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Патент USA US2411547

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Nov. 26, 1946.
E. LABIN ET AL
2,411,547
PULSE ‘WIDTH MEASURING SYSTEM
Filed March 26, 1943
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Patented Nov. 26, 1946
@FHQE
UNITED STATES
2,411,547
PULSE WIDTH MEASURING SYSTEM
Emile Labin, New York, and Donald D. Grieg,
Forest Hills, N. Y., assignors to Federal Tole»
phone and Radio Corporation, Newark, N. 3., a
corporation of Delaware
Application March 26, 1943, Serial No. 480,624
13 Claims. (Cl. 171-495)
1
This invention relates to radio impulse systems
and more particularly to the measurement of the
duration or width of pulses.
One of the objects of this invention is to provide
a relatively simple method and means for measur
Z
duced oscillations of the circuit. The tuning con~
trol of the circuit may be calibrated to give a di
rect reading of the pulse width when the greatest
maximum or minimum indication for the undula
tion is obtained.
‘
Another object of the invention is to provide a
For a further understanding of the invention,
reference may be had to the following detailed de
scription to be read in connection with the accom
determined by a simple operation. I
In accordance with our invention, a pulse meas-'
to our invention; and
Fig. 2 is a graphical illustration of the steps car»
ing the widtlm of substantially rectangularly
shaped pulses.
panying drawing, in which:
pulse width measuring system requiring only a
Fig. l is a schematic wiring and block diagram
few parts and by which the width of pulse shapes 10
of the pulse width measuring system according
or substantially rectangular form can be readily
ried out by the system during a tuning operation.
urement is made by applying a train of the pulses
Referring to Fig. 1, the pulse width measuring
to a shock excitable resonant circuit whereby the 15
circuit is shown provided with an input connection
leading and trailing edges of each pulse shock ex
l0 having a coupling stage i2 which is preferably
cite the circuit to produce oscillations. The oscil
a screen grid stage, whereby positive pulses i5 are
lations produced by the edges of each pulse com~
inverted as indicated at 15a for application to the
blue to form an undulation following the trailing
edge of the pulse. The oscillations which nor 20 resonant circuit it. In addition to inverting the
pulses this coupling stage presents .a high re
mally follow this undulation are damped out by
sistance with respect to the applied voltage so
providing a damping shunt connection across the
that the total current flow into the following cir
resonant circuit. This shunt connection includes
cuit is an exact replica of the applied pulse. Comm
a vacuum tube which when made conductive pro~
vides a low resistance path across the resonant 25 necting the output I‘! of the coupling stage iii to
the resonant circuit i8 is a resistor R. The reso
nant circuit includes an adjustable condenser C
and an inductance coil .L. The condenser and
~ing energy. The grid of the tube is arranged to
the coil are connected in parallel. Connected
receive a negative voltage for the duration of each
pulse while the pulse is applied to the resonant 30 across the terminals l8 and 19 of the inductance
coil L is a damping tube 20. The output con
circuit. The anode and cathode of the tube are so
nection ii is connected by lead 22 to a grid 23
connected that when the polarity of the current
of the tube. The cathode it is connected to the
in the resonant circuit is in one direction it blocks
terminal i8 and the anode ‘25 is connected to the
conduction by the tube and when in the opposite
direction it unblocks the tube. By this arrange“ 35 terminal i9._ The terminal i9 is also connected
to a source of positive potential 13+. Condenser
ment, the tube operates to suppress the oscilla
01 represents a low return impedance to ground
tions which would normally follow the desired un
and is not part of the resonant circuit.
_
dulation by the tubebecoming conductive when the
The potential or" the resonant circuit present
voltage across the resonant circuit changes in no“
at the terminal i8 is talsen o? at an output 28 for- ‘
larity at the end of the undulation and when the
circuit thereby lowering the “Q” of the circuit
to such a value as to absorb quickly the oscillat~
voltage of the applied pulse becomes zero.
The system according to our invention will,
therefore, produce an undulatlon ‘following the
trailing edge of each pulse and thereafter sup“
press all further oscillations until the next sucw
ceeding pulse is applied to the circuit.
