular in shape instead of exponential, due to integra
tion over only the initial portion of the exponential char
acteristic and rapid removal of the stored energy at the
termination of the input pulse.
Referring now to FIG. 4, the characteristic shown in
30
exponential decay) for each input pulse of radio frequené
cy energy.
FIG. 3 is obtained, according to the present invention,
As has been pointed out hereinabove, an important
by applying the input signal across a crystal 10, such as
aspect of the present invention is the rapid removal of
Rochelle salt, a high Q device, ‘which integrates the sig
energy from the crystal 10 at the termination of each
nal for a predetermined period of time, approximately 35 input pulse. To this end, at an appropriate time tran
the duration of the input pulse. The output of the crystal
sistor T6, the base of which is connected through ca
10 is ampli?ed in a highly degenerated ampli?er 12 hav
pacitor 34 to output terminal 14, is gated on by a suit
ing constant gain and phase relationship, the output at
able pulse applied to the base of the transistor. Filters
terminal 14 being 180° out of phase relative to the input.
of the keyed type being primarily useful in synchronous
At the appropriate time during the exponential rise por
systems where the beginning and end of each informa
tion of the response, the output appearing at terminal 14
tion bit is known, a timing pulse generated at the end
is fed back through a gate circuit, shown diagrammatical
of each information bit may be employed to trigger a
ly as a switch 16, to the input to the crystal. This nega
tive feedback signal rapidly reverses the build up and re
moves the stored energy from the crystal in a very short
suitable gate pulse generator. For example, the gating
pulse may be derived from a monostable circuit and
applied to terminal 36. Since any gating circuit which
time. The system gain of ampli?er 12 is substantially 45 opens to class A operation will have transients, it is
greater than the minimum desired dynamic range of the
necessary to insure that the spectral energy of these
?lter, and accordingly the input to the crystal need not
transients lies outside the pass band of the system. To
be removed during the “dump” period of the crystal.
this end, the normally rectangular pulse from a mono
When all of the energy is removed from the crystal 10, the
stable circuit, which contains high frequency components,
gate or switch 16 is opened, opening the negative feed 50 is modi?ed or shaped to remove the high frequency com
back path, to permit integration of the next succeeding
ponents prior to its application to the transistor. As
pulse.
In some applications of the system it may be necessary
shown, the pulse is double integrated by resistor 38,
capacitor 40 and resistor 42 and coupling capacitor 34'
to apply positive feedback to the crystal to insure a linear
55 to provide a rounded pulse, the rate of change in ampli
initial buildup. For example, since the function
tude of which is gradual throughout, for application to
the base of transistor T6. The spectral energy of a pulse
of this shape, termed a “soft gate” hereinafter in the
is. linear only up to about one-tenth the 63% point, when
low repetition rates are employed it may be necessary to
alter the response of the crystal to maintain a linear char
acteristic throughout the integration period. In general,
then, when the crystal buildup time is less than ten times
the integration time, positive feedback is necessary. The
positive feedback, when used, is applied over connection
speci?cation and claims, is signi?cantly below the lowest
frequency crystal contemplated for use in the present
?lter application. Thus, the use of the “soft gate” allows
the system an unlimited upper frequency as far as inter
fering transients from the gate ‘are concerned.
When transistor T6 is rendered conducting by the gat
20, but normally is so small that it likewise need not be 65 ing pulse, the output appearing at the collector of tran~
gated off’ during the “dump” period.
Referring now to FIG. 5, a speci?c embodiment of
sistor T5 (phase angle of 180°) is applied to the base of
transistor T1. The application of this negative feedback,
at a time when the envelope wave form at the output
the invention generally described in connection with FIG.
