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Патент USA US2405591

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_ Aug. 13', 1946.
Filed D69. 27, _1943
5 Sheets-Sheet l
“1,, / I
Aug. 13, 1946.
w, P. MAsoN
Filed Dec. 27, 1943
FIG: 2
FIG. 3
5 Sheets—Sheet 2
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Filed Dec. 2'7, 1943
- 5 Sheets-Sheet 3
FIG; a
li i i i?li il l i itl i i
Aug. 13, 1946.
Filed Dec. 27, 1943
5 Sheets-Sheet 4
FIG. 6
FIG. 7
Aug. 13, 39%65
Filed Dec. 27, 1945
5 Sheets-Sheet 5
FIG. 9
“R65 7'
Patented Aug. 13, 1946
Warren P. Mason, West Orange, N. .I., assignor to
Bell Telephone Laboratories, Incorporated, New
York, N. Y., a corporation of New York
Application December 27, ‘1943, Serial No. 515,731
8 Claims. (CI. 35-25)
This invention relates to training apparatus and
particularly to means for simulating conditions
obtaining in one medium in another medium
whereby operations may be carried out within
small and practical con?nes representing opera
tions ordinarily involving great distances and
reproducible only at great expense and with
great difliculty. More speci?cally the invention
tion behind the other when such beam passes
through a horizontal plane and adjusting the
angular pointing of the transducer until the size
of the two reflections are equal, the azimuth angle
can be accurately measured.
In a similar man
ner the colatitude angle may be determined.
Where an acoustic lens is used the prism may
be built into the lens by putting the center of
curvature o? the center line.
relates to means for energizing a radio detection
A split lobe modi?cation of the radio location
and ranging device from an apparatus housed 10
and ranging device can be simulated by using a
Within reasonable compass wherein conditions
crystal with two sets of platings in the form of
which such a device is intended to detect may
semicircular areas. By thus dividing the plating
be closely simulated.
in half and sending the wave through the lens,
The object of the invention is to provide a
medium whereby small scale objects within a .15 each half will have a slightly different direc
tional pattern. By comparing the output re
limited compass may be exposed to radio detec
ceived from the two different halves of the crystal
tion and ranging apparatus and cause a response
and turning the unit until the received response
therein fully equivalent to the response expected
is the same on each half, the direction of the re
in regular service for the purpose of training op
flection can be accurately located.
erators of such devices.
A feature of the invention is a means for op
In accordance with the present invention the
erating a radio direction and ranging device by
usual antenna of a radio detection and ranging
transmitting into and receiving from a medium in
system is replaced by an electromechanical trans
which the linear factors are greatly reduced.
ducer for transmitting and receiving compres
Another feature is an electromechanical trans
sional waves in a liquid medium such as water
ducer for transmitting and receiving compres
or Water mixed with some other liquid whereby
sional waves in a dense medium substituted for
the scale is shrunk by a factor of two hundred
the usual radio antenna in a radio direction and
thousand, thus making it possible to simulate the
ranging device.
distance of 50 miles in 15 inches. Sound in water
Another feature is a means for producing a
is substituted for radio waves.
rotating beam comprising a rotating acoustic
Further, in accordance with this invention and
prism placed in the beam of an electromechani
in order to get a directional pattern with a rea
cal transducer.
sonable size crystal, a transducer provided with
Still another feature is a means for producing
an acoustic lens is employed. Whereas it is de
a beam pattern comparable to that of a radio
sirable in these radio detection and ranging sys- Y
terns to project as narrow a beam as possible
for some uses, yet a reasonably broad beam ex
antenna comprising a highly directional electro
mechanical transducer and an acoustic lens in
the path of the beam.
tending to ten degrees each side of the center
Another feature is an electromechanical trans
line is used for searching and since the trainee
will ?rst be assigned to operate this type of de 40 ducer and in the beam path therefrom an acoustic
lens having its center of curvature oiT-center
vice the transducer used herein must simulate
as nearly as possible that type of device. Hence,
whereby rotation of said lens will produce a
since the piezoelectric crystal used in the trans
rotating beam.
ducer is very highly directional at the high fre
Another feature is an electromechanical trans
quencies employed the beam must be spread by
ducer comprising a crystal having split electrodes
an acoustic lens.
Other characteristics of the radio direction and
ranging devices may be simulated. A rotating
beam device may be provided by placing an acous
tic prism in the path of the beam and providing
means for rotating such prism about the center
line of the beam from the transducer so that in
a complete rotation the refracted center line will
move about the surface of a cone.
