Патент USA US2595879

May 6, 1952
p. E. NORGAARD
2,595,876
RADIO PULSE-ECHO LOCATING EQUIPMENT
Filed Feb. 2, 1944
5 Sheeté-Sheet 1
Donald E. NoPgaar-d;
by WW6 2M4“;
His Attorney.
May 6, 1952
-
D. E. NORGAARD
2,595,876
RADIO PULSE-ECHO LOCATING EQUIPMENT
Filed Feb. 2, 1944
3 sheets-sheet 2 \
TRAIN AND ELEVATION
TRACKING CIRCUITS
76 R55
‘ Inventor:
Donald ENcrgaard,
b
‘y
WW 6? J
His Attorney.
.
May 6, 1952
2,595,876
D. E. NORGAARD
RADIO PULSE-ECHO LOCATING EQUIPMENT
Filed Feb. 2, 1944
3 Sheets-Sheet 5
Inventor“
Donald 'E. Norjgaard,
by
an»)
H IS Attorney
Patented May 6, 1952
2,595,876
UNITED STATES PATENT OFFICE
- RADIO P‘U‘LSE-EGi-‘H;v5
EQUIPRIENT _
Donald E. Norgaard, Scotia, N; Y.-, assignor to
General Electric Company, a corporation of
New York
Application February 2, 1944, Serial No. 520,724
20 Claims. (Cl. 343-?)
‘
1
The present invention relates to locating
equipment of the type utilizing echoes of pe
riodic pulses of wave energy from a remote ob-'
ject to determine its location. In such equip
ment the transmitted pulse rate is usually chosen
so that the echoes from objects within the de
sired range arrive during the intervals between
succeeding pulses. Echoes from objects beyond
this range will arrive after the transmission of
a succeeding pulse and accordingly make possi
ble an ambiguous representation.
An object of my invention is to provide an im
proved equipment in which echoes from beyond
2
and causing a sudden increase in potential at
its anode I6. The interruption of current through
the device 9 removes the negative bias from
the device 8, turning the device 8 on and simul
taneously, creating a further negative swing in
the potential on the grid I4, thus driving the
device 9 beyond cut-off. The device 9 remains
at cut-01f for a period determined in part by
magnitude of the current through the device 8
10 and in part by the values of the condenser I5
and resistance I‘! which determine the rate at
which the condenser I5 charges after being
driven negative by the ?ring of the device 8.
the range being investigated do not interfere
After the charging of the condenser I5 the device
with the measurement, presentation, or track— 15 9 begins to become conductive, causing a drop in
ing of the position of a target.
'
potential at its anode I6 and a rise in potential
A further object of my invention is to provide
across the cathode resistor I2 which biases the
an improved automatic range tracking circuit.
device 8 toward cut-o?. This action continues
The novel features which I believe to be char
regeneratively until device 8 is driven beyond
acteristic of my invention are set forth with pare 20 cut-'oii, where it is held until triggered again
ticularity in the appended claims. My inven~
by the following positive peak ‘I.
tion itself, however, both as to its organization
The voltage at the anode I6, namely the out
and method of operation, together with fur
put of the delay multivibrator comprising devices
ther objects and advantages thereof, may best
8 and 9, is applied through a small condenser I3
be understood by referenceto the‘ following de 25 to a ‘winding I3 of a pulse transformer I9 having
scription taken in connection with the accom—
a winding 28 in which is induced a voltage of
panying drawings in which Figs. la and lb when
opposite sign to that appearing across the wind
placed side by. side form a diagram of equipment
ing I8. The voltage induced in the winding 28
embodying my invention; and Figs. 2 and 3 are
corresponds roughly to the slope of the wave ap
diagrams explaining its operation.
pearing on anode I6 and is applied to the grid
Referring to the drawings, in the upper section
2| of a device 22 normally biased to cut-off. The
of Fig. 1a there is shown the pulse frequency
negative induced voltage in the winding 20 oc
control which comprises a multivibrator I con
curring at the leading end of the delay output
trolled by an oscillator 2 so as to have negative
voltage at the anode It drives the grid 2I still
output pulses, indicated at 3, at the desired uni= 35 further negative and accordingly has no effect.
form repetition rate or pulse frequency which
At the trailing (negative slope) end of the volt
may be such that echoes or re?ections from more
age at the anode I6 a positive voltage is induced
remote objects may be received prior to the
in the winding 20 which drives the grid 2I>in
transmission of a succeeding pulse of radio
the positive direction thereby causing a sudden
waves. The negative output pulse‘ of the pulse 40 flow of current through the winding i8 thus in
frequency multivibrator is fed through a dife
ducing a further voltage in the winding 29 forc
ing the grid 2| more positive and causing a
ferentiation' circuit 4 to the grid 5 of a device
6, which is biased on by the positive peaks 1
cumulative increase in, current until the grid
coincident with the trailing edge of the pulse
voltage reaches a value such that a further
frequency multivibrator outputto trigger adei 45 increase in grid potential causes insufficient in-I
lay multivibrator comprising devices 8 and 9 con
crease in current through the winding I8 to
nected across the power supply through plate
maintain ‘this “runaway” condition. The cur
resistors I9 and I I and a common cathode resise
rent‘ in winding I8 then begins to- collapse and
tor I2. The device 9 is normally conducting and
induces a negative voltage in the winding 20
the device 8 is normally biased'o? by the cure 50 thereby driving the grid 2I negative and causing
rent in the cathode resistor.’ When the device
a cumulative decrease in the current. The result
E5 is biased on, the voltage drop through the com
is a pulse of current in the winding I8 having a
rnon plate resistor It applies a negative swing
Width of the order of one microsecond. This
to thegrid I4 of the device 9 through a coupling
condenser :5, thus biasing the‘device 9 to cuteoff
current induces a corresponding voltage in a
winding 23 indicated at 23a which is applied
2,595,876
through a conductor 24 to synchronize a pulse
transmitter 25 connected through a well-known
form of Transmit-Receive device, or TR box,
26 to a directional antenna 21.
