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Патент USA US2407273

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Sept. 10, 1946,
R_ w, HART
Filed March 5, ‘1955
2 Sheets-Sheet 1
' 6
" 30
Sept. 10, 1946.
R. w. HART
Filed March 5, 1935
2 Sheetsy-sheet 2
Fatented Sept. 10, 1946
Robert W. Hart, Lynn, Mass, assignor, by mesne
assignments, to Submarine Signal Company,
Boston, Mass, a corporation of Delaware
Application March 5, 1935, Serial No. 9,459
9 Claims. (Cl. 250-1)
be measured and the measurement of the time
interval between the transmission of such an im
pulse and the return of its re?ected echo or Wave.
It is usually assumed that the transmission of
electromagnetic waves for most measuring pur
and also to the measurement of distance of an
poses is instantaneous and under this assumption
aircraft from some point of observation.
distance has been measured by the use of syn
The invention may also apply to the measure
chrom‘zed sound and radio signals.
ment of distances at sea between a vessel equipped
However, it is a known fact that electromag
with the invention and another distant vessel
within the range of the apparatus.
10 netic waves travel with the velocity of light, and
it will, therefore, be understood that by measure
Not only may the present invention be applied
ment of the time interval between the transmis
to distance measurement but it may also be ap
sion and the reception of the corresponding elec
plied to direction ?nding and in such cases fur
tromagnetic wave impulses, the remoteness of a
nish accurate knowledge of the position of a dis
tant object. While it is true that for measure 15 distant object may be measured. Assuming the
velocity of electromagnetic waves 300,000,000
ment of distances of vessels the necessity of ?nd
meters per second, it will be appreciated that for
ing practically instantaneous observations is not
The present invention relates to distance
measurement and in particular with the use of
electromagnetic waves. It is particularly appli
cable to measurement of heights from an aircraft
the measurement of a distance of 30 meters, the
so essential, nevertheless in the measurement of
time interval of 140,000,000 of a second must be
heights of aircrafts and the location of aircrafts
from the ground observation station, the factor of 20 measured, and that for a measurement of a dis
tance of, say, 50 feet, the time interval is even
velocities and time used in the measuring methods
shorter. In the present invention these time in
becomes very important. With measurements by
tervals are directly and accurately measured and
the use of sound waves under such conditions,
with such accuracy that the apparatus may be
particularly with the increase of velocities of air
crafts, the velocities of the aircraft as compared 25 generally commercially used.
The present invention will be more fully de
with the velocities of sound, if sound is used as
scribed in connection with the drawings in which
a measuring means, may be as high as 20%. In
Fig. 1 shows schematically the system; Fig. 2
other words, an aircraft determining its height at,
shows a detail of the indicator; Fig. 3 shows a
say, a distance of 1000 feet, may have moved a
position of 200 feet from the point at which the 30 further detail of the indicator; Fig. 4 shows a
modi?cation of the detail of Fig. 3; Fig. 5 shows a
measurement is begun. If the sound wave, there
sectional view of a modi?ed detail of that in
fore, was sent out in a beam, it would under many
dicated in Fig. 3; and Fig. 6 shows a further modi
circumstances not be returned to a position to be
?cation in a view similar to that shown in Fig. 3.
received by the aircraft in its flight and the
In Fig. l the electromagnetic impulses may be
measurement of distance by sonic methods under
sent out by a directive transmitter which includes
these conditions might be seriously impaired. It
a very high frequency oscillator l which is prefer
is easily understood, therefore, how directive com
ably shorter than 1 meter. This oscillator is de
pressional wave signaling for this purpose may
signed to produce continuous waves and has been
readily f all.
used at a Wave length of 60 cms. The transmitter
It is also true, particularly at high speeds, that
may be provided with an antenna 2 of the form
a good deal of extraneous sound is present and
known as a doublet and may be made directional
this makes it necessary either to have a compres
by making the antenna 2 the focus of a paraboloid
sional wave producer of high power or to go to
3. Other directive systems may be used such as
such frequencies where the attenuation in the air
is very great. Due to these factors and due also 45 an antenna array in which a re?ector, such as
paraboloid 3, is omitted and the directive e?ect is
to the fact that the apparatus itself is quite heavy
obtained by the group of antenna alone.
and quite bulky, it may safely be said that no
While the oscillator I is of the continuous type,
practical height-measuring device using compres
it is not, however, allowed to‘ oscillate except
sional-wave means has at the present time been
momentarily when the grids 4 and 5 are made
su?iciently positive by means of the pulse ampli
rfhe present invention, as has been stated, em
?er 6 which Will be explained later. At these in
ploys electromagnetic waves and applies as its
stances the grid potential upon the grids 4 and 5
principle of operation the transmission of a short
become sufficiently positive so that the oscillator
train of electromagnetic waves at very high fre
quencies towards the object Whose distance is to 55 may continue to operate at its resonant frequency.