By providing the resonant circuit with an am
pli?er stage and a maximizing-and minimizing in“
dicating meter or other maximizing or minimiz—
application to an ampli?er stage 30 which is pref“
erably arranged to operate as a, class "C" am
pli?er. The anode connection 32 oi.‘ the ampli?er
30 is connected to a meter 31 the opposite side or
- which is connected to a positive potential 13+. '
The
long meter
as it gives
31 may
anbeindication
of any suitable
of peak
character
voltage of
the undulations passed by the ampli?er 30 to the
anode circuit 32.
The operation of the system of
1 will be bet~
ing indicator, such as a cathode ray oscillograph, 60
ter understood by reference to Fig. 2 in which all
an operator can easily determine when the circuit .
curves are applied to the same time base. Curve
is tuned to the fractional period corresponding
a represents the pulse input after passing the cou
to the duration of the pulse. That is to say, the
leading and trailing edges of the pulse are then
pling
this point
stage.in the
Thus,
circuit.
the pulses
Should
l5 the
are input
negative
pulses
in either direct step or opposition with the in»
aerate’?
' 3
be negative instead of positive the coupling stage
l2 could be replaced with an input resistance.
For purposes of illustration, the pulses i5 of curve
a may also be regarded as the voltage across the
resistor R since the total current that ?ows into
the tuned circuit will be an‘exact replica of the
applied input voltage.
'
ment for the condition of curve 23 will give a meter
indication M1 while the tuning adjustment rep
resented by curves 0, d and e will give meter indi_
.catlons Ma, Ma and M4, respectively. These in
dications are represented on curve 0 whereby a
comparison may be easily seen. It will be clear
that the undulation indication 55c of curve 0
Curve b represents the oscillations at the output‘ 28 of the circuit i6 when the circuit is tuned to a
wavelength or period tl which is less than twice
represents the maximum obtainable by adjust
ment of the condenser C. Thus, the period 22
which represents adjustment of the condenser C
the duration of the pulse i5. Curve 0 represents
the output potential of the circuit is when the
circuit is tuned to a wavelength it’ which is sub
stantially twice the duration of‘ the pulse i5.
Curve d represents the output potential of the cir 15
period which is substantially twice the duration
of the pulse 45. The calibration of the condenser
cuit it when the circuit is tuned to a wavelength ,
for the condition illustrated in curve 0 is the
C, of course, will be such as to give a direct indi=
cation in microseconds of the width of the pulse
maximized, this indication being dependent only
it which is greater than twice the duration of the
on the passive elements C and L.
pulse iii. Curve 2 represents the output potential
,For increased measurement range, additional
of the circuit id when the circuit is tuned to a
inductance coils may be provided together with
wavelength it which is in'the order of an odd 20 switching means for substituting selectively a coil
multiple or‘ the duration of the pulse.
'
of desired inductance value for the inductance
Referring particularly to the curves (1 and b,
coil L. In that case, the condenser C will be pro
the leading edge Iii of the pulse will initiate an
vided with a separate calibration for each coll.
oscillation élii. When the trailing edge 53 is ap- - A tuning arrangement of this character is dis
plied to the circuit it, it initiates a second oscil 25 closed in the copending application of Donald D.
lation dd. Since the tuning of the circuit id is
Grieg entitled “Measuring system,” Serial-No.
out of step with the width of the pulse 15, the
475,734, ?led February 13, 1943.
oscillations 62 and d3 are out of step. These
In the case of the circuit being tuned so that
oscillations combine algebraically to produce an
an odd multiple of half-periods occur during the
30 pulse width, an example is indicated by curve 2,
undulation 6S. '
Assuming that the damping tube 29 is removed
wherein the wavelength is 11/2 times the pulse a
from the circuit of Fig. 1, the oscillations 432 and
width. It will be noted ‘that the maximized un
44 will continue to combine beyond the undula
dulation 65a is less than the maximum undulation 55 thereby producing a damped oscillation
tion indication 1355c (curve 0) . The reason for this
4i‘ shown in broken lines in curve I). For a reso 35 difference will be readily apparent from curve e
nant circuit of relatively high “Q" the oscillation
because of the damped condition of the oscilla
48 would be present when the next succeeding
tion 52c produced by the leading edge iii. The
pulse 15?) is applied to the circuit. It will be
second positive undulation d2 of the oscillation
apparent from the curve b that this oscillation QB
die is considerably less than the ?rst positive
in such case will combine with the oscillations. 40 undulatlon 58. Since it is the second undulation
produced by the pulse i5b thereby affecting the
52 which is in step with the undulation tide pro
shape of the undulation it? which would be nor
duced by the trailing edge 53, the undulation lite
mally produced‘ by the pulse I52}.