From the above described circuits it is apparent
that narrow, or brief, pulses of radio waves are
transmitted from the antenna 2'! at intervals
determined by the output of the pulse frequency
sent echoes of the transmitted pulses AI, A2 from
an object so remote from the equipment that the _
echoes from one pulse do not return to the equip
ment until after the transmission of a succeeding
pulse. Under this condition it is obvious that a
?xed pulse rate makes possible an ambiguous
representation since the operator might think
that the echoes CI, C2 were from an object nearer
than the object corresponding to the echoes BI,
multivibrator I but that, since the pulses are
transmitted at the trailing ends of the output 10 B2, B3. By continually increasisng the pulse rate
as indicated in line 41, the echoes B occur at the
wave of the delay multivibrator 8, 9, it is possible
same spacing with reference to the transmitted
to vary the time of pulse transmission by varying
pulses A, but the echoes C continually shift along
(modulating) the width of the square wave ap
the time scale. In line 41 the echoes C are repre
pearing on anode I6 while keeping the average
15 sented as occurring ?rst to the left, then coin
pulse rate constant.
cident with, and then to the right of the echoes
The control of the time phase of the pulse
B. A similar type of represeentation would be
transmission with reference to the output of the
obtained if the pulse rate for line 41 were de
pulse frequency multivibrator I consists of a
creasing instead of increasing. In actual prac~
multivibrator 28 having a square wave output of
a relatively low frequency, such as 100 cycles. 20 tice the transmitted pulses A and the echoes B
would be superimposed on the viewing screen of
The output frequency of the multivibrator is not
the cathode ray tube as indicated in line 48, while
critical and may be subject to other wide varia
the echoes C would be scattered on both sides
tions. The output of the multivibrator 28, which
of the echoes B and would be of much lower in
is indicated at 29, is fed through an integrating
tensity (as indicated by the dotted lines) than
circuit comprising a condenser 30 and resistance
the superimposed pulses and echoes A and B.
3|. This integrating circuit changes the square
In practice the echoes C will not be visible. By
wave output 29 to a triangular wave shape at
frequency or phase modulation of the pulse rate
terminal 33. The voltage at terminal 33 is ap
the danger of ambiguity due to reflections from
plied to the control grid of device 34 and the
objects beyond the desired range of the equip
ampli?ed output is fed through a second integra
ment is‘eliminated. The frequency modulated
tion circuit comprising condenser 3'! and. resist
pulse rate also eliminates similar interference due
ance 35. In this integration circuit the triangular
to the operation of more than one equipment in
wave shape is converted to a double parabolic
the same locality. If such interference develops,
wave shape indicated at 39. A controllable frac
it can easily be eliminated by changing the fre
tion of the double parabolic voltage appearing
quency modulation while maintaining the aver
across the resistance 38 is fed through a slider
age pulse rate at a constant value.
40 to an ampli?er 4| having an output resistance
It is desirable that the frequency modulation
42 connected by means of coupling condenser 36
be linear so that echoes C will be uniformly spread
to the control grid 43 of the device 8. The grid
43 is also connected through a slider 44 to a volt 40 on either side of the echoes B. This is accom
plished by the double parabolic variation of the
age divider 45 which determines the average grid
grid bias of the delay multivibrator and results
bias. The potential at the grid 43 accordingly
in triangular frequency modulation. If the fre
consists of an average bias on which is super
quency modulation is not linear, there is a pos
imposed a signal having the double parabolic wave
shape indicated at 39. At the positive peaks of he as sibility that the unwanted echoes C will bunch
together on the viewing screen and give a false
the signal on the grid 43' the current through
indication.
the device 8 is larger and the condenser I5 is
The output pulse 23a of the pulse transformer
driven more negative upon ?ring of the device 8.
I9 which synchronizes the pulse transmitter is
This means that a longer time is taken to re
charge the condenser I5 and that the trailing 50 also fed to a sweep circuit at the lower part of
Fig. 1b to generate sawtooth sweep voltages
end of the output voltage appearing at the anode
which start synchronously with each transmitted
I6 will occur later. The time phase of the trail
pulse and increase linearly for that part of the
ing edge of the output voltage at the anode I6
interval between the transmitted pulses cor
varies directly with the variation in potential
of the grid 43. The pulse rate of the transmitter 55 responding to the range investigated by the
equipment. The generation of the sweep voltage
which is synchronized with the trailing end of
is controlled by a sweep timing multivibrator
the output voltage at the anode I6 will accord
comprising devices 49 and 50 having plate re
ingly vary in time phase in a manner which can
sistors 5| and 52 and a common cathode resistor
60 53. The device 50 is normally conducting and
the device 49 is normally biased off by the cur
The utility of the frequency or phase modu
rent flowing in the cathode ‘resistor 53. The
lated pulse rate is illustrated in Fig. 3 where line
be described as a frequency or phase modulated
pulse rate.
multivibrator is keyed by a device 54 connected to
46 represents a developed time scale of pulses and
the plate resistor 5| and having its control grid
echoes with a ?xed pulse rate, line 4'! represents
a developed time scale with a continually increas 65 55 biased on by the pulse 23a. The current
through the device 54 coincident with the pulse
ing pulse rate, and line 48 represents the trace
23a causes a drop in voltage at the anode 56 of
on the viewing screen of a cathode ray tube ob
the device 49 which is applied through a con
tained with the frequency or phase modulated
denser 51 to the grid 58 of the device 50 biasing
pulse rate. Referring to line 46, Al, A2, A3, and
A4 represent successive transmitted pulses, AI 70 the device 56 to cut-off. The interruption of
current through the device 50 removes the nega
being the ?rst of a series, BI, B2, and B3 repre
tive bias from the device 49 which now conducts
sent corresponding echoes of the pulses AI, A2,
and causes a negative bias on the device 50 hold
and A3 from an object close enough to the equip
ing it off. The. length of time the device 50
ment so that the echoes return before the trans
mission of a succeeding pulse, and CI, C2 repre 75 remains at cut-off (the delay or sweep interval)
5
2,595,876
is determined in part by the amount of the cur
rent ?owing through the device 49 and in part
6
which now conducts and creates a further nega
tive voltage on the grid 92 of device 84, holding
by the values of the condenser 51 and resistance
the device 84 off. The device 83 remains on (and
59. The current through the device 49 may be
the device 84 remains off) for an interval de
varied by a potentiometer 60 connected to its
termined by the time required for the condenser
control grid BI . The output voltage of the multi
9I to charge through a resistance 93. This time
vibrator appearing at the anode 52 of the de
is determined in part by the values of the con
vice 58 comprises a square wave voltage starting
denser 9| and resistance 93 and in part by the
coincident with the pulse ‘23a and ending at a
magnitude of the current through the device 83.
later time determined by the values of the con
The current through device 83 is controlled by
denser 5‘! and the resistance 59 and the ad
the bias on its control grid 94. At the end of this
justment of the potentiometer 60. This output
interval, which may be termed the‘range delay
voltage is applied to the grid 63 of a device 84
interval, the device 84 is biased on and the device
normally biased oil and causes a how of current
83 is biased off. During the range delay interval
through a cathode resistor 65 during the delay 15 a square wave output voltage appears at the
(sweep) interval of the multivibrator. The volt
anode 95 of the device 84 having its leading edge
age across the cathode resistor 55 is applied to
96 synchronized with the pulse 230. and its trail
the cathode 66 of a diode 61 connected between
ing edge 91 positionedbetween the dotted lines 98
the cathode resistor and condensers 68 and 89.
at a point determined by the bias on the control
During the delay interval of the multivibrator 20 grid 94. When the equipment is being manually
49, 50 (the sweep interval) the diode 61 is biased
operated, the bias on the grid 94 (the range delay
oil and the condenser‘ 58 charges at a substan
bias) is obtained from the slider 99 through a
tially linear rate through a resistance ‘I0 pro
contact I00 and a switch IOI.