The impulse transmitted by the directive system
provided with a ?uorescent screen in the usual
fashion while the outside of the face of the tube
may be provided with a scale as indicated in
may travel in a ray or beam to a distant object
or surface I or the radiation may be in all direc
tions if no directive system is used. The wave
re?ected from the surface or object 7 is picked
up by the receiving antenna 8 which may simi
Fig. 2. The pair of plates l4, l5, l6 and I7,
respectively, are controlled and operated by a
sweep circuit oscillator 25 which is preferably
chosen to impress a sinusoidal voltage on the pair
of plates to create a rotating beam. However, if
larly, as the antenna 2, be located at the focus of
a paraboloid 9 of the pick-up system.
The impulse received or picked up by the an
the shape of the tube were changed or even if
tenna 8 is impressed upon the grids l0 and II 10 the shape of the tube were not changed, a sweep
of the radio receiver which preferably is of the
circuit might be used in which a different pat
same type as the transmitter just previously de
tern of the beam is obtained. This obviously
would depend upon the relative positions of the
scribed. This receiver should preferably be
tuned to the frequency that the transmitter is
scale and the electrode 2| as will be learned from
and in the present case has been usually adjusted
the description given below. The sweep circuit
oscillator 25 is used preferably at radio frequen
to a Wave length of less than a meter, 60 cms.
having been found workable in the present case.
cies although frequencies lower than radio fre
quencies may be employed, the adjustment of the
Both transmitters and receivers may be read
frequency, as will be shown, limiting and being
ily tuned and, as indicated in Fig. 1, the tuning
of the receiver is accomplished by the adjust
associated with the distance to be measured.
ment of the slipping contacts 70 and ‘H at oppo
The best range of frequencies for the sweep cir
site ends of the bar 12. By this means plate
cuit in the present invention is that of the order
of a frequency of 100 kilocycles and depends, as
conductors ‘l3 and 74 may be adjusted in length
to provide proper plate tuning for the circuits.
The transmitter may be similarly adjusted by
adjusting the 13+ taps along the plate conductors
l5 and 1E. The adjustment of the length of the
conductors l5 and ‘It and also conductors l3 and
has been stated, upon the upper as well as the
lower limit of distances to be measured. The
sweep circuit oscillator in this respect may be ad
justed so that the desired frequency within the
range of operation of the apparatus may be 0b
'14 may be accomplished by means of hollow tele
7 tained.
In order to reliably control the pattern of the
scopic tubes, or, if desired, an actual wiping con 30
tact may be made.
beam, the potential of the plates I 4, l5, l6 and
The impulse from the radio pickup unit is im
H’ and the anode I8 are kept at a ground poten
pressed upon the ampli?er l2 before being im
'tial and the cathode 20 is placed at the neces
pressed upon the indicator or measuring system. . sary potential below ground to produce the dis
The indicator or measuring system includes a
charge of the electrons from the anode so that
cathode ray tube i3 which is preferably of the
a proper beam may be produced.
type that is quick acting and will produce a beam
In Fig. 2 the front end of the tube I3 is shown.
which will follow at very high frequencies. Such
The tube may be provided with an opaque an
cathode ray tubes are usually of the high vac
nular portion 26 and a center opaque portion
uum type having very little gas to retard the 40 21, leaving a ring 28 through which the electron
progress of the electron stream even at very high
beam may show on the fluorescent screen. The
frequencies. Such tubes are operable quite read
scale 29 may be and preferably is placed upon the
ily at radio frequencies of 300 megacycles per
outside of the ring 28 on the opaque surface 26.
second which is well within the range of opera
In the modi?cation shown in Fig. 4 the struc
tion of the present system.
