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Патент USA US2410068

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at; 29, 1946.
B, M_ HANSON
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2,410,067
SUBMARINE SIGNALING
Filed Sept . _ 23, 1958
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FREQUENCY OF '
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HETRODYNE
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RECEIVER AMPLIFlER
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INVENTOR.
BERTRAM M. HARRISON
Patented Get. 29, 1946
ST’ES
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2,410,067
SUBMARIINE SIGNALING
Bertram M. Harrison, Newton Highlands, Mass,
assignor, by mesne assignments, to Submarine
Signal Company, Boston, Mass, a corporation
of Delaware
Application September 23, 1938, Serial No. 231,390
6 Claims. (01. 177—386)
1
2
to assist in identifying the successive echoes it is
highly desirable that each transmitted signal be
an exact duplicate of every other signal. This
means that the initial and ?nal frequencies of
all signals must be the same.
A schematic arrangement of the apparatus and
circuits whereby the invention may be carried
The present invention relates to a method and
apparatus for sound ranging, that is for the de
termination of the presence and location of ob
jects in water.
In general in practicing sound ranging a pro
lector capable of emitting a beam of compres
sional waves in water in substantially a horizontal
. out is shown in Fig. l of the drawing and in Fig.
direction is used to detect the presence of objects
2 a modi?cation of a detail of the same.
in the Water and to determine their distance from
A projector I suitable for the emission of com
the projector by the echo method, that is by de 10
pressional waves in water, preferably of super
termining the time required for the compres
sonic frequency, may be mounted outside of the
sional waves to travel to the reflecting object and
skin 3 of the ship so that its direction of trans
return to the receiver. I-Ieretofore signals of var
mission may be controlled by means of the motor
ious lengths but of constant frequency have been
4. The device I may, if desired, also be used for
used.
receiving, as shown, or a separate receiver may be
In my copending application Serial No. 174,081,
employed. The projector is energized by an ‘elec
?led November 11, 1937, however, it was pointed
tric frequency generating source 5 which provides
out that such constant frequency signals are not
a suitable alternating current. The frequency of
always desirable. The propagating medium,
the source is caused to vary through a predeter
namely the water, is bounded by de?nite top and 20 mined
frequency band by means of a variable
bottom surfaces which, being irregular, may cause
condenser E driven by the motor ‘i when the latter
re?ections if any part of the transmitted beam
is energized. The received re?ected signals may
happens to strike them. Moreover, re?ections
be made audible by a receiver ampli?er 8 and the
may also be caused by the non-homogeneous
telephones
if desired, visual indications may
character of the Water medium. >Such miscel 25 be produced9 or,
by
apparatus known in the art.
laneous re?ections, when heard in the receiver,
The operation of the system is controlled by
have the character of reverberations which may
a key l0 through a series of relays. A transfer
completely obscure the re?ection or echo from
relay H connects the projector I to the ampli?er
the object which is being observed. Consequently
8 except when the relay coil is energized, in which
these multiple re?ections or reverberations great
case the projector l is connected to the source 5.
ly reduce the possible distances over which sound
The source 5 is in turn energized by the power
ranging may be practiced. As pointed out in my
above-mentioned application, the effect of the
reverberations may be substantially reduced by
control relay H]. The relay l4 energizes the motor
1; while the relay I2 is an interlocking relay
providing a continuous frequency modulation of 35 whose contacts are in parallel with the key It
and whose operating coil is in series with the
the transmitted signal.
contact Hi. The motor ‘I drives the movable
According to the present invention the effect
plates of the condenser 6 and simultaneously
of the multiple echoes or reverberations is sub
therewith the lever it which at the end of its
stantially entirely eliminated by providing that
the frequency modulation of the transmitted sig 40 stroke opens contacts I3. Upon the opening of
these contacts all the relays become deenergized.
nal extend Over a de?nite frequency band and
It will be noted, therefore, that the length of each
further that the receiving system be sharply tuned
transmitted signal is the same regardless of the
and have a band pass which is somewhat smaller
length of time the key Ill may be depressed.
than the frequency band of the transmitted sig
Thus, the closing of the key It] causes the si
nal. Moreover, I have found that the frequency 45
multaneous closing of all the relays whereupon
band of the receiving system should lie wholly
the projector l emits a signal continuously vary
within the frequency band of the transmitted
ing in frequency and having a definite time length
signal so that the latter will begin outside of the
range of the receiving system, sweep through the , as ‘determined by the opening of contacts l3. vAs
operating band of the receiver and terminate out 50 soon as the transmission of the signal is com
pleted and the contacts l3 open, the relay ll re
‘side the band on the other side of the band from
sumes its initial position in which the projector l
which it started.
is connected to the ampli?er 8, whereupon the
It will be understood, of course, that it is imma
receiving system is in condition for the receipt
terial whether the frequency of the emitted sig
nal is made to increase or to decrease. However, 55 of echoes.
