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Патент USA US2412669

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Dec, 17, 1946. `
- A. V. BEDFORD
2,412,669
PULSE-ECHO POSITION INDICATOR
Filed June 1_9, 1942
NN
‘ 2 Sheets--Sheet l
Dec. 17, 1946.
A. v. BEDFORD
PULSE-ECHO POSITION INDICATOR
_
Filed June 19, 1942
2,412,669 `
Patented Dec. 17, 1946
2,412,669
unirse >
2,412,669
PULSE-nono POSITION mDIcA'roR
Alda V. Bedford, Collingswood, N. J., assignor to
Radio Corporation of. America, a- corporation
of Delaware
Application June 19, 1942, Serial No. 447,630
5 Claims. (Cl. 250,-1)
My invention relates to pulse-echo position in-V
dicating systems and particularly to systems
adapted to convey the position information to a
remote point or central station. The invention
is- hereinafter described as applied to a position
indication system in which a directive transmit
ting antenna is rotated horizontally to sweep a
radio beam through a horizontal plane while puls
ing the beam. The radio pulse is reflected if
it strikes an airplane or the like. The reiiected
pulse is picked up by a receiver located near the
pulse transmitter and the distance of the re
'a
rates being 30 per second and 600 per second,`
respectively, in the example described below.
The `signal for pulsing or modulating the cathode
ray of the indicator tube at the remote sta
tion (this signal corresponding to the reflected
pulses applied to the indicator tube at the trans
mitter) is obtained by applying the >received re
flected pulses to a second cathode ray tube at
the transmitter to store them on a fluorescent
screen and by deflecting the cathode ray of this
tube circularly at the pulse rate. The result
ing stored pulse at a point on the circular trace
is scanned _by a single aperture disc rotating at
flecting object is determined by the time elapsed
the low-frequency radial-deflection rate employed
between transmission and reception of the pulse._
The direction of the reflecting object is deter 15 at the remote indicator tube. When the scan
ning disc aperture comes opposite the light spot
mined also by employing at the receiver a_ cath
on the circular trace, a pulse of light is trans
ode ray indicator tube in `,which the cathode ray
mitted to a photoelectric cell to produce a cor- .
is rotated in synchronism with the rotation of
responding electrical pulse. These pulses may be
the transmitting antenna and is swept radially
20 transmitted over an ordinary wire line to the cath
ode ray tube indicator at the remote station since
It may be desirable to install a plurality of
their repetitionrrate in the example assumed is
stations of the above-described type spaced apart
30 per second instead of 600 per second as at
the proper distance to give protection over a
the transmitter station with a corresponding re
large geographical area. In that case it may
be desirable to convey the information from all 25 duction in the frequency band.'
In another embodiment of the invention, the
pulse-echo stations to a central station where
frequency reduction is obtained by employing a
one person has before him a view of all the posi
to establish a distance coordinate. -
tion-indicating views or patterns that are present ` ' cathode ray storage tube in place of the scan
ning disc and by scanning circularly the storage
at the individual stations. A diñiculty in doing
this is that such information ordinarily occupies 30 tube. The pulse signal is stored on a mosaic by '
a fairly wide frequency band, from 600 to 60,000
cycles per second, for example. 'I'his band is
too wide for transmission over the usual tele
phone,`telegraph or other wire line.
An object of the present invention is to pro 35
means of a cathode ray that is deflected at the
high-frequency rate,v such as 600 per second. It is
taken oiï the mosaic by means of a cathode ray
that is deiiected at the low-frequency rate, such
as 30 per second.
The invention will> be better understood from
the following description taken in connection
with the accompanying drawings in which Fig. 1
enough to permit transmission of the position
is a diagram of a pulse-echo position indicator
indication information over a wire line to a cen
40 system embodying the invention, and Fig. 2 is a
tral station.
.
di-agram of another embodiment of the inven
Another object of the invention is to provide an
vide a method of and means for reducing the
above-mentioned frequency band, preferably
improved method of and means for conveying
information from a radio pulse-echo position in
tion. Like parts in the two figures are indicated
_by similar reference numerals.
.
