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Патент USA US3092814

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June 4, 1963
Filed May 1e, 1957
11 sheets-sheet 1
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June 4, ì963
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United States Patent
Patented .lune 4, i963
new or improved method of acoustic position i’inding of
the kind specified Which minimises the risk of losing tar
gets without detection trom an explored sector and which
can be carried out without an unacceptably high degree
of complication as to the apparatus required.
From one aspect the invention resides in the provision
of a method of acoustic position finding of the kind
David Gordon Tucker, Barni Green, England, assigner to
National Research Development «Corpus-ation, London,
England, a British corporation
Filed May 16, 1957, Ser. No. 659,691
Claims priority, application Great-Britain May 16, 1956
21 Claims. (Cl. 340-3)
This invention relates «to a method of and apparatus
speciiied characterized in that the beam is caused to exe
cute one or more scanning sweeps each of continuous
10 movement covering a sector to be explored such sweep
or such sweeps collectively being executed within a time
¿for position iinding utilizing pulses of wave energy, such
interval equal to the transmitted pulse duration starting
as, for example, acoustic wave energy.
at an appropriate time in relation to the emission of a
The term “acoustic” is to be .deemed to include sound
particular transmitted pulse and repeated for a suñ‘icient
waves of any frequency whether above, within or below 15 proportion of the interpulse interval to provide for recep
‘the audible range.
tion of signals reñected from any target within the limit
'Ilhe speciñc embodiment of the invention described
of the range required, the beam width being suliiciently
herein relates to Ia method of and apparatus for acoustic
small to reduce the received pulse duration to a value
position finding wherein a series of time-spaced sound
pulses is emitted so as to travel `from a transmitting sta
tion through a target containing medium a-nd return after
reflection by a target to a receiving station at which the
reliected pulses are received at a beam-forming transducer
providing discrimination as to the period of reception
20 within any scanning sweep, and a further time base swept
in conformity with the scanning sweep of the beam is
utilized in association with the display of the received
pulses to provide determination of target direction.
array and are thereafter displayed on or in relation to a
The beam of the receiving transducer may be caused
range time base synchronised with emission of the trans 25 to execute said scanning sweeps by combining the outputs
mitted pulses to provide range determination of the target.
from respective transducer elements, which are spaced
The term “beam” employed herein in relation to a re
apart in a direction generally parallel to the plane of
ceiving transducer array is used to denote that such array
scan, after passage through phase-shift elements capable
has a sensitivity which varies within a reference plane in
of producing a phase shift of the signal passing there
such a manner that the sensitivity is a maximum in a 30 through, which phase-shift is variable in magnitude in
particular direction, which conveniently may be deñned
response to a change in some electrical condition of opera
by` a reference axis in such plane and which reduces to
tion of the phase-shift elements, so that for a particular
zero or a minimum value at positions spaced angularly
electrical condition of operation the combined outputs
from said reference axis there being one or more such
from the respective transducer elem-ents provide maxi
positions on each side thereof.
mum amplitude of signal for a particular beam position
As a matter of conven
ience and not in a limiting sense the expression “beam
in relation to the reference axis of the transducer array,
width” used herein denotes the angular separation between
those posi-tions at which the output amplitude from the
transducer array is 3 decibels below the output amplitude
and subjecting the phase-shift elements to variation in
said electrical condition orf operation thereby producing
change of magnitude of the phase shift in the signal pass
produced by a signal of the saine strength yfrom a source 40 ing through each such element and thereby producing a
disposed on the reference axis. It will of course be
scanning sweep of the beam.
understood that in the case of a receiving transducer array
the “beam” exists only as a graphical conception con
veniently represented by the polar diagram representing
This form of the method may be carried out in a par
ticularly simple and convenient manner by combining the
outputs from respective transducer elements by feeding
the sensitivity of the array as a function of angular dis 45 them to respective consecutive sections «of a delay line
placement trom the reference axis, whereas in the case
and taking the combined output from one or both ends
or" a transmitting transducer array the ‘thea-m” has some
real physical existence in as much as the intensity or field
strength of the signals emitted by the array is at a maxi
mum `on the reference axis and decreases on each side 50
thereof, the overall phase-shift produced along the length
of the delay line being varied by subjecting it to said
variable electrical condition of operati-on.