terminal is approaching a maximum, rapidly removes the
4‘ is shown. The input signal, for example the pulsed
radio frequency signal illustrated in FIG. 1, is applied 70 energy stored in the crystal and causes the output wave
form to return to Zero very rapidly. In a circuit which
via input terminal 8 through coupling resistor 22 and
has
been satisfactorily operated, which was designed to
capacitor 24 to the base of transistor T1 at a reference
have a minimum dynamic range of greater than 30 db,
phase angle of 0°. The ampli?ed signal appearing at the
the system gain was su?iciently greater than 30 db that
collector of the transistor is applied across crystal 10, 75 it was unnecessary to remove the input signal from the
3,056,890“
6‘,
put terminal of said ampli?er and the input terminal of
said crystal, electronic switching means in said feedback
base of transistor T1 during the “dump” period of the
crystal. In the event the initial Q of crystal 10 is in
sui?cient to give a perfectly linear build up, positive
feedback may be applied from the input of the ?nal stage
of the ampli?er over connection 20 through resistor 44
to the base of transistor T1. It has been found that the
path operable in synchronism with said pulsed input sig
nal for successively opening said feedback path for the
duration of each input pulse, and thereafter closing said
feedback path for a predetermined interval at the termina
tion of each input pulse for applying a 180° out-of-phase
magnitude of the positive feedback signal required to
quenching signal to said crystal, and a positive feedback
insure proper integration characteristics for the crystal
path connected from said ampli?er to the input terminal
is of sut?ciently small magnitude that it also need not
10 of said crystal for continuously applying a positive feed
be gated off during the “dump” period.
back signal to said crystal.
This circuit may be operated over a wide range of
4. An electronic wave shaping circuit comprising a
pulse repetition rates without circuit changes, for example
resonator, said resonator comprising a high Q crystal
between 20 cycles per second to 1000‘ cycles per second,
having input and output terminals, means for continuously
with approximately the same fast “dump” time regard
less of the repetition frequency. The “dump” time is 15 applying pulsed radio frequency input signals to the input
terminal of said crystal, an ampli?er connected to the out
about 200 microseconds thus allowing almost the total
put terminal of said crystal and arranged to produce an
time of each pulse period for the integration function.
output signal 180° out of phase relative to said input sig
The use of transistor circuitry contributes to low power
nals, a negative feedback path connected between the out
consumption, the circuit is very de?nitely less expensive
than the electro-mechanical resonators and associated 20 put of said ampli?er and the input terminal of said crystal,
and switching means in said negative feedback path in
circuitry, and the total volume occupied by the present
cluding a normally non-conducting gating circuit operable
system is vapproximately 10 cubic inches as opposed to
in synchronism with said pulsed input signal to be ren
the approximately 100 cubic inches for a system employ
dered conducting for a predetermined interval at the termi
ing the electro-mechanical resonator. Additionally, this
circuit, by merely changing the value of circuit compo 25 nation of each input pulse for applying 180° out-of-phase
quenching signals to said crystal.
nents, can be designed to accommodate a very wide range
5. A keyed ?lter system comprising a resonator, said
of crystal frequencies (i.e., wide range of RP‘. frequencies
resonator comprising a high Q crystal having input and
in the pulses) in contradistinction to the electro-mechani
output terminals, means for continuously applying pulsed
cal ?lter where each resonator is limited to use at a
radio
frequency input signals to the input terminal of said
30
single frequency.
crystal,
a degenerative ampli?er having an odd number
While there has been shown and described a speci?c
of stages connected to the output terminal of said crystal
embodiment of applicants’ invention, it will be apparent
and arranged to produce an ampli?ed output signal 180°
to those skilled in the art that many modi?cations and
out-of-phase relative to the input signal, a negative feed
variations can be made within the scope and spirit of
35 back path connected between the output of said ampli?er
the invention as de?ned in the appended claims.
and the input terminal of said crystal, switching means in
What is claimed is:
said negative feedback path including a normally non
1. A wave shaping circuit including a resonator, said
conducting gating circuit and means for applying a
resonator comprising a crystal having input and output
rounded gating pulse to said gating circuit in synchronism
terminals, means for applying a pulsed radio frequency 40 with said pulsed input signal to cause said gating circuit
input signal to the input terminal of said crystal, an
to conduct for a predetermined interval at the termina~
ampli?er circuit including input and output terminals
tion of each input pulse whereby to apply 180° out-of
having its input terminal connected to the output termi
phase quenching signals to said crystal.