Then by ar
ranging to send out two pulses, one a half revolu
and an acoustic lens in the beam path there
from whereby a split lobe beam pattern is found.
Other features will appear hereinafter.
The drawings consist of ?ve sheets having nine
?gures, as follows:
Fig. 1 is a perspective view showing an operator
manipulating a miniature object in a tank to
simulate the movement of an aircraft and three
trainees engaged in making adjustments for
azimuth range and elevation on a device equipped
ing hand-wheels 5 and 1 by means of which he
with standard radar circuits;
may move an object 8 suspended on a ?lament 9.
By the use of these hand-wheels as well as a third
Fig. 2 is a schematic diagram coupled with a
cross-sectional view of a tank in which an ultra
here numbered It, the object may be moved to
any point Within the con?nes of the tank. The
hand-wheels may be geared so that the move
ment of the object 8 will simulate in time and
space relations the movement of an aircraft.
In Fig. 2 the arrangement of the training de
sonic transducer and an object to be measured
may be immersed to simulate the operation of a
standard radar device;
Fig. 3 is an enlarged cross-sectional and dia
grammatic view showing the construction of a
suitable ultrasonic transducer and an acoustic 10 vice is shown schematically. The tank 5, shown
lens for spreading the beam transmitted there
in cross-section, consists of a steel tank lined with
some sound absorbing material and ?lled with
Fig. 4 is a view similar to that of Fig. 3, show
water or a mixture of water and some other liquid.
ing another form of ultrasonic acoustic lenssimi
Immersed in the liquid is an electromechanical
lar to the pin hole “lens” sometimes used; in - transducer 52 which may be mechanically ro
photographic work;
tated about a vertical axisthrough the ?exible
Fig. 5 is a similar view showing a transducer
shaft It by the hand-‘wheel M. In a similar man
capable of transmitting and receiving two beams
ner an adjustment about a horizontal axis may
and arranged with an acoustic lens so that the
be made through the ?exible shaft it by the
beams diverge whereby a lobe comparison method 20 hand-wheel I6.
of measurement may be. used;.
.An: object, here shownas. a miniature. plane I1,
Fig. 6 is a similar view showing; the use of an
acoustic prism arranged to rotate on an axis
is suspended'on a ?lament 5.8. and, given three
dimensionakmovement.through the use of'hand
wheels 29, Hand?! , this showingbeing- byway of
example to; indicate one simple way in which it
can be done.
which coincides with the axis of‘ the beam trans
mitted-by the transducer whereby a. comparison
method may. be used to promote accuracy;
Fig. '7. is a similar view in, which the lens- and
the prism shown in Fig. 6 are in di?erent iorm
and are differently placed. with respect to each
Fig. 8 is a similar view of. a'device. equivalent to
the, arrangements of Figs. 6. and: 7; and
Fig. 9 is.arepresentationof the screen ofian
oscilloscope showing the type of indication. re
The essential elements of the radar system
are'shown in; the circuit diagram above. An os
cillator-ziprovides power to operate .a. pulse gen
30 erator 23 which. supplies pulses through an am.
ceived in radar operation and usedin the instruc- .
tion of' trainees.
Fig; 1 shows the general arrangement. of a
plifler. 2:5; to; a. transmitter 25; 7 Through the
transmitting-receiving circuit. 26 the. pulses of
proper frequency current are; connectedto the
channel 2i which ordinarily leads to an antenna
but’ in the present case leads instead to the
transducer l2. The. transducer; i2 transmits ul
trasonic. compressional waves which travel toward
trainingr'dev-ice by which technical; operators. may
the object. It“, or the irregular re?ecting surface 23
be trained to quickly and'accurately operate the
representing the terrain, and receives the echoes
controls of a radindetection; and ranging; device 40 therefrom, which are then‘ passed through the
by which an. aircraft. maybe accurately located
receiver, 29' and ampli?er. 353‘ to operate the oscil
in space. In. accordance with the present inven
loscope 35!. By'the sweep circuit: 32 and the ad
tion, an ultrasonic electro-mechanical transducer ’ justable range: circuit 33 interposedbetween the
is substituted fonthezusual antennaof. sucha de
pu-ise generator 23: ‘and’ the oscilloscope 3%, the
vice and; this,» transmits andreceives under the 45 indication thereon may he; made to assume the
surface- of any appropriate liquid such as water
form indicated inFig. 4. Through adjustment of
so that; a distance of‘ approximately ?fty miles
the range; circuit: 3:3 by the. hand-wheel 34, the
may be measured in, ?fteen, inches of, the; liquid.
targetecho may’ be made to occur. at the step in
The remainder of the circuit is standardithough
the general level of. the oscilloscope trace and
it may be housed; in‘ more convenient. form: for 50 through continuous: adjustment this echo may be
training purposes.
kept at thisv point. as the object‘ I l is moved.