ture differs from that shown in Figs. 2 and 3
The cathode ray tube 13 is quite similar to
only in the fact that the strip is ?xed in another
the usual type of tube, it being provided with
position. The tube may be provided with a plate
two pair of static de?ecting plates I4, l5, l6 and
33 which is spaced away from the front end of
II and an anode gun or tube l8 which has a
the tube so that there is no possibility of sec
cylindrical opening through which the beam
ondary conduction from the ?uorescent surface
passes, a control grid I9, and a filament or cath
363 on the inside of the end of the tube. There is
similarly provided on the outside of the tube an
ode 26. Besides these elements the tube may
opaque center disc 35 and a ring 36 whereby a
have a metallic deposit over the ?are inside sur
circular opening 3?’ will be provided. If neces
face of the bulb for establishing electrostatic ?eld
sary, the plate 33 may also be provided with a
conditions necessary for focusing the electron
slightly negative potential to repel any secondary
beam although if the beam may be properly
emission which may occur from the ?uorescent
focused without such a special anode, this may
screen 34. It should be noted that the strip is
be dispensed with.
indicated in Fig. 2 as rectangular in shape. Any
In addition to the above elements, the tube
is provided with a metallic plate or strip 2| which 60 shape of strip may be employed, but it is prefer
able to use a strip or plate such that the angle
is preferably seated on the inside of the ?at end
subtended from the center of the indicator will
22 of the tube. The plate or strip 2| is conduc
be di?erent for a different radius of the rotating
tive and may be rectangular as indicated in the
beam. In this way by varying the size of the cir
?gure or may form a sector, depending to some
extent upon the exact use to which the system 65 cle of the rotating beam, the length of signal will
be controlled and varied, since if the angles sub
is applied.
tended by the beam crossing the plate are dif
The electrode or strip 2|, as indicated, is con
ferent, the time during which the signal will be
nected by the wire 23 to the pulse ampli?er 6,
the pulse ampli?er being connected also by the
applied will also be different, and, therefore,
wire 24 to the ground 80. In this way when the 70 either a longer or a shorter signal may be pro
vided by’ varying the position of the rotating
electron beam impinges upon the strip 2| a cur
rent will be set up in the pulse ampli?er 6 which
A further modi?cation is shown in Fig. 5. In
will react to control the operation of the trans
this ?gure the cathode ray tube 40 is provided
with two plates 4| and 42 which may be in disc
' The inside of the face 22 of the tube may be
form, the plate 132 having an opening therein
as indicated at 43. The plates may be connected
together through a resistor 44 external of the
tube, the plate Ill being grounded at 45 and the
connection at the plate £3 going to the grid 46 of
cycles emitted by the transmitting oscillator l.
The waves radiated from the transmitting system
and picked up by the receiving antenna 8 will be
impressed upon the radio receiver 30 and then
upon the ampli?er 12 which may be tuned in the
same manner as the pulse ampli?er 6. The out
a control tube whose ?lament 4'! is connected to
put of the ampli?er l2 controls the control grid
the ground 45. When the electron beam 48, as
I9. The control grid l9 preferably has an initial
indicated by the arrow, passes through the open
potential which may be in the same direction as
ing 43 in the plate I32, the current which up to this
time has flown through the plate 42 and the con 10 the received pulse or it may be in the opposite
direction, depending upon the particular type of
necting lead 43, now ?ows through the plate 4!
indication that is desired. If the received im
and the connecting lead 49. The potential there
pulse acts in the same direction as the potential
by at the point 50 suddenly drops a value de
32 upon the control grid IS, the tendency of the
pendent upon the voltage across the resistor 44.
This may be used to control or energize the grid 15 received impulse will be to decrease temporarily
the radius of rotation of the electron beam since
46. The grid 45 in the tube 80 may control the
it will produce an increased velocity of the beam
flow of plate current in the circuit by any well
and therefore tend to keep the beam in the cen
known means as, for instance, through the trans
former coupling 81, the secondary of which is
connected to the cathode 20 and the grid [9.
In the modi?cation shown in Fig. 6 the cathode
ray tube 40 is provided with a plate 6| positioned
ter of the scale.
On the other hand, if the potential 32 is in the
other direction, the velocity of the beam will de
crease and the radius of rotation of the beam will
thereby increase. As has been stated above, the
somewhat close to the ?uorescent screen 62 on
beam rotates continuously at the speed of the
the inside end of the tube. An electrode 03 is
sweep circuit oscillator, sending out an impulse
provided which may be a plate or a strip some
by control of the pulse ampli?er 0 when it crosses
what as indicated in Fig. 4. The plate 61 may be
the strip 2|. The beam may at all times be Within
?at or is preferably provided with a turned-back
the center circular portion 21 until such instant
?ange. The electrode Si is connected to the grid
when the received impulse acts upon the grid 19
54 and also to the resistor 65 which is in circuit
in such a way as to momentarily cause the beam
with the battery 00 and ground Bl.
to appear in the ring 28. This will occur at the
A variable tap 68 may be provided for the oath
time of the receipt of the re?ected impulse and if
ode 59 of the tube. In the operation of the tube
the scale is properly calibrated in distance will
the electron beam is rotated and is not inter
indicate momentarily the distance of the source
rupted until it is intercepted by the electrode 03.