resulting from the combining action of the undu
As hereinbefore explained the damping tube 2b
lation' lite and 52 is less than the maximized indi
is provided to damp out the oscillations such as 4. cation él‘dc. Thus, while the represents a ‘maxi
56 which would normally follow undulations 45,
mized indication for a wavelength in the order of
it, etc, so that the oscillations produced by one
an odd multiple of the pulse width, it is clear
pulse will not affect the oscillations produced by
that such maximizing operation does not produce
the next succeeding pulse. This damping out
the greatest maximum indication possible.
operation is performed when the tube 2b is ren- .
dered conductive as when the undulation 6-5
reaches the zero potential oi’ vthe curve ‘b. Thus,
when the energy of the circuit 56 starts to re~
verse in polarity at the terminals i8 and it, the
tube is rendered conductive thereby reducing the
In general a maxima is obtained when the
period of the tuned circuit is such that:
l Z=;T
where w is the width of the pulse and n1 is an odd
"Q” of the circuit It to such a value as to absorb
integer corresponding to the number of half pe
the oscillatory energy of the circuit. This absorp
riods occurring during the pulse time.
tion of the oscillatory energy is such as to sub
'
A minima is obtained when:
stantially completely damp out the oscillations
that would normally follow the undulation 65. 60
This results in a zero potential line 5Q following
the undulation 45 until the next succeeding pulse
is applied to the circuit.
The conduction of the tube Ed is prevented
during the application of a pulse to‘ the circuit
is by the connection 22 whereby the negative
energy of the pulse (curve a) is applied to the
grid 23 of tube. This insures the blocking of
the tube against conduction for the duration of
the pulse, and after the trailing edge of the pulse,
the undulation {it being positive at the terminal
l8 prevents the tube from conduction for thew
duration of the undulation.
'
By adjusting the condenser C, the undulation
£35 may be minimized or maximized. The adjust
where m is an even integer corresponding to the
number of half periods within the pulse time.
In order to prevent the undulation 5! from
being'applied to the meter at for the tuning con
dition illustrated in curve e, the negative poten
tial of the pulse 55 (curve a) is applied to the
ampli?er stage 36 through a connection 55. This
negative potential for the duration of the pulse
i5 is used ‘to block ‘out the amplifier in known
manner so that for the duration of the pulse any
positive undulations produced will not be applied
to the meter 36}. This blocking of undulation 5|
is indicated at dia.
While we have shown and described the prin
aai 1,54"?
t3
vacuum tube connected across said circuit, and
means to bias the tube to cut-o?‘ for the dura
tion of the pulse, the polarity of the circuit conmodifications may be made therein without de~
nections across the tube being such during the
parting from the invention. For example, in
‘stead of maximizing, the system may be arranged 5 formation of said undulation as to maintain the
tube at cut-off for the duration of said undula~
to give pulse width measurements by a minimiz
tion and the change in polarity of said connec~
ing operation. It is our aim therefore to cover
5
.
ciples of our invention in connection with speci?c
apparatus, we recognize that various changes and
in the appended claims all such changes and
modi?cations as fall within the scope of the in
vention.
We claim:
1. A method of measuring the duration of
tions at the end of said undulation operating to
produce conduction in said tube to shunt said
circuit.