Three trainees, are seated before a panel and
each has a hand-wheel to rotate to make ad
justments for azimuth range andelevation as in
The; radar system itself ‘uses, a transmitting an
end trainees is to make an adjustment which will
timeter in diameterv andv to then use either a cir
tennahaving'a directional pattern such that the
firstminimumv occurs» at about 10 degrees from
dicated by the designationabove the hand-wheel. 55 the normal. In order to get this directivity, the
Each is also-provided with a dial,‘ to indicate the
antenna itself: is about 6 wavelengths across. To
value to which he has adjusted his part: ofv the
get the sametdegree of directivity with a crystal
apparatus. Mounted above and in View of each
vibrating at 10 megacycles would require a crys
of the. traineesis an oscilloscope Iv by which: each
tal radiating surface about .09 centimeter in di
may judge the resultof hiseffort; In general, the 60 ameter, which is rather'small and impractical to
oscilloscopev is arranged to show a horizontal
couple to. A more practical device may be made
traceshowing on two levels. The effort of the two
with a crystal‘ with a radiating area of one cen
produce the greatest amplitude in the. target
cular. lens made of plastic as indicated in Fig. 3
echo while. the effort of‘ the center trainee. is‘ to 65 or a thin sheet of pc. rubber: with a .09 centimeter
make an adjustment which will hold the target
hole cut in it as indicated in Fig. 4. A. suitable
echo asnearly as possible atthe point where the
plastic is knownhaving a velocity of 202x105
horizontal trace changes itslevel.
centimeters per second‘ as compared to a velocity
The hand-wheels operated by the trainees mak
of. 1.5><1i)5 centimeters per. second for water so
ing adjustments for azimuth and elevation will 70 that by‘ using: alens thicker in the. middle than on
operate through ?exible shafts 2» and- 3 to move
the electromechanical transducer which is‘ im
mersed in the tankv 5. The electrical connections
to' the. transducers are made over conductors 4.
An instructor is. shown behind theqtank 5'ope-rat
the outsid'eadiverging source is obtained. Since
the. radiation fromthe: crystal'is very directive, it
can be considered as a source at in?nity; andithe
radiation'i‘rom- the lens can be considered as com
ing- from the virtual‘ focus +- of the lens, which
can be placed at any desired value by shaping
the lens. By adjusting the position of the vir~
tual focus, the beam width can be spread at any
angular value 0 desired to simulate the radar
antenna system.
This system has the further advantage that a
much larger area is available from which to
radiate energy and the loss introduced by the
liquid can be made up by the larger amount
radiated from the source, and the large amount
of re?ection picked up by the lens and concen
trated on the crystal.
For a crystal one centi
meter in cross-section vibrating at 10 megacycles,
the diameter is 66.6 wavelengths in water, com
pared to 6.6 that it would have to be to get the
same directional pattern without the lens.
" the same limiting energy per square centimeter;
the water. The best available ?gure for attenu
ation of a plane sound wave in water is
A=0.25>< 1045]e2 nepers per centimeter.
At a frequency of 10 megacycles, this gives an
attenuation of
A=.025 nepers per centimeter=.2l7 decibel per
For a path length of 30 inches, which corre
sponds to a radar distance of 50 miles, the at
tenuation amounts to 16.5 decibels which repre
sents the added loss above that given by the
spreading out effect. This can more than be
made up by the additional power put in by the
large crystal and lens system.
However, at 20
megacycles the attenuationloss is four times this n
?gure, or 66 decibels. Hence a frequency between
this represents a gain of 20 decibels on transmit
10 and 20 megacycles will be so high as can prac
ting and a gain of 20 decibels on receiving. On
be obtained.
the other hand, the lens system limits the near
Such an electromechanical transducer unit is
ness of approach of a re?ecting system to the
placed in a tank which gives negligible reflections
radiating system. For the pc rubber with a hole
from the walls at 10 megacycles. This is easily
cut in it, the rubber acts as a very good absorber,
by lining the walls of the tank
as will be discussed more in detail hereinafter, and
with a half inch sheet of pa rubber, since meas
allows only a radiation from the right size area to
urements have shown that this has an impedance
occur. This system allows a close approach but
very close to that of water and an attenuation
does not have the gain of a lens system.