Referring to Fig. 1, a radio transmitter I0 is
"Another object of my invention is to reduce 45 keyed at the rate ,of 600 pulses per second, for
the amplitude of the noise in the signal of reduced . example, to radiate pulses of very short dura
frequency as compared with the original signal.
tion from a suitable directive antenna II. An
tenna Il may be la dipole in a parabolic reflector
In one embodiment of my invention the posi
I2 or it may be of any other suitable design. It
tlon indication at .the remote station appears
on a cathode ray tube provided with a deflecting
is rotated at 10 rotations per minute, for example,
in a horizontal plane about a vertical shaft I3.
yoke that is rotated in synchronism with the
The shaft I3 is- driven by a synchronous motor
rotation of the transmitter antenna. ' The radial
ldeflection produced by this yoke is at a lowy fre
I4 through a gear box I6, the mechanical cou
dicator to a remote point.
quency rate as compared with the rate at the
pling being indicated by the broken lines. The
indicator tube .located at> thetransmltter; these 55 ' motor i4 is connected to a (iO-cycle power line
2,412,669
4
I5. Suitable pulse-keying means I1 is driven 4by
a synchronizing-pulse generator I8.
The receiver I6, which is located in the vicinity
of the transmitter, responds to the reflected pulses
of carrier-wave frequency, demodulates them,
and applies them to the control electrode of a
cathode-ray indicator tube 2| having a fluores
cent screen 22. Tube 2| is provided with a rotat
.
circular deflection. In order to direct light from
the spot 35‘ to a photoelectric cell 43, two mirrors
44 and 46 are mounted on the disc 42, one opposite
the disc aperture and the other at the disc axis.
A lens system 41 in front of the disc aperture
images the light spot 35 thereon. Counterbal
ancing means for the disc is shown at 40. The
disc 42 is> rotated at a comparatively low speed.
able dei'lecting yoke 23 of the magnetic type
which may be a submultiple ofthe pulse rate.
havingfslip rings 24 and 26 which are connected 10 this being 30 rotations per second in the example
through brushes to a. sawtooth generator 2l. The
illustrated whereby the frequency band is reduced
yoke 23 is rotated synchronously with the antenna
to 3%00 or 1750 of the original band width. It may
rotation by means of gears 28 and 29 mechani
be driven through a gear box 5| by the syn
cally coupled to the gear box I8.
chronous motor I4. The pulse output of the
’
The sawtooth generator 21 is synchronized with 15 photoelectric cell 43 is amplified by an amplifier
the radio-pulse transmission by means of pulses
52 and transmitted over a wireline to the central
from the synchronizing generator _| 8 supplied
station.
_
over a conductor 3|. T_he deiìecting wave ap-~
plied to the yoke 23 contains a direct current com
At the central station there is a cathode ray
indicator tube 54 which, like the tube 2|, is pro
ponent such that the deflection of the cathode ray 20 vided with a rotatable deñecting yoke 56 that is
is from the center of screen 22 toward the circum
rotated in synchronism with the antenna rotation.
ference. Since the cathode-ray tube 2| is biased
This may be done by a synchronous motor 51 that
is supplied with power from the same 60 cycle
to beam-current cutod in the absence of a re
ceived pulse, or at least to less than maximum
line l5 that supplies power to the motor |4. A
beam current, a luminous 'spot appears on the 25 sawtooth deñecting wave recurring 30 times per
screen 22 upon the reception of a pulse. This
second is produced in the yoke 56 by a sawtooth.
spot has a circumferential position depending
Wave generator 6| to deñect the cathode beam
radially. The generator 6| is held in fixed time
relation to the pulse transmission by connecting
position (distance from center of screen) depend 30 lit to the 60-cycle power line I6 through a phase
l upon the direction of the reflecting object from the
rotating 'transmitter antenna and has a radial
ing upon the distance of said object from the
transmitter antenna.
shifter 62. It will be understood' that at the in
dicator tubes 2| and 54 the sawtcoth sweep is so
If an attempt were made to transmit the re
phased with respect to the transmitter pulse that
iiected pulse, which recurs at 600 timesV per sec
the deflection starts from the center of the
ond, to a remote station over an ordinary wire 35 iiuorescent screen at the instant the pulse is
line it would be found that the fidelity of trans
transmitted. The fluorescent screen of the tube
mission would be very poor as the telephone line
54 is indicated at 63.'