V
ducing a constantly increasing voltage at a ter
The output of the range delay multivibrator,
minal ‘II. At the end of the delay interval of 25 which consists of a square Wave voltage having
the multivibrator, the voltage across the cathode
a duration equal to the percentage of theaverage
resistor 65 returns to ground and the condenser
interval between transmitted pulses determined
68 discharges through the diode 61 and through
by the setting of the slider 99, is fed through a
resistance 65. As indicated in the diagram ad
diode I92 to a range bridge in the lower part of
jacent terminal ‘II, the rate of discharge of the
Fig. 1a. The range bridge comprises a voltage
condenser 68 is greater than the rate of charge.
regulator tube I03 connected across a poten
The resultant voltage at the terminal ‘II is a
tiometer I04 and across a condenser I05 in series
saw-tooth voltage which starts coincident with
with resistances I00 and IN and an ammeter I08.
the pulse 23a, increases toa maximum at the
The voltage regulator tube maintains at terminal
end of the delay (sweep) interval'of the multi 35 I09 a voltage which is greater than the voltage
vibrator 49, 50, and then abruptly decreases‘ The
at the anode 95 when the device 84 is conduct~
saw-tooth sweep voltage at the terminal ‘II is
ing. Accordingly no current flows through the
applied through an ampli?er ‘I3 to the horizon
diode I02 to the ammeter I 08 during the intervals
tal de?ection plates 14 of a cathode ray tube ‘I5
between the range delay intervals. During the
producing a horizontal sweep trace on the view 40 range delay intervals the current through the
ing screen which serves as a time or range scale.
device 84 is interrupted and the voltage at its
The sweep trace is deflected vertically by the
anode 95 rises approximately to the voltage of
output of a receiver ‘I6 which is fed, together
the power supply. Current now ?ows to the am
with an aperture pulse. from a conductor 11,
meter I08 through the diode I02 and resistance
through an ampli?er ‘I8 to the vertical deflection 45 l01. At the end of the range delay interval
plates 19 of the cathode ray tube. The aperture
when the voltage at the anode 95 returns to a
pulse, hereinafter described, produces a marker
value less than the voltage at the terminal I09,
- 80. on the viewing screen of the cathode ray tube
the current through the ammeter I08 is inter
which identi?es a particular section of the sweep
rupted. By means of this circuit a constant cur
trace and helps to distinguish the echoes from
rent flows through the ammeter I08 during the
an object at the range marked by the aperture
range delay intervals and no current flows
pulse from other echoes.
through the ammeter during the intervals be
The output of the sweep timing multivibrator
tween the range delay interval. Due to the in—
49, 50 is fed from the cathode resistor 65 to the
tegrating effect of the ammeter, the ammeter
grid 8| of the cathode ray tube through an am 55 reading will be proportional to the percentage of
pli?er 82 to actuate the beam of the cathode ray
the range delay interval to the total interval
tube during the sweep intervals (and to decrease
between transmitted pulses. Some question
or blank the beam intensity intermediate the
might be raised as to the e?ect of the frequency
sweep intervals).
modulation of the pulse rate on the accuracy of
The transmitter synchronizing pulse 23a is also 60 the range measurement. However, since the
used to synchronize a range delay multivibrator
pulse frequency is maintained at a constant
comprising devices 83 and 84 connected to plate
average rate by the oscillator 2, the effect of
resistances 85 and 88 and a common cathode re
frequency modulation of the pulse rate is can
sistor 81. The device 84 is normally conducting
celled by the integrating eifect of the ammeter.
and the device 83, which is normally biased oh“ 65
In addition to obtaining an ammeter indica
by the current in the cathode resistor 87, is
tion of range as a percentage of the average in
triggered on by a device 88 having its control
terval between transmitted pulses, the con
grid 89 connected to the conductor 24 so as to be
denser I05 is charged to a voltage proportional
biased on by the pulse 23a. The flow of current
to this percentage. Since the maximum voltage
through the device 88 during the pulse 23a pro 70 to which the condenser I05 can be charged is
duces a negative voltage swing at the anode 90
somewhat less than the voltage across the volt
of the device 83. This'negative voltage swing
age regulator tube. I03, the voltage on the con
is applied through a condenser 9! to the control
denser can be balanced by adjusting a slider I I0
grid 92 of the device 84'driving the device 84‘ off
on the potentiometer I04. For example, if the
and removing’the negative bias on the device 83
range delay interval were 100% of the pulse in
2,595,876
terval, the right hand terminal of the condenser
I05 would be at almost the potential of the power
supply and the voltage on lead I I I (with respect
to voltage at point I09) could be balanced by
moving the slider H0 to a point near the top of
the potentiometer I04. lit the range delay in
terval were 0% of the pulse interval, the con
denser would be charged to the voltage of the
The motor also drives selsyns I25 which transmit
the position of the slider I I0 to remote points at
which'this information is to be used. By the
operation of the modulator H2, the slider H0 is
maintained in a position at which its voltage
intermediate range delay intervals, tobalance
36,367, ?led July 1, 1948, now Patent 2,471,835,
issued May 31, 1949, which is a continuation-in
part of the present application and assigned to
balances the range delay voltage on the con
denser I05 and provides an indication of the
range as a percentage of the average interval
between transmitted pulses. The modulator
voltage regulator tube and the voltage on the
lead III could be balanced by moving the slider 10 circuits are more particularly described and
claimed in my copending application Serial No.
H0 to the bottom of the potentiometer I04. At
the voltage on lead III the slider H0 should oc
cupy a position from the bottom of the poten
tiometer I04 corresponding to the ratio of the 15 the same assignee as the present invention.