amounting to six decibels per centimeter at 1.5
A simple crystal system for a radiator is shown
megacycles. Since the attenuation increases pro
in Fig. 3. The crystal 35 may be two centimeters
in diameter and have the middle centimeter 30 portionately to the square of the frequency, this
would amount to 26'? decibels per centimeter at
plated on both sides. A small tab leads from the
10 megacycles or 30.7 nepers per centimeter.
outside plating to the edge of the crystal which
Hence, a relatively thin section would give suf
is plated all around so that it can be soldered
?cient attenuation to annul any back surface
into a thin metal shield 36. This soldered joint
re?ections. The front surface reflections can
keeps the water from coming into the inside
chamber. The crystal is .28 millimeter thick for
a half wave length crystal at 10 megacycles, and
is backed up by air on the inside and water on the
outside. A crystal system similar to this is ana
be calculated from the impedance looking into
the rubber, which for a viscous medium such as
rubber is given by
lyzed in the book “Electromechanical Transducers
and Wave Filters,” by W. P. Mason, chapter
VII, and it is there shown that a 10 per cent
where p is the density of the material, '0 the veloc
band or a one megacycle band at 10 megacycles
'ity of propagation, A the attenuation in nepers
can be efficiently radiated provided that the
per centimeter and f the frequency in cycles per
crystal reactance is annulled by a coil or trans 45 second. Since the product of density and Veloc
former 31. To get the maximum e?iciency re
ity matches that of water, the front face re?ec
quires a pulse of at least 10 cycles long or about
tion factor should be
one microsecond pulses which is in the order of
those used on radar systems. The eiiiciency of
1: .0366: 28.7 db. down
conversion for this system is rather high.
The transformer 3'5 comprises one winding
Hence, a thin layer of pa rubber is a sufficient
connected between the metallic housing 36 and
damping medium and might be incorporated in
the inside plate of the crystal and another wind
the tank as the lining H shown in Fig. 2.
ing connected through a suitable condenser 38
While the invention contemplates the use of
to the conductors 39 and 48 leading to the radar 55
any liquid as a transmission medium, practical
circuit, such as conductors 21 of Fig. 2. A plastic
considerations dictate the use of water. If it is
lens 4| is mounted on a cage which is threaded
desirable to keep its velocity relatively constant
on the housing 36 and may be locked in an ad
around 25° C. about 35 per cent by weight of
justed position by the lock nut 42. The compres
sional wave from the outside face of the crystal 60 ethylene glycol may be added. This has the
property of ?xing a peak velocity at about 25°
and the widened beam after it has passed through
C. with very slight decreasing values above and
the lens is indicated by the broken vertical lines.
below this temperature value. This amount of
A similar arrangement is shown in Fig. 4 but here
ethylene glycol will also prevent the water from
the lens 4| is replaced by a thin sheet of pC rub
ber 43 with a hole of the proper dimensions cut 65 freezing down to a low temperature.
A split lobe modi?cation of the radar can easily
through it along the aXis of the device.
be simulated by using a crystal with two sets of
Ordinarily cavitation in the water limits the
platings as shown in Fig. 5. By dividing the
power output from a crystal unit to about one
inside plating in half and sending the waves
third of a watt per square centimeter. There are
indications, however, that cavitation is a process . through the lens 44, each half will have a slightly
different directional pattern, as indicated by the
that requires time to develop and that for a very
lobes shaded by the broken lines. By comparing
short pulse the energy density that can be put
the output received from the two different halves
in the water may be considerably higher than
of the crystal, and tuning the unit until the re
this ?gure. The upper frequency limit of a unit
of this type is set by the attenuation existing in - ceived response is the same on each half the
,7 ,,
direction of the; re?ection can be accurately lojz-f"
cated as initheeradar system'itself.
4. In a; device for. training operators of a radio
detection and rang-ing'system a liquid compres
In Fig. 5 the worm and gear t5 and £38 rep,
resent the means simil'arto that operated by the
sional wave transmission‘ medium, movable re
flecting surfaces in said'medium and an electro
?exible shaft‘ i510f1 Fig. Z'fo'r making elevational
mechanical transducer responsivetoenergy con
adjustments. In this case a geared/‘ll may. beat
ventionally transrr-iittedv to the antenna of ‘ such
tachedjto the: casing 0,8 so that. by av pinion 59
a system for; translating to and from compres
operated by a flexible shaft 50 the unit may be
sional waves in said liquid medium when said
rotated on its axis for the purposes described.