2,410,067
3
As previously discussed, the entire receiving
system, which comprises the receiving device I
and the ampli?er 8 together with any ?lters it
may contain, has a frequency pass band of rela
tively sharp cutoffs and of a width which is slight
1y narrower than the band of frequencies in the
emitted‘ signal. Moreover, the limits of the pass
band of the receiving system lie wholly within
the frequency band of the transmitted signal.
By means of the present invention substantiah
ly no sound is heard in the listening device 9
except that caused by the echo from a re?ecting
object lying directly within the path of the beam
of waves transmitted by the ‘projector. It will be
understood that for the purposes of the present
invention any suitable means of progressively
4
prises transmitting a beam of supersonic com
pressional waves continuously varying in frequen
cy between predetermined frequency limits, the
said limits including the sensitive frequency band
of the receiving system and observing the re?ec
tions from objects in the path of the emitted
signal.
2. In a system for sound ranging, in combina
tion, a projector adapted to project a beam of
supersonic waves, an electric frequency generat
ing source connected therewith for operating the
same and means for operating the source to cause
the projected beam of compressional waves con
tinuously to vary in frequency over a predeter
mined band'of frequencies, a receiving system
adapted to receive the re?ected compressional
waves, said receiving system being sharply tuned
varying the frequency of the transmitted signal
and adapted to pass only a band of frequencies
may be used in place of that shown in the draw
entirely comprehended within the frequency band
mg.
Where a heterodyne receiver ampli?er is used, 20 of the transmitted signal.
it is not necessary to sweep the frequency of the
3. In a system for sound ranging, means for
transmitted signal entirely through the pass band
projecting a beam of supersonic compressional
of the receiver, but it is suf?cient, and often more
convenient, to sweep the frequency of the trans
mitted signal from a point outside of the pass
band of the receiver to the frequency correspond
time length and continuously varying in frequen
cy between predetermined frequency limits and
waves in the form of a signal of a predetermined
means for receiving re?ected waves, said means
transmitted signal may progressively sweep from
being responsive only to a frequency band entire
ly contained within the frequency limits of the
25,000 cycles to 23,000 cycles during the signal
transmitted waves.
ing to zero beat or vice versa.
For instance, the
4. In a sound ranging system, in combination,
period and the receiving system may be tuned 30
a tuned projector, a tuned receiving system hav
with a band pass ranging from 24,000 cycles to
ing a band pass frequency characteristic, and
‘22,000 cycles with the heterodyning frequency set
means for supplying current to' said projector to
at 23,000 cycles. In this case zero beat will be
transmit a signal of continuously varying fre
reached when the signal frequency is 23,000 cy
quency having de?nite frequency limits lying out
cles. This eliminates reverberations as heard in
side the frequency band of the receiving system.
the listening device as completely as though the
5. In a sound ranging system, means for trans
signal frequency were swept completely through
mitting compressional waves, a receiving system
the receiver pass band.
for said waves having a band pass frequency
It has been found that a rate of change of fre_
quency of the transmitted signal of 2000 cycles 40 characteristic and including a hetero-dyne cir
cuit, and means for actuating said transmitter
per second or higher is usually satisfactory.
to transmit a signal of continuously varying fre
It should be noted that, in the present system,
quency between two frequency limits, one limit
of necessity both projector and receiver including
lying outside the frequency band of the receiving
receiving circuits are for practical reasons high
system and the other limit at the frequency cor
ly tuned and that as a result impact excitation
responding to zero beat in said heterodyne.
either in the projector or in any part of the re
6. The method of sound ranging in water with
ceiving system may cause ringing at the natural
the use of a high frequency beam projector and
frequency of the system and add to the difficulties
a high frequency receiving system which com
of faithful reproduction or receipt of the echo or
reflected signal. By means of the present inven 50 prises transmitting a beam of supersonic com
pressional waves continuously varying in frequen
tion this difficulty is avoided and the signal in the
cy between predetermined frequency limits, the
receiver will gradually build up and not cause
said
limits overlapping at least at one end the
shock excitation of it.
sensitive frequncey band of the receiving system
Having now described my invention, I claim:
1. The method of sound ranging in water with 55 and observing the re?ections from objects in the
path of the emitted signal.
the use of a high frequency beam projector and
EERTRAlVl M. HARRISON.
a high frequency receiving system which com
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