In normal use of the equipment, the operator
range delay interval to the average interval be
keeps the switch IOI closed on contact I00 until
tween transmitted pulses.
a target is located. The slider 99 is then adjust
The di?erence between the voltage at the
ed to position the aperture pulse (generated in a
slider I I0 and the voltage at the conductor III,
manner hereinafter described) so it brackets the
which varies in sign and magnitude with the di
target echo and the switch IOI is then closed on
rection and magnitude of the error in the posi
a contact I25 to bring into operation an auto
tion of the slider H0 with reference to the posi
matic tracking circuit which, in a manner to be
tion of balance corresponding to the range de
presently described, automatically adjusts the
lay, is converted to an alternating voltage, vary
range delay bias on the grid 94 of the range de
ing in polarity and magnitude with the direction
lay multivibrator to keep the target echo brack
and magnitude of the error in the position of
eted by the aperture pulse.
the slider H0 by means of a modulator I_I2 com
prising a transformer H3 having a primary H4
energized from a suitable (e. g. 60 cycle) A.-C.
The output of the range delay multivibrator
83, 84 is fed to the grid I21 of a device I28 which
power supply and having secondary windings I I5
and III; arranged to have induced voltages dur
ing-alternate half cycles of the signs indicated
at the ends of the windings (and to have voltages
of opposite sign during intermediate half cycles).
During the half cycles when the voltages in the
windings H5 and H6 have the indicated signs,
current ?ows in the winding H5 through diodes
has an anode in series With a transmission line
I29 shunted across a resistance I30 equal to its
characteristic impedance and shorted at its re
mote end and which has a cathode I3I in series
with a transmission line I32 shunted at its re
H1 and H8 and no current ?ows through the
winding H6. During these half cycles the mid
point of the winding H5, which is connected to
the conductor III, and the midpoint of the re
iI
mote end by a resistance I33 equal to its charac
teristic impedance. The device I28, which is nor
mally biased off, is biased on at the peaks of the
range delay multivibrator output. When the de
vice I28 conducts (at a grid bias indicated by line
I51 in line B of Fig. 2) a current ?ows through
the resistance I30 and an equal current starts to
?ow toward the remote end of the transmission
sistance H9 connected across the diodes II‘! and
line I29. The current wave flowing down the
H8 accordingly have the same D.-C. potential
transmission line I29 reaches the shorted end
which voltage, as explained above, is a function
after an interval determined by the electrical
of the range delay interval. During the inter
length of the line (e. g., 1/2 microsecond) and is
mediate half cycles when the voltages in the
re?ected. When the reflected current wave
windings H5 and H8 are of opposite sign, cur
reaches the resistance I30, the voltage across
rent flows in the winding H6 through diodes I20
(and the current through) the resistance I30
and I2I and no current ?ows in the winding I I5.
The midpoint of the winding H6, which is con 50 drops to zero, and, since the resistance I30 is
equal to the characteristic impedance of the
nected to the slider H8, has the same D.-C. po
transmission line, there are no further re?ections.
tential as the midpoint of the resistance H9
This results in a negative pulse at terminal I34
when current is ?owing through diodes I20 and
having a magnitude determined by the charac
HI. The condenser I22 is connected across the
resistance H9 to prevent simultaneous flow of 55 teristic impedance of the transmission line and
a width equal to twice the time required for a
current from the windings H5 and H8 at the
voltage or current wave to travel from one end
points between the alternate and intermediate
of the line to the other. At the end of the range
half-cycles. From one aspect the modulator can
delay interval the bias on the grid I 21 is dropped
be considered as a pair of bridge circuits having
diametral terminals at opposite ends of the re 60 below cut-01f, interrupting the current through
the device I28 ‘and causing a similar positive pulse
sistance H9 and intermediate terminals at the
at the terminal I34 coincident with the trailing
midpoints of the resistance and the windings
end of the range delay interval; The ?ow of cur
H5, H6. The voltage at the midpoint of the
rent through the device I28 during the range de
resistance I I9 accordingly shifts at the frequency
of the power supplied to the primary H4 from 65 lay interval, produces a voltage wave which ar
rives at the terminating resistance I33 at a later
the potential of the conductor III to the poten
time determined by the length of the transmis
tial of the slider H0, producing a square wave
sion line I32. Since the resistance I33 is equal to
voltage of the power supply frequency which
the characteristic impedance of the transmission
varies in magnitude and polarity with the error
and direction of the displacement of the slider 70 line I32, there are no reflections and a voltage ap
pears across the resistance I33 having the delay
H0 from the position of balance. This square
interval of the range delay multivibrator but dis
wave voltage is fed through an ampli?er I23 to
placed in time phase an amount equal to the de
a motor I24 which shifts the slider IIO toward
lay of the transmission line I32. Since the trans
the position in which the voltage on the
slider balances the voltage on the conductor III. 75 mission lines I29 and I32 are of substantially the
/
2,595,876’
same length, the trailing edge of the voltage ap
pearing at the resistance 133 is at the center of
10
are symmetrical with respect to the A.-C'. axis,
there would be no change in the average current
through the diodes. If the range delay is less
the positive aperture pulse appearing at the‘ ter’-'
minal I34. From one aspect the voltage appear
than 50% of the average interval between trans
ing at the resistance I33 can be termed a delayed
mitted pulses, the positive peaks of the delayed
range voltage. The voltage at the terminal I34
range voltage will be further displaced from the
is fed to the grid I35 of a clipper I36 which is
A.-C. axis than the negative peaks. This means
normally biased off and is biased on only by the
that the averagecurrent through the diode I49
positive peaks of the aperture pulses. The out:
will be less because the positive peak is further
put of'the clipper, which consists of a negative 10 displaced from the A.-C. axis than the negative
aperture pulse, is fed to a mixer comprising de
peak and the average current through the diode
vices I31 and I38 connected to a common plate
I50 will be greater for the same reason.