« would not transmit the required frequency band.
The persistence of fluorescence of the screen 68 '
Therefore, I have provided means for reducing.
and the screen 22 of tube 2i should be several
the frequency. band required whereby informa 40 seconds, preferably six seconds' where the yoke
tion sent over a telephone line to a central station
will give on the indicator tube an acceptable in
dication of the position of the airplane or other
rotates 10 R. P. M. or once in 6 seconds. The
persistence of fluorescence of the screen 30 of the
tube 32 should be at least 1,600 second (the time of
one circular deflection) and preferably is about
The frequency-band reducing means comprises 45 ¿so second in the example shown for good signal
a cathode ray tube 32 having a fluorescent screen
to noise ratio. The iiuorescence decays gradually,
8U. Circular deñection of the cathode ray is
as is well known, but a satisfactory screenA is one
provided by means of two pairs of deiiecting coils
in which the light falls to one-half maximum in
33 and 34 positioned at right angles to each other.
tensity in 1%@ second.
reiiecting object.
Coils 33 and 34 are supplied, from a suitable 50
From the foregoing it Will be apparent that the '
source 36, with sine wave current having a fre
pulse produced in the photoelectric cell 43 occurs
qency of 600 cycles per second, the current in
at a time following the instant of pulse trans
coils 34 being shifted 90 degrees with respect to
mission which is measured by time taken for the
that in coils 33, by means of a phase shifter 3l.
disc aperture to rotate from the “O-delay” posi
The GOO-cycle sine wave current is synchronous 55 tion indicated on the screen 30 to the position of
with the keying pulses. In the example shown
it is produced by supplying the 60G-cycle pulses
from the synchronizing pulse generator I8 over
the spot of light 35.` 'I'hus the 30-cycle pulses
sent over the wire line to the central station have
a time delay with respect to the instant of pulse
a conductor 38 to the sine-wave source 36. The
transmission that corresponds accurately to the
source A36 may be simply a circuit tuned to 600 60 delay between pulse transmission and pulse re
cycles per second. The tuned circuit converts the
ception at receiver I9. `'I'he radial position in
pulses into sine waves which may be amplified or
dication on' the indicator >tube 54 will be the
the pulses may be amplified before conversion. '
same as on the indicator tube 2|.
'I‘he tube 32 may be (but is not necessarily)
In Fig. 2 the frequency band reduction is ob
biased to beam cutoff so that a spot of light 35 65 tained by means of a cathode-ray storage tube
appears on -the screen 30 whenv a reflected pulse
66 of the general type shown in Schroter Patent
is applied to the control electrode of tube 32 over
2,175,573, issued October 10. 1939. The specific
a conductor 4|. This light spot appears at a
tube construction illustrated- is the same as‘that
point on the path of circular deflection indicated
shown in Beers Patent 2,273,172, issued February
by the dotted circular trace and at a position 70 17, 1942.- The tube 66 is a double-tube construc- .
determined by the time that the reíiected pulse
tion in which a-highly evacuated envelope con
appears upon the control electrode.
tains oppositely-disposed electron guns, each of
A rotatable disc 42 having a single aperture
which may be of conventional construction in
which preferably is a radial slit is located opposite
cluding the usual cathode control electrode, ñrst
the screen 30, and centered with respect t0 thel 75 Vanode and second anode.
'
asiaeco , _
mosaic lindicated at 1l and collecting electrodes
transmission which time> depends upon the po
sition of the stored pulse on the mosaic li.
yringswhereby they may collect secondary elec
trons from the mosaic 1| without being struck
the ray is unblocked or modulated to produce a
yspot of light at a distance from said center which
‘.The tube includes the so-called double-sided
12 and 3 on opposite sides thereof. The collect
ing electrodes 12 and 18 may be in the form of
by the electron beams as the mosaic is-scanned.