At other times than when the beam is inter 35 from which the re?ection is returned.
It is obvious, of course, that a single impulse
rupted a secondary emission occurs from the
would not be visible on account of the tremendous
?uorescent screen 52 which causes an electron
velocities involved and, in fact, the beam itself
?ow between the screen 62 and the plate M.
would not become visible unless the image re
This ?ow is interrupted at the instant that the
mains suf?ciently long or was repeated su?iciently
beam hits the electrode 63 and at such times the
often to produce an impression. At the present
current through the resistor 65 reduces to zero.
instant, however, since the sweep circuit is oper
ated at approximately 150,000 times per second,
that of the plus side of the battery 06. This
there will be 150,000 impulses sent out from the
short drop may be used to control the current in
the transmitting circuit. The grid 04 may con 45 transmitter each second and likewise 150,000 im
pressions or measurements of the distance every
trol the grid of the cathode ray tube in a man
ner similar to that described in connection with
Even if it is assumed that the position of the
Fig. 5 through the transformer coupling element
object relative to the measuring station is moving
The potential, therefore, of the grid 04 drops to
In the operation of the general system as set 50 with the greatest velocity that is possible, since
these velocities do not compare with the velocities
forth in Fig. 1 the sweep circuit rotates the elec
involved in the present measurement and with
tron beam continuously at a velocity dependent
the number of measurements per second, it is
upon the frequency of oscillation. With an os
obvious that the relative position of the objects
cillating frequency of, for instance, 150 kilocycles
and the measuring station may be considered as
per second, the beam will make one revolution
stationary during any measuring interval. It
of the scale in 1/150,000 of a second. If the beam
should be noted that within the shortest period
crosses strip 25 at such a radius as to subtend an
that the eye can register which we may assume
angle of, say, two degrees, the pulse ampli?er will
as perhaps 1/100 of a second, there will be 1500
be energized from the beam for 1/180 of 1/150,0'O0 of
a second or for a time interval of 1/27,000,0oo of a 60 measurements indicated in the same spot on the
measuring scale. From this it readily follows
second or for approximately 4><1O—8 seconds.
that a continuous indication of distance will be
The pulse ampli?er is adapted to control and
handle an impulse of this character and for this
The scale 29 must be calibrated so that the
reason has a broad timing range within a wave
values there represented are equivalent to the
length of from 10 to 25 meters. This, in fact,
time of travel of the impulse from the transmit
may be adjustable to correspond to the time in
ter to the re?ecting surface and back to the re
terval created by the duration of the impulse it
ceiver again. Since the velocity of the beam is
receives. The impulse received by the pulse am
dependent upon the sweep circuit oscillator 25, it
pli?er 6 will be impressed upon the grids 4 and
5 of the transmitter and allow it to oscillate for 70 follows that for any one scale a de?nite velocity
of the beam is necessary or else a correction factor
the time interval that the impulse exists.
must be applied.
If the wave length of the transmitter is 60
If the velocity of the beam is maintained at
cms., the frequency will be 500,000 kilocycles per
150 kilocycles per second, then the full scale read
second, and for a time interval of 4><10-8 sec
onds, it will be evident that there will be 20 75 ing would correspond to 1000 meters, since in
1/150,000 of a second, the impulse would travel
trolling the operation of the transmitting circuit
2000 meters. If a second velocity of the sweep
circuit is used, a second scale can be provided or
in its place a conversion table to obtain the cor
through the rotation of the electron beam, a re
rect distance reading.