A de
resistance I39. The negative aperture pulse is
creasein the average current through the diode
applied to the grid I40 of the device I31. The
£49 means that fewer electrons leave its cathode
output of the receiver 16, which includes the 15 which accordingly is more negative. Similarly,
transmitted pulses and noise voltages as well as
anlincrease in the average current through the
echoes, is applied to the grid I4I of the device
diode I53 means that more electrons arrive at
I38. The output appearing across the plate re
its anode which becomes more negative. The op
sistance I39 consists of the sum of the receiver
posite e?ect would be obtained if the range delay
output voltages and the aperture pulse voltage, 20 were greater than 50 per cent. The net result
as indicated to the left of the plate resistance .I 39.‘
is to charge the condenser I54a more negative
The aperture pulse alone appears at the conduc
(or positive if the range delay is greater than
tor 11. The output of the vmixer is fed to the grid
5.0%), decreasing (or increasing) the range de
I42 of a clipper I43 biased so as to draw current
lay bias on the grid 94. The unidirectional volt
only during that part of the mixer output which 25 age at the terminal I53 is thus a linear function
includes the peak of the aperture pulse. The ‘out
of the ratio of the range delay to the average in
put of the clipper I43, which includes only the
terval ‘between transmitted pulses. It is found
aperture pulse and any coincident echo, appears
that the voltage‘ fed‘ back to the grid 94 by ad
as a negative voltage across a resistance I44, and
justing slider I54 to a suitable position on re
is fed to the grid I45 of an inverter I46, causing
equal and opposite voltages to appear at the
anode I41 and cathode I48. The clipper output
consists solely of the aperture pulse and the su
perimposed echo occurring during the aperture
pulse. From one point of view, the aperture pulse
sistor I33, can be made just short of the amount
required to hold the range-delay at any position.
Heretofore we have considered the effect of the
delayed range voltage and the aperture pulse
which is symmetrically positioned with reference
to the trailing edge of the range delay voltage,
1. e.,'half of the aperture pulse appears on each
side of the trailing edge of the delayed range volt
age. Any signal, half of which appeared on either
side of the trailing edge of the delayed range
voltage would have no effect on the potential of
terminal I53 or the resulting bias on the grid
94 'since this signal would not change the A.-C.
axis of the voltage across the diodes I49 and I50.
However, if the signal is displaced to one side of
can be considered as a gate which isopened to
let the coincident echo through. In the mixer
and clipper, the echoes bracketed by'the aperture
7 pulse are segregated from the other'signals. The
output of the clipper I43 is also fed to train and
elevation tracking circuits [436. which sweep the
antenna pointed at the target having an echo
bracketed by the aperture pulse.
,
The voltages at the anode I41 and cathode I48
are fed through series connected diodes I49 and
I50. The diodes are shunted by a resistance I5I
having a slider I52 connected to ground; Since
the voltages applied to the diodes are equal and
opposite, it is obvious that the slider I52 can be
adjusted to a position such that the potential of
the terminal I53 between the diodes will be inde
the trailing edge of the delayed range voltage, the
' terminal I53 is driven in the negative direction
if the greater part of the signal is within the de
layed-range voltage or more positive if the greater
part of thesignal is outside (beyond the trailing
edge’ of ) the delayed range voltage. This can be
' explained by considering the echo signal and ap
erture pulse voltage from the inverter I46 as
pendent of the amplitudes of thesap‘erturepulse
or the received signals. Under this condition, the
condensers I5Ia and I5Ib maintain an average
voltages of opposite sign applied to the terminal
potential such that the diodes I49, I50 Iconduct
missible'beca-use the current through the diodes
I 53. with 'the delayed range voltage; This is per
only during the peaks of the aperture pulse. ' The “
terminal I53 is connected to a‘slider. I54 on the
resistance I33 which applies. a desired fraction
of the delayed range voltage appearing across the
resistance I33. If the range of the aperture pulse
were exactly 50% of the average interval be
is due to the difference between the delayed range
and signal voltages. Part of the signal voltages
from the inverter consists of the aperture pulse
voltages which are symmetrically (or at least
?xedly) positioned with respect to the trailing
edge of the delayed range voltage. Since these
tween transmitted pulses, the delayed range volt
aperture pulse voltages subtract equal amounts
age applied to the terminal I 53 would be a sym
metrical square wavev having its A.-C. axis mid
from the voltage at the terminal I53 on opposite
sides of the trailing edge of the delayed range
voltage, it is apparent that the aperture pulse
does not change the bias on the grid 94. If the
echo signal were similarly located with reference
to the trailing edge of the delayed range voltage,
it likewise would have no effect upon the bias of
the grid.94.. If the echo signal were positioned
way between the positiveand negative peaks.
During that part of the aperture pulse occurring
during the positive peak of the delayed range
voltage, less current would flow through the di~
ode I49 and more current would ?ow ‘through
the diode I50. During that part of the aperture
pulse occurring during the negative peakof the "
delayed range voltage, more current would flow
through the diode I49 and‘ less current ‘would
?ow through the diode I 50. Because the positive
and negative Peaks of the delayed range voltage
wholly'withln the trailing edge of the delayed
range voltage, the echo signal would subtract
7 from the positive peak of the delayed range volt
age and would tend to lower the unidirectional
575
voltage at the terminal 153. This, in turn, would
2,595,876:
11
cause a more negative bias to be applied to the
grid 94 and would shorten the range delay of the
multivibrator 83, 84, thus moving the trailing edge
of the delayed range voltage toward the echo sig
nal. The opposite effect would be obtained if the
echo signal were beyond the trailing edge of the
delayed range voltage. The action of the range
tracking circuit accordingly tends to maintain the
echo signal centered with respect to the trailing
edge of the delayed range voltage. In order that
the range tracking circuit may be stable it is
adjusted so that the bias for the grid 94 from the
delayed range voltage is just short of the amount
required to adjust the delay interval of the multi
vibrator 83, 84 to coincidence with the range de
lay. Because of this the echo signal, which is re
lied upon to supply the additional bias for the
,
,
,
12
.
.
.
voltage, as represented in lines (I and G, equal
amounts would be subtracted irom the delayed
range voltage on opposite sides of its trailing edge
and the A.-C. axis of the combined voltage would
be unchangedyand would be independent of the
magnitude of the aperture pulse. If the aper
ture pulse is not symmetrically located with re
spect to the trailing edge of the delayed range
voltage, it will have a negative (or positive) effect
on the A.-C. axis of the combined voltage de
pendent upon whether the greater part of the
aperture pulse is to the left (or right) of the
trailing edge ,of the delayed range voltage. For
any particular equipment, the effect of the aper
ture pulse will be constant and the resultant
feed-back bias for the grid 94 can be adjusted
so as to be just short of that required to hold
thedelayed range voltage constant. Since the
effect of the delayed range voltage and aperture
respect to the trailing edge of the delayed range
voltage but will be positioned beyond the trailing 20 pulse is constant, the echo which varies with the
target range will tend to shift with respect to
edge of the delayed range voltage by an amount
the trailing edge of the delayed range voltage.
necessary to supply the addition-a1 bias of the grid
grid 94, will not be symmetrically positioned with
The echo voltage, being mixed in the circuit of the
94. This error can be made very small indeed,
diodes I49, I50 in a negative sense with respect to
since only a very small additional bias is required
to cause the range delay to adjust itself to follow 25 the delayed range voltage, has a negative eifect
grams on a common scale, in which line A rep
on the feed-back bias of the grid 94 tending to
decrease the range delay if the greater part of
the echo voltage is to the left of the trailing edge
of the delayed range voltage and has an opposite
, pulse which is shifted into coincidence with the
range voltage accordingly supplies a range track—
the signal.