Therefore, as the cathode ray oi’ tube dt is de
ilected outwardly from the center or screen B3.
"represents ‘the distance of the reflecting airplane
several well-known constructions. For example,
or the like from the rotating antenna Il. The
direction of the reflecting object from the an
28, 1934, in the name of Leslie E.' Flory and as
Fig. 1.v
The double-sided mosaic screen 1i may be any of
it may be constructed in accordance with the 10 tenna Il -is shown by the circumferential posi
_tion ofthe lightspot Just as in the system of
teachings 'of Patent No. 2 045.984, filed February
.
It may be noted that, in addition to reducing
the frequency band, the use of my invention lm
- Preferably the mosaic 1| is operated slightly
positive with respect to the second anode. In the 15 proves the signal to noise ratio since the reflect
ed pulses occur and are stored in a deñnite phase
example illustrated. the mosaic is connected to
relation whereas noise pulses occur in a random
ground while the second anodes are 25 volts nega
time relation.
tive and the other electron gun electrodes are op
I claim ’as my invention:
v „
erated at suitable negative potentials with re
1. In a radio system, means for transmitting
spect to ground, as indicated. Specific voltages
pulses to an object whereby they are reflected
are given on the drawings merely by way of ex
from said object, said pulses recurring at a cer
ample.
tain rate, means for receiving said reflected
The cathode ray in the left hand section of
pulses in the region of the transmitting means,
tube 56 is deflected along a line on the mosaic 1I
signed to Radio Corporation of America.
at the rate of 600 deñections per second by means
there being a certain time interval between the
instant of transmission _of a pulse and the re
ception of said pulse, means for converting said
reflected pulses to pulses which recur at a sub
multiple frequency of said certain rate with each
line on the mosaic at the rate of 30 deñections
per second by means of deñecting coils 18 con 30 pulse of said submultiple frequency occurring at
nected to a sawtooth generator 19 which may be
a certain time interval following a time reference
synchronized from the power line l5.
^
instant, said last-mentioned time interval being
' 'I'he collecting electrode 12, which may be con
equal to said submultiple times said first-men
nected to ground through a resistor 1d, functions
_ tioned time interval, a cathode ray indicator tube
as the input control electrode and is connected to
having a'beam control element, means for ap
the output circuit of 4the receiver I9 through a
plying said submultiple pulses to said control ele
conductor 10. The collector electrode 13, which
ment, and means for deilecting the cathode ray
may be connected to ground through a resistor
of said indicator tube at said submultiple fre
18, functions as the signal output electrode to
quency with the start of each deflection begin
supply the signal of reduced band width to the 40 ning at said time reference instant.
wireline through an ampliñer 15.
2. In a radio system, means for transmitting
The operation of the- delay tube SS is substan
pulses to an object whereby they are reñected `
tially as follows: Simultaneously with the scan
from said object, said pulses recurring at a cer-'
ning of the mosaic 1_l by the electron beam_ ro
tain
rate, means `for receiving said reflected
45
duced in the left hand portion of the tube` the
pulses
in the region of the transmitting means,
received reflected pulse is supplied over the con
there being a certain time interval between said ,
ductor -10 and is impressed upon the electrode 12
transmission and reception, a cathode ray tube
to vary its potential in accordance with said pulse
having a storage screen and means for directing
whereby the individual capacity elements of the
a
mosaic acquire electrostatic charges in accord 50 cathode ray against said screen, means for de
flecting the cathode ray along said screen at said
ance with the amplitude of the applied signal. It
certain rate, means for modulating said cathode
will be understood that the capacity elements of
ray by said reflected pulses whereby an image
the mosaic 1| acquire different charges in this
of defiecting coils 11 connected to the sawtooth
generator 21. The cathode ray in the right hand
section of tube 65 is deflected along this same
manner because the electrode 12 collects more or
less secondary electrons from them depending“
thereof is stored on said screen, means for scan
ning said screen at a frequency lower than said
certain rate, and means for simultaneously tak
ing signals off said screen Vat said lower frequency
to produce pulses at said lower rate, a cathodev ray
and may be taken oil` at any time by causing the
indicator tube having a beam control element,
electron beam produced in the right hand end
means for applying said pulses occurring at the
of the tube to scan the other side of the mosaic 60
lower rate to saidcontrol element, and means for
1|. As this other side of the mosaic 1| is scanned,
deflecting the cathode ray of said indicator tube
secondary electrons are released from the mosaic
at said lower frequency.