nal of said crystal, a feedback path connected between
6. A keyed ?lter system for pulsed radio frequency sig
the output terminal of said ampli?er and the input termi
nals comprising, a high Q resonator consisting of a crystal
45
nal of said crystal, and switching means in said feedback
having input and output terminals, means for continuously
path operable in synchronism with said pulsed input signal
applying radio frequency pulses to the input terminal of
for successively opening said feedback path for the dura
said crystal, a portion of the energy in each pulse being
tion of each input pulse and closing said feedback path
stored in said crystal and a portion being passed to its
for a predetermined short interval at the termination of
output terminal, a degenerative ampli?er having input and
each pulse for applying a quenching signal to the input 50 output terminals, means connecting the output terminal of
terminal of said crystal to rapidly remove the energy
said crystal to the input terminal of said ampli?er, said
stored therein ‘during the duration of each pulse.
ampli?er being operative to amplify the signal at the out
2. A wave shaping circuit comprising a high Q crystal
put of said crystal to produce a signal 180° out-of-phase
having input and output terminals, means for continuous 55 relative thereto, a feedback path connected between the
ly applying pulsed radio frequency input signals to the
output terminal of said ampli?er and the input terminal
input terminal of said crystal, a degenerative ampli?er
of said crystal, switching means in said feedback path
including input and output terminals having its input
including a gating circuit arranged to be opened during
terminal connected to the output terminals of said crystal,
the period of each input pulse and to be closed for a pre
a feedback path connected between the output terminal
determined interval synchronously with the termination of
of said ampli?er and the input terminal of said crystal,
each input pulse to apply the output of said ampli?er to
and electronic switching means in said feedback path
the input terminal of said crystal for rapidly removing
operable in synchronism with said pulsed input signal for
from the crystal the energy stored therein during each
successively opening said feedback path for the duration
of each input pulse, and thereafter closing said feedback
path for a predetermined interval at the termination of
input pulse.
5
each input pulse for applying a 180° out-of-phase quench
ing signal to said crystal.
3. A wave shaping circuit comprising a high Q crystal
having input and output terminals, means for continu 70
ously applying pulsed radio frequency input signals to
7. A keyed ?lter system comprising, a high Q resonator
consisting of a crystal having an output terminal and an
input circuit for receiving radio frequency pulses having
a duration which is short relative to the total rise time
of the exponential frequency response characteristic of
said resonator, a portion of the radio frequency energy
in each pulse being stored in said crystal and a portion
being passed to its output terminal, an ampli?er having
input and output terminals, means connecting the output
terminal of said crystal to the input terminal of said ampli
terminal connected to the output terminals of said crys
tal, a negative feedback path connected between the out 75 ?er, said ampli?er being operative to produce at its output
the input terminal of said crystal, a degenerative ampli
?er including input and output terminals having its input
3,056,890‘
7
terminal; a signal 180° out-of-phase relative to the signal
at the output terminal of said crystal, a feedback path‘
connected between the output terminal of said ampli?er
and the input circuit of said crystal,_and a switching circuit in said feedback path arranged to be opened during 5
252x650
2,8813 17
Spencer —————————— ——’-—e— Jan' 13, I953
Himke ———————————————— —— APr- 7, 1959
the vperiod of eachlradio frequency pulse and to be closed
2,881,390
Wmn ————————————————— -— APT- 7’ 1959
for. a. predetermined short time interval synchronously
with theterrninationof each radio frequency pulse to
References Cited inthe ?le of this patent
UNITED, STATES PATENTS
V
OTHER REFERENCES
apply" the output of said'arnpli?er to the input circuit of
A Balanced Modulator Super-Regenerative Circuit, byv
saidcrystal thereby to rapidly’ remove from thencrystal, 10, Roberts, QST, July 1932, pp. 19, 20.
energy stored therein during each input pulse.
Документ
Категория
Без категории
Просмотров
0
Размер файла
627 Кб
Теги
1/--страниц
Пожаловаться на содержимое документа