The operation of the automatic range tracking
circuit is illustrated in Fig. 2,, a series of dia
resentsthe transmitted pulses, line D represents 30 e?ect if vthe greater part of the echo voltage is
to the right of the trailing edge of the delayed
the receiver output which includes the trans
range voltage. The position of the echo voltage
mitted pulses, echoes from remote objects and
with respect to the trailing edge of the delayed
noise voltages, line C‘ represents the aperture
echo from the target the operator wishes to fol 35 ing voltage tending to adjust the delay of the
multivibrator 83, 84 to correspondence with the
low, line B represents the output of the range
range of the target.’
delay multivibrator 83, 84, and lines E and F rep
Instead of using the delayed range voltage from
resent the output of the inverter I46 which com
the slider I54 to supply the greater part of the
prises the mixed aperture pulse and target echo.
feed-back bias for the range delay multivibrator
As indicated in line B, ‘the range delay voltage is
83, 84, it is possible to obtain similar results by
a square wave voltage having a slightly sloped
utilizing a portion of the range delay voltage ap
trailing edge which can be shifted throughout
pearing in the plate resistor 86. This is accom
the greater part of the interval between trans
plishediby opening a switch I55 in the lead to the
mitted pulses. The aperture pulse C, being syn
chronized at the intersection of the line I51 with 45 slider I54 and closing the switch on a. contact I56
connected to a slider I51 on the plate resistor 86.
the range delay voltage, has a de?nite time phase
When the switch IOI is in the automatic track
with respect to the trailing end of the range delay
ing position, i. e., closed on the contact I26, a
voltage; i. e., it begins as the trailing end of wave
portion of the range delay voltage determined
B starts. The important feature of the aperture
pulse is that it brackets the trailing edge of the 50 by the setting of the slider I51 is fed to the ter
minal I53. Because the range delay voltage is
delayed range voltage shown in line G. The
delayed range voltage is a square wave voltage
takendirectly from ‘the plate resistor 86, it has a
having leading and trailing edges shifted with
sloping trailing edge as indicated in line B of
respect to the range delay voltage which might
Fig. 2 of a width comparable to the width of the
more accurately be termed a “delayed range
aperture pulse. At the terminal I53 the range
delay voltage.” The peak magnitude of the de
delay voltage from the slider I5‘! is roughly equiv
layed range voltage is less than the peak mag
alent to a square wave voltage such as the wave
nitudes of the inverter output, lines E and F‘, and
G which has its trailing edge half way down the
in typical equipment may be from 1/10 to 1Arc of
slope of the range delay voltage. The voltage
the peaks of the inverter output.
from the slider I51 is therefore approximately
The delayed range voltage creates a feed-back
equivalent to the delayed range voltage from the
bias on the grid 94 just short of that required
slider I54 shown in line G of Fig. 2. Since the
slope of the trailing edge of the range delay volt
to hold the range delay constant. Because of
its time phase, the aperture pulse has a constant
age is not easily adjustable, it will in general be
e?ect upon the feed-back bias which is dependent 55 more convenient to use the equivalent delayed
upon the asymmetry of the aperture pulse with
range voltage shown in line G of Fig. 2, the
respect to the trailing edge of the delayed range
trailing edge of which can be more easily con
voltage. This is due to the fact that in the cir
trolled by varying the electrical length of the
cuit including the diodes I49, I50, the aperture
transmission line I32.
pulse is mixed in a negative sense with the 70
What I claim as new and desire to secure by
delayed range voltage to produce a feed-back
Letters Patent of the United States is:
bias for the grid 94 proportional to the position
1. In locating equipment of the type wherein
of the A.-C. axis of the combined voltage. If
recurrent energy pulses are transmitted and the
the aperture pulse were equally spaced on oppo
range of remote objects is determined from the
site sides of the trailing edge of the delayed range 75 time intervals required for corresponding re?ected
2,595,876
14
pulses to return therefrom,
13 means for transmit
with respect to said alternating current axis to
ting pulses of wave energy at an instantaneously
vary the delay of said second means in the di
varying but constant average rate, a range delay
multivibrator synchronized by the transmitted
pulses and having a delay adjustable to coinci
dence with re?ected pulses from a remote object
rection to bring said interval into symmetry with
said termination of said delayed range pulse.
5
5. The method of determining the distance of
remote objects from a predetermined point in
space, comprising the steps of transmitting suc
having a particular range, a bridge circuit includ
ing a condenser and a potentiometer for balancing
cessive energy pulses, receiving corresponding
the condenser voltage, means to charge said con
energy pulses from said remote objects, visually
denser to a voltage determined by the range delay 10 indicating each of said received pulses in space
position corresponding to the time of arrival
interval, a modulator for producing an alter
nating voltage having alternate peaks propor
thereof after the corresponding transmitted pulse,
and continuously and cyclically varying the repe
tional to said condenser and said potentiometer
Voltage, and means responsive to said alternating
tition rate of said transmitted pulses in a gradual
voltage for adjusting said potentiometer in the 15 manner to reduce the effect of interfering re
ceived pulses.
direction to reduce said voltage whereby the po
6. In locating equipment, means to transmit
tentiometer adjustment corresponds to the par
ticular range of said remote object as a per
centage of the average interval between trans
mitted pulses.
recurrent energy pulses, means to receive corre
sponding returned pulses from remote objects,
20 range indicating means synchronized with said
transmitting means and responsive to the times
2. In locating equipment, means for transmit
of receipt of said corresponding pulses with re
ting pulses of wave energy at a variable repetition
spect to said transmitted pulses, said indicating
rate, means for receiving echoes of the transmit
ted pulses, means for segregating echoes arriving
means being sensitive to the accumulation of re
during intervals at a predetermined time delay 25 ceived pulses having substantially equal time de
lays after the respective transmitted pulses, means
measured from said transmitted pulses, means
generating a square wave voltage having a width
to vary the repetition rate of said transmitted
pulses uniformly in accordance with a triangular
varying with said delay and having an edge oc
curring during said intervals‘, and means respon
characteristic, and means to maintain said indi
sive to the time phase of said segregated echoes 30 cating means continuously synchronized with said
transmitted pulses during the variations in said
with respect to said edge of the square Wave volt
repetition rate, thereby to reduce the response of
age for adjusting the delay of said segregating
means so as to hold said edge in a ?xed time
‘ said indicating means to pulses received from re
mote objects beyond a predetermined distance
phase with respect to said echoes.