It will be noted that both transmitting and re
ceiving units may be directional, in which case
the direction of orientation of either the trans
ceiving circuit and means provided within said
tube for causing a de?ection of the beam upon
the receipt of an electromagnetic impulse,
5. In a system for measuring distance by the
use of electromagnetic waves, an indicator in
cluding a cathode ray tube having a rotating
electron beam, means normally making the path
3|, will indicate the direction of the re?ecting 10 of said beam visible and means operated at the
mitter or the receiver, as indicated by the arrow
If the echo is received and the trans
moment of reception of a re?ected wave for pro
mitter is directive, the receipt of the echo will
ducing a dark spot in the visible path of said
indicate that the transmitter is pointing in the
right direction, and, similarly, if the transmitter
6. In a system for measuring distance by the
is non-directive but the receiver directive, the 15 use of electromagnetic waves, a cathode ray tube
direction that the receiver is pointing when an
having a cathode, an anode and control-plate
echo is returned will indicate the direction of a
electrodes, an electrode positioned near the face
source. With both elements of direction and
distance known, a distant craft, either aircraft
of the tube, means providing a sweep circuit for
rotating the electron beam at a de?nitely chosen
or a vessel, may be plotted and its course deter_ 20 radio frequency, a radio-transmitting device,
Having now described my invention, I claim:
means controlling the operation of said transmit
ting device, said means being connected to said
1. Means for measuring distance by means of
electrode near the face of the tube, a receiving
electromagnetic waves which comprises means for
transmitting high frequency electromagnetic
circuit and means provided within said tube for
25 causing a variation in the beam upon receipt of
trolling the emission of said electromagnetic
an electromagnetic impulse.
'7. In a system for measuring distance by the
waves at de?nite time intervals including an elec
use of electromagnetic waves, a cathode ray tube
waves of approximately one meter, means for con
tron beam, means for receiving said impulses after
having a cathode, an anode and control-plate
re?ection from the surface whose distance is to 30 electrodes, an electrode positioned near the face
be measured, means for causing the received im
of the tube, means providing a sweep circuit for
pulse momentarily to de?ect the course of said
rotating the electron beam at a de?nitely chosen
electron beam and means cooperating with the
frequency, means provided at the end of the tube
momentarily de?ected beam for producing an
for producing a visible illuminated circle by the
indication of the distance from said surface.
35 action of the beam thereon, a transmitting cir
2. A method of measuring distance by the aid
cuit and means controlled by the electrode near
of electromagnetic waves including a cathode ray
the face of the tube for operating the transmit
tube provided with a keying plate which comprises
ting circuit at the moment the beam crosses it, a
providing a rotating cathode ray beam and send
receiving circuit and means connecting said re
ing out a short radio impulse of very high fre 40 ceiving circuit to said tube for varying the il
quency only when the beam of the cathode ray
lumination of said circle by controlling the in
tube crosses the plate, receiving the re?ected
tensity of said beam upon the face of the tube.
impulse on the receiving circuit and affecting
8. A method of measuring distance which com
thereby upon receipt of the electromagnetic im
prises generating a rotating beam of electrons
pulse the movement of the electron beam whereby
having a high frequency of rotation, generating
an indication is produced,
a train of high frequency electromagnetic waves,
3. A method of measuring distance by the aid
controlling the emission of said train by a con
of electromagnetic waves with the use of a cath
ductive path comprising said beam of electrons,
ode ray tube having an electron beam, means for
receiving the train of electromagnetic Waves
rotating said beam and a plate positioned to in 50 after re?ection from the surface of an object the
tercept the electron beam in its movement which
distance of which is to be measured, deriving a
comprises transmitting an electromagnetic wave
controlling impulse of energy from said received
of a frequency approximately one meter only
train of waves in a time interval proportional
when the beam crosses the keying plate, allowing
to the distance traversed by the re?ected wave
the rotation of the beam to serve as a measure of
the time interval between the transmission of
the impulse and the reception of the re?ected
impulse, impressing the energy of the received
impulse to de?ect the beam upon the reception
of the re?ected impulse whereby the space be
tween the'plate and the de?ection of the beam
serve as a measure of the distance.
train, and de?ecting the rotating beam of elec
trons by said controlling impulse.
9. An apparatus for measuring distance com
prising means for generating a rotating non
planar beam of electrons, means for transmitting
a train of electromagnetic waves, means opera
tively associating said beam of electrons in its
rotation with said transmitting means for con—
4. In a system for measuring distance by the
trolling the instant of emission of said train,
use of electromagnetic waves, a cathode ray tube
means for receiving the aforesaid train of Waves
after re?ection from the surface of an object the
distance of which is to be measured, and means
responsive to said receiving means for causing a
having cathode, anode and control plate elec
trodes, an electrode positioned near the face of
the tube, means providing a sweep circuit for ro
tating the electron beam at a de?nitely chosen
frequency, a radiating circuit of a frequency ap
proximately one meter, means associated with
the electrode near the face of the tube for con
visual de?ection of the rotating beam of elec
trons corresponding to the moment of the re
ception of the train of electromagnetic Waves.
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