transducer is immersed therein for simulating the
A'- rotating beam type of radar can be simu 10 action of the radio antenna in a conventional
lated in several ways; For the pin hole type of
radie- detection and' ranging system, said‘ trans
radiator shown in- Fig. 4, a prism 5| mounted in
ducer. comprising‘ a narrow beam projector and
a frame 5Z‘may be arranged to rotate about the
an acoustic lensplaced in the-path of the beam
longitudinal‘ axis of the device. This Will rotate
for broadening the; said beam to simulate the
the direction of'the beam and by sending out two 15 pattern of the beam from the said conventional
pulses when the' diverging beam is in. the two
positions in!’ the same horizontal plane and ad
5... ma device fortraining operators of a radio
justing the ‘angle until the size of-the two re
detection‘ and ranging system,’ a substitute for
?ectio-ns is equal, the azimuth angle can be
the conventional antenna thereof comprising an
accurately measured. By sending out pulses as 20 electromechanical transducer'immersed in a liq
the beam passes through a common vertical plane
uid compressional wave transmitting medium,
the celatitude angle is also determined. The
said transducer having an inherently narrow
shaft 53' and the cam tad-represent means to trans
beam, lobe pattern of transmission, said trans
mit pulses at proper intervals in the rotation of
ducer being provided with additional means for >
‘ 25 broadening the lobe. pattern thereof to simulate
For‘ithe lens type system, shown in Fig. 7,‘ a
the lobe pattern of said replaced antenna, said
prism 55Ibetween the crystal 56‘ and the lens 51
broadeningv means comprising a sheet of energy
will perform the same function. The prism can
absorbing material pierced by an opening of small
be built into the lensby putting the center of
dimensions. placed directly in the beam of said
curvature oi? the center line as indicated by the 30 transducer, said sheet being normal to said beam.
edge section of a, lens'58‘in Fig. 8.
6. In a device for training operators of a'radio
Small models of ‘airplanes and different types
detection and ranging system, a/substitute for, the
of're?ecting backgrounds can be simulated by
conventional antenna thereof comprising an elec
small scale models. The ?lament 9 shown in Fig.
tromechanical transducer immersed in a liquid
1 maybe [plastic having properties matching wa~ 35 compressional wave transmitting medium, said
ter sothatit will not offer any competing reflec
transducer being provided with an acoustic prism
tions. In this way the complete action of'a radar
rotating about an axis‘ coinciding with the axis
system can be simulated and a simple and com»
of the transmission-beam‘ of said transducer.
pact trainer obtained which can be put in a small
'7. In a.- device for training operatorsof a radio
40 detection and ranging system, a substitute for the
conventional antenna thereof‘ comprising an’ elec
tromechanical transducer immersed in a liquid
What is claimed is:
1. A training, device comprising a radio detec
tion' and ranging system in which an electrome
compressional wave transmitting medium, said
chanical transducer for transmitting and receiv
transducer’ provided with an acoustic lens for
ingcompressional waves in a comparatively dense 45 broadening the transmission beam of said trans
liquid medium is substituted for the radio an
ducer, said lens being placed normal to the said
beam and having its center‘ of curvature off
2. A training device comprising a tank for
center, and means for rotating said lens about
holding a comparatively dense liquid medium,
an axis coinciding with the axis of the transmis
miniature objects for immersion in said medium
sion beam of said transducer whereby a rotating
at different locations therein, an electromechan
beam of av lobe pattern comparable .to the lobe
ical transducer for transmitting and receiving
pattern of a conventional radio antenna is pro
compressional waves in said medium immersed
therein and av radio detection and ranging system
8., In. a. device for training operators of a split
connected to said transducer, whereby a trainee
lobe radio detection and ranging system, a sub
may be taught the method of manipulating the
stitute for the: antenna thereof comprising an
controls of a radio detecting and ranging device.
electromechanical. transducer immersed in a liquid
3. In a device for training operators of a radio
compressional wave transmission medium, said
detection and ranging system, a complete and
transducer being constructed of a piezoelectric
conventional radio detection and ranging system
crystal having two sets of, electrodes plated there
having an electromechanical transducer for
onfor transmitting two. beams from slightly dif
transmitting and receiving compressional waves
ferent areas thereof and an acoustic lens having
in a comparatively dense medium substituted for
an axis parallel to the axes of said two beams and
the conventional radio antenna, a tank ?lled with
located therebetween. whereby said beams are
a comparativelyv dense liquid medium, said trans_ 65 caused to. become divergent.
ducer being immersed in the said medium and
miniature objects-for immersion in different posi
tionsin'said medium.
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