3. In locating equipment having means for 35 from said equipment.
'7. In high frequency pulse locating equipment,
transmitting pulses of wave energy and means
means for transmitting pulses of high frequency
vfor receiving echoes of the transmitted pulses, a
energy at a substantially constant average pulse
tracking circuit for following a particular target
repetition frequency, means for receiving re?ected
comprising, means for generating a square wave
range delayr voltage having a width varying with it pulses from remote objects, oscillographic indicat
ing means for visually indicating the range of
range, means for mixing said range delay voltage
remote objects as a function of the time interval
with signal voltages occurring during an interval
between transmission of a pulse and reception
including the time of an edge of said range delay
voltage in a manner such that the area of the
mixed voltage on one side of its alternating cur
rent axis during said interval is affected in op
posite sense by signal voltages on opposite sides
of said edge, means responsive to the difference
between resultant areas preceding and following
said edge for varying the width of the range delay
voltage in the direction to bring the position of
said target echo to coincidence with said edge of
the range delay voltage.
'
'
of a corresponding re?ected pulse, means for
continuously and cyclically and in a gradual man
ner frequency-modulating the repetition rate of
said transmitted pulses about said average fre
quency, and means for continuously maintaining
said indicating means in synchronism with said
transmitting means, thereby to reduce the effect
of undesired re?ected pulses from objects at
ranges corresponding to time intervals greater
than the time interval between transmitted pulses
4. In a remote object detecting equipment of ' at said average frequency.
the type wherein recurrent energy pulses are‘ 55
8. The method of determining the distance of‘
remote objects relative to a predetermined point
transmitted and the time interval required for
corresponding energy pulses to .return from re
in space, comprising the steps of generating oscil
mote objects is measured to determine the dis
lations having a substantially constant frequency,
tance to such objects, means for transmitting
transmitting an energy pulse once for each cycle
energy pulses at an instantaneously varying but 60 of said oscillations, receiving energy pulses re
constant average rate, means to produce a de
?ected from remote objects at time intervals
layed range pulse, means to synchronize the'in
corresponding to their distances, visually display
itiation of said delayed range pulse with said
ing each of said received pulses in space position
transmitted pulses, means to adjust the termina
as a function of their distance from said point,
tion of said delayed range pulse to coincidence
and continuously varying the phase position of
with pulses received from remote objects having
the transmitted pulses with respect to the cycle
a particular distance, means for receiving pulses
of said oscillations in accordance with a double
from remote objects during an interval including
parabolic wave having a shape substantially cor
said termination, means for mixing pulses re
responding to that of a doubly-integrated square
ceived from remote objects during said interval
wave, thereby to cause any re?ecting object at a
with said delayed range pulse to produce a re
‘distance corresponding to a time interval less
sultant voltage having an alternating current axis
than a cycle of said oscillations to produce a sharp
dependent on the coincidence of the received
image over a relatively small area and to cause
pulses with respect to said termination, and means
any re?ecting objects exceeding said distance to
utilizing the asymmetry of said resultant voltage 75 produce illumination of substantially constant,
2,595,876
15
lower intensity over a substantially greater area.
9. In a remote object detecting system, means
to transmit recurrent energy pulses at a constant
average repetition rate, means to receive said
pulses as returned from remote objects, oscillo
16'
13. In combination, a transmission line having
one end short-circuited and the other end termi
nated in its characteristic impedance, means to
apply an abrupt current change to the terminated
end of said line, thereby to produce a voltage pulse
at said terminated end due to re?ection in said
graphic means visually to display said received
line, and means to delay said current change by
pulses in space position corresponding to the time
a time interval corresponding to the electrical
of arrival thereof after the next preceding trans
length of said line, an impedance terminating
mitted pulse, means continuously and cyclically
to vary the repetition rate of said transmitted 10 said last means, thereby to produce across said
last impedance a voltage change having an edge
pulses in a gradual manner, means to maintain
bracketed in time by said voltage pulse produced
said oscillographic means continuously synchro
by said transmission line.
nized with said transmitted pulses during the
14. In combination, a ?rst transmission line
variations in said repetition rate, thereby visually
having one end short-circuited and the other end
to display only pulses from remote objects within
terminated in its characteristic impedance, a seca predetermined distance from said system, and
ond transmission line having an input end and
an end terminated in its characteristic impedance,
pulses from a particular remote object, said last
said second line having an electrical length sub
means being responsive to the average propor
tion of the interval between successive trans 20 stantially equal to the electrical length of said
?rst line, means to apply an abrupt current
mitted pulses occupied by the travel thereof to
change simultaneously to the terminated end of
and from said object.
.
the ?rst line and the input end of said second
10. In combination, a source of voltage havingr
line, thereby to produce an abrupt voltage change
an abrupt change in value at a predetermined in
stant of time, a source of voltage having a. con 25 across said last impedance bracketed in time by
a voltage pulse produced by said current change
stant value with a voltage pulse superimposed
at the terminated end of said ?rst line.
thereon, an energy storage device, means to
15. In locating equipment of the type wherein
charge said device in one direction for a prede
recurrent energy pulses are transmitted and dis
termined period of time before said abrupt
change and at a rate determined by the total 30 tances to remote objects are determined from the
time intervals required for corresponding pulses
voltage of said sources, and means to charge said
to return therefrom, a recurrent wave generator
device in the opposite direction for a predeter
means to measure the time delay of said received
mined time after said abrupt change and at a
for determining the average recurrence rate of
rate determined by the total voltage of said ?rst
pulse transmission, a delay multivibrator syn
the voltage of said second source, thereby to pro
current triggering pulses of controllable width, a
pulse transmitter synchronized by said multivi
brator for transmitting said energy pulses in
synchronism with the trailing edges of said trig
gering pulses, a second generator of periodic waves
source and a reverse voltage of value equal to 35 chronized by said generator for generating re
duce a total charge on said storage device of
value determined by the timing of said voltage
pulse with respect to said predetermined instant
40
of time.