8. The system de?ned in claim. Zl, wherein the
means for indicating energy of said undulation
includes an ampli?er arranged to threshold clip
pulses of a given shape having abrupt changes
the undulations.
at the leading and trailing edges thereof, com
9. The system de?ned in claim ll, wherein the
prising shock exciting a resonant circuit by the 15
leading and trailing edges of a train of such
pulses, the oscillations initiated by the edges of
each pulse combining to form an undulation fol
means for indicating energy of said undulation
includes an ampli?er arranged to threshold clip
the undulations and means connected to the in~
put of the shock excitable circuit to apply the
lowing the trailing edge of the pulse, damping
out the oscillations which normally follow said 20 energy of the pulses to the ampli?er to block
operation thereof for the duration of each or"
undulation so that the oscillations produced by
the pulses so that undulations produced by the
one pulse will not a?ect the oscillations produced
leading edge prior the occurrence of the trailing
by the next succeeding pulse, and tuning the cir
edge of a pulse will not be passed by said ampli
cuit until the undulation reaches a size limit such
?er.
as its greatest maximum, whereby one-half the
10. A system for translating the pulses of a
period-of the frequency to which the circuit is
train of like pulses into undulations comprising
tuned represents a timing at a given multiple of
a shock excitable circuit, means to apply the train
>
of pulses to the circuit to produce oscillations
2. The method de?ned in claim 1, wherein the
damping out of oscillations is controlled by a 30 therein in response to the leading and trailing
edges of each of the pulses, the oscillations ini
given polarity condition across the tuned circuit
tiated by the leading edge of a pulse combining
after occurrence of each pulse.
/
to form an undulation following the trailing edge
3. The method de?ned in claim 1, wherein the
of the pulse, a vacuum tube having anode, cath
damping out of the oscillations is produced by
ode and grid electrodes, means connecting the
blocking the energy of the oscillations when the
anode and cathode electrodes across said circuit,
energy changes polarity at the end of said undu
and means to apply said train of pulses to said
lation.
grid electrode to block said tube for the duration
4. A system for measuring the duration of a
of each pulse, the anode and cathode connections
pulse comprising a shock excitable circuit, means
- to apply a train of the pulses to the circuit to 40 being arranged to produce a blocking potential
for the tube for the duration of said undulation
produce separate oscillations therein in response
and an unblocking potential for said tube upon
to the leading and trailing edges of each or" the
initiation of a voltage having polarity opposite
pulses, the oscillations initiated by the leading
to the polarity of said undulation, whereby said
and trailing edges of each pulse combining to
form. an undulation following the trailing edge ' tube clamps out oscillatory energy in said circuit
following said undulation.
or" the pulse, means to damp out the oscillations
11. A circuit comprising a plurality of circuit
which normally follow said undulation so that
elements connected in parallel circuit arrange
the oscillations of one pulse will not affect oscilu
the duration of the pulse.
ment, one of said elements being a condenser, a
means to indicate energy of said undulation, and 50 second being an inductance and a third being a
damping tube having the cathode and anode elec
means to_tune the circuit until said undulation
trodes thereof connected in the parallel circuit,
reaches a size limit such as its greatest maximum,
a resistor, an input for negative pulses connected
whereby one-half the period of the frequency at
lations produced by the next succeeding pulse,
through said resistor to said parallel circuit, said
which the circuit is tuned represents a given mul
55 tube having a grid, and means connecting said
tiple of the duration of the pulse.
input to said grid.
5. The system de?ned in claim 4, wherein the
12. The circuit de?ned in claim 11, in combi—
means to damp out the oscillations comprises a
low resistance shunt connection across said cir
cuit and means responsive to energy 01! said pulse
nation with an energy indicator including an am»
plifler, and means connecting the parallel circuit
to control the blocking and unblocking of said to to the input of said amplifier.
13. The circuit de?ned in claim ‘ii in combine.“
shunt connection.
tion with an energy indicator including an arm
6. The system de?ned in claim 4, wherein the
pli?er, means connecting the parallel circuit to
means to damp out the oscillations " comprises a
the input of said amplifier, and means to connect
low resistance shunt connection across said cir—
cuit and means responsive to energy of said pulse 65 the input to said parallel circuit to said ampli?er
to maintain the ampli?er block during applica
and oscillatory energy from said circuit of polar
tion of a negative pulse to the input of said cir
ity opposite the polarity of said undulation to
cuit.
block the shunt connection.
LHBIN.
7. The system de?ned in claim Li, wherein the
DONALD D‘. GRIEG.
means to damp out the oscillations comprises a 70
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