~
and collected by the electrode 13 whereby the
3. A system for reducing the frequency band
_pulse signal appears across the resistor 16. It
required to transmit the information contained
will be understood that this output signal is pro
in a wave consisting of electrical pulses recurring
duced because the number of secondary electrons
upon its potential.
.
_
Thus a pulse signal is stored on the mosaic 1i
. going from a picture or capacity element of the
, periodically at a certain rate each of which occurs
mosaic 1I to the-.collectorv electrode 13 depends
upon the potential difference between them, this
depending upon the charge of the individual pic
reference pulse, said system comprising a cathode
at a certain time after the occurrence of a time
ray tube having a fluorescent screen which has a
certain persistence of fluorescence, means for
modulating the cathode ray of said tube by said
first pulses, means for deflecting said cathode ray
parent that pulses are supplied to the telephone
at said certain rate whereby there is stored on
line which recur 30 times per second and which
occur at a time following the instant of pulse 75 said screen an image of said iirst pulses with said
ture or capacity element.
_
From the foregoing description it will be ap
image spaced from a time reference point by an.
- amount determined by said deiiection rate, opti
cal means i‘or scanning the image on said screen
at a lower rate than said certain rate, and means
for simultaneously taking signals ofi.' said screen
at said lower scanning rate for converting said
stored image to pulses recurring at said lower
object, means for transmitting pulses to sam ola»-4
ject from a rotating directional antenna whereby
they are reñected from said object, said pulses
recurring at a certain pulse repetition rate,
means in the region of the transmitting meansl
for receiving said reñected pulses, there being a
certain time interval between said transmission
and reception, a cathode-ray tube having a stor
rate.
4. In a system for indicating the position of
age screen and means for directing a cathode ray g
an object, means for transmitting pulses to said 10 against said screen, means for modulating said
object from a. rotating directional antenna
whereby they are reflected'irom said object, said
pulses recurring at a certain pulse repetition rate,
cathode ray oi.' said tube by said received pulses.
means for deflecting said cathode ray at said
pulse repetition rate whereby there is stored on
means in the region of the transmitting means
said screen .an image ot said received pulses with
for receiving said reflected pulses, there being a 15 said image spaced from a time reference point by
certain time interval between the instant of
an amount that is a function of said certain time
transmission of a pulse and the~ reception of said
interval, means for scanning said time reference
pulse, means for converting said reñected4 pulses
point and the image on said screen at a lower
to pulses which recur at a lower rate than said
scanning rate than said pulse repetition rate, and
certain pulse repetition rate with each pulse oi 20 means for simultaneously taking signal on said
said lower rate occurring at a time interval fol
screen at said lower scanning rate for converting
lowing a time reference instant which interval
said stored image to pulses recurring at said lower
is equal to the ratio of said certain pulse repeti
rate, a cathode ray indicator tube, means for ap- '
tion rate to said lower rate times said ñrst time
plying the pulses occurring at said lower rate to
interval, a cathode ray tube including electron 25 said tube to modulate said beam, means for radi
beam producing means, means for applying said
ally deiìecting the electron beam of said indi
lower rate pulses to said tube to modulate said
cator tube, means for rotating the plane of said
beam, means for radially deñectin‘g the electron
radial deflection in synchronism with the rotation
beam of said tube, means for rotating the plane
of said antenna, and means for producing said
of said radial deflection in synchronism with the so radial deñection at said lower scanning rate with
rotation of said antenna, and means for produc
the deiìection from center starting substantially
ing said radial deñection at said lower rate with
at the instant of scanning said time reference
the deiiection from center starting substantially
point.
at said time referenceinstant.
`
' 5. In a system for indicating the position oi’ an 35
ALDA V. BEJDBI’ORD.
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