of predetermined wave form and relatively low
11. In combination, a source of voltage pro
recurrence rate, means for continuously and
ducing a cyclic voltage wave with one constant
cyclically width-modulating said multivibrator in
value before a predetermined phase point in the
response to said periodic waves, thereby to pro
cycle thereof and another constant value after
said predetermined phase point, a source of volt 45 duce a corresponding modulation in said trigger
ing pulse widths and in said rate of pulse trans
age pulses of recurrence rate corresponding to the
mission, and means synchronized with the pulses
frequency of said cyclic voltage Wave, an energy
from said transmitter for receiving and indicat
storage device, means to charge said device in
ing said corresponding returned pulses as a func
one direction for a short period of time before
tion of said time intervals, thus to avoid false
said predetermined phase point in said cycle and
measurements due to objects more remote from
at a rate determined by the total voltage of said
said equipment than the distance corresponding
sources, and means to charge said device in the
to the time interval~between successive trans
opposite direction for a second short period of
mitted pulses.
time at a rate determined by the sum of the volt
16. In a system for measuring and indicating
age of said ?rst source and a reverse voltage of
the average width of recurrent electrical pulses,
value equal to the voltage of said second source,
means for developing a unidirectional control po
thereby to produce a charge on said device de
tential proportional to the average width of said
pendent on the relative phase position of said
pulses, an adjustable source of unidirectional
pulses with respect to said predetermined phase
point.
60 reference potential, a source of alternating refer
ence voltage of predetermined frequency, means
for producing an alternating error voltage of the
age pulses having a point of neutral potential,
same frequency whose amplitude and polarity
two recti?ers in series connected across said
with respect to said reference voltage are con
source, said recti?ers being poled to conduct cur
rent when said pulses take place, a source of cyclic 65 trolled respectively by the sign and magnitude of
voltage of frequency equal to the frequency of
the potential difference between said unidirec
said pulses and having an abrupt change in value
tional potentials, a directional motor controlled
at a predetermined phase point in the cycle
by said error voltage for adjusting said reference
potential in a sense to decrease said potential
thereof, a capacitor, means connecting said last
source and said capacitor in series between said 70 difference, and an indicating means controlled
point of neutral potential and the common con
by said motor.
17. In a system for remotely indicating the
nection of said recti?ers, thereby to produce a
charge on said capacitor determined by the phase
average width of recurrent electrical pulses, means
for developing a unidirectional control potential
position of said pulses with respect to said prede
75 proportional to the average width of said pulses,
termined phase point.
12. In combination, a source of periodic volt
2,596,876
17
means comprising a potentiometer having a mov
able contact arm for developing an adjustable
unidirectional reference potential, a source of al
ternating reference voltage of predetermined fre
18
trigger pulse, means for supplying each of said
echo pulses to said device to produce an indica
tion on said coordinate and at a space position
dependent upon the elapsed time between said
quency, means for producing an alternating error 5 echo pulse and its corresponding transmitted
voltage of the same frequency whose amplitude
pulse, and means for smoothly and cyclically
and polarity with respect to said reference voltage
varying the repetition rate of said transmitted
are controlled respectively by the sign and magni
pulses, whereby indications of echoes received
tude of the potential difference between said uni
prior to the transmission of a succeeding trans
directional potentials, an alternating current 10 mitted pulse tend to be superimposed while indi
motor energized from said voltages, the direction
cations of later echoes tend to be scattered;
and extent of rotation of the motor rotor being
20. Apparatus for determining the distance of
dependent on the amplitude and polarity of said
remote objects from a predetermined point in
error voltage, means controlled by said rotor for
space, comprisingmeans for transmitting, suc
adjusting the position of said contact arm in a 15 cessive energy pulses, means for receiving corre
sense to decrease said potential difference, and
sponding energy pulses from said remote ‘objects,
a remote indicating means controlled by saidrotor
means for visually indicating each of said re
for indicating the position of said arm on said
ceived pulses in space position corresponding to
potentiometer.
the time of arrival thereof after the correspond
18. In locating equipment of the type wherein 20 ing transmitted pulses, and electronic means for
recurrent energy pulses are transmitted and the
smoothly and cyclically varying the repetition
positions of remote objects are determined from
rate of said transmitted pulses in a predetermined
the time intervals required for corresponding
manner to minimize the effect of interfering re
pulses to return therefrom, a pulse transmitter,
ceived pulses.
l.‘
control means generating synchronizing pulses at 25
DONALD E. NORGAARD.
constant rate, a variable time delay means inter
posed between said control means and said trans
REFERENCES CITED
mitter, means for continuously and cyclically
varying said delay means in a predetermined
manner to modulate the frequency of pulse trans 30
mission, and means synchronized with the pulses
The following references are of record: in the
?le of this patent:
UNITED STATES PATENTS
from said transmitter for receiving and indicating
said corresponding returned pulses as a function
of said time intervals, thereby to avoid false in
dications due to pulses returned from objects 35
more remote from said equipment than the dis
tance corresponding to said time intervals.
19. In pulse echo ‘locating equipment, means
'
Number
Name
,
Date
1,979,225
Hart ____________ __ Oct. 30, 1934
2,189,549
Hershberger ____-____ Feb. 6, 1940
2,227,598
2,266,401
Lyman et a1. ______ __ Jan. 7, 1941
Reeves __________ __ Dec. 16, 1941
2,308,752
Had?eld _________ __ Jan. 19, 1943
2,309,525
Mohr _____________ Jan. 26, 1943
means for receiving echoes of said pulses from 40 2,328,944
remote objects, an oscillographic display device
2,408,692
including sweep circuit means and arranged to
2,415,095
produce a range indication coordinate controlled
2,419,292
Beatty ___________ __ Sept. 7, 1943
for transmitting a train of pulses of wave energy,
Shore ____________ __ Oct. 1, 1946
Varian ___________ __ Feb. 4, 1947
Shepard _________ __ Apr. 22, 1947
by said circuit means, means for producing a
2,419,541 _
DevRosa _________ __ Apr. 29, 1947
train of trigger pulses each said pulse synchro
2,425,600
2,433,343
2,444,452
2,448,016
Coykendall ______ __ Aug. 12.
Chatterjea _______ __ Dec. 30,
Labin ____________ __ July 6,
Busignies ________ .. Aug. 31,
2,452,598
Page _____..____..____ Nov. 2, 1948
2,485,583
Ginzton _______ _'_-_ Oct. 25, 1949
nized with a corresponding transmitted pulse, a
pulse generator controlled by said trigger pulses
and connected to energize said sweep circuit
means with a single range sweep pulse of prede
termined waveform in response to each applied 50
1947
1947
1948
1948