It will be understood that it is within the scope of the
thereof falling to Va Ilevel of 3 decibels below the maximum
invention to empl-oy various types of change in electrical
at the limits of the “beam width” as herein defined.
conditions of operation suitable for producing a varia
An acoustic position finding method of the kind here
inbefore specified is known wherein the exploration of a
tion in the phase-shift of the signals passing through the
phase shift elements. For example the phase shift ele
sector of the target containing medium in which a target 55 ments may include inductive components having mag
netic saturable cores and the variable electrical condition
of operation may be constituted by variation of a polariz
ing electrical current, for example a direct current the
value of which determines the effective inductance of
sector to be explored with a suñicient dwell in each posi
tion to permit pulse reflections to be received in that 60 each of these inductive components. Another possible
alternative would be to employ thermionic valves in each
position oci parent transmitted pulses trom a target at the
of the phase shift elements connected as reactance valves
extreme range at which the apparatus for performing this
in a suitable circuit, the reactance being capable of varia
method is designed to operate. One of the disadvantages
tion by the application of a suitable voltage varying as
of this method is that the exploration of the whole sector
may be disposed is performed by mechanical angular dis
placement oi the vbeam forming transducer array, such
angular displacement being performed stepwise over the
takes some appreciable time, and in applications of the 65 a function of time to these circuits.
Preferably, however, variation of the phase-shift is ob
method Where the targets are moving, detection of these
tained by utilization of frequency sensitive phase-shift
may fail to take place because of movement out ot the
elements and by modulating the outputs from the respec
explored area before the beam of the receiving transducer
tive transducer elements with a locally generated variable
array is ‘directed towards the particular position within 70 frequency signal and extracting a single side-band of the
the sector temporarily occupied by the target.
resultant modulated carrier for feeding to respective sec
One object of the present invention is to provide a
tions of the delay line. The term “frequency sensitive” is
feeding the frequency-swept locally generated signal to
used herein to mean that the phase shift produced varies
as a function of the frequency of the signal passing there
the modulators.
FIGURE 3 is a circuit diagram of the output circuit
through. Preferably but not essentially the phase-shift
of a `frequency-swept oscillator providing outputs in quad
rature with each other for feeding to respective modu
is a substantially straight line function of the frequency.
The invention further relates to acoustic position find
ing apparatus comprising a transmitter adapted to emit
lators of the channel.
FIGURE 4 is a circuit diagram of one form of delay
line suitable for use in the apparatus illustrated in FIG
URE l where outputs are taken from both ends.
a series of time spaced sound pulses through a target con
taining medium and a receiver having a beam-forming
transducer array with which is associated an amplifier
means and a display device for displaying pulses received
as reflections from a target, such display being effected
tion of the locally generated signal produced by the cir
on or in association with a range time base synchronized
cuit illustrated in FIGURE 3 and the relationship of this
with the emission of transmitted pulses to provide range
determination of the target.
frequency with the carrier frequency of the incoming
Thus in accordance with a further aspect of the in
FIGURE 5 is la graph illustrating the frequency varia
FIGURE 6 is a graph illustrating the gainI character
istics of the A.G.C. amplifiers in the channels from re
vention there is provided acoustic position finding ap
paratus of the kind specified characterized in that the
spective ends of the delay line to the control grids of
beam of the receiver transducer array is caused to
the cathode ray tube las shown in FIGURE 1.
execute one or more scanning sweeps of a sector to be
FIGURE 7 is a graph illustrating the phase-shift/fre
explored within a time interval equal to the transmitted 20 quency characteristic of the delay line illustrated in FIG
pulse duration by the provision of variable phase shift
elements connected respectively to transducer elements
of the array spaced apart in a direction generally paral
URE 4.
means to provide a combined input thereto which has a
FIGURE 8 is a schematic diagram similar to FIG
URE l lbut showing an alternative form of apparatus in
accordance with the invention' for carrying out the
method thereof utilizing a single beam cathode ray tube
maximum amplitude for a particular phase difference be
tween signals received respectively by the transducer ele
signal extraction from one end only thereof and alter
lel to the plane of scan and connected to the amplifier
ments so as to be characteristic of a particular beam posi
tion in relation to a reference axis lof the transducer ar
ray, and by the provision of means for varying over the
display, a different form of delay line permitting of
native ‘arrangements for modulating the incoming signals
and extracting single side-bands from the resultant modu
ner so coordinated as to swing the beam angularly in
lated carriers.
FIGURE 9 is a circuit diagram of one of the chan
nels connecting -an element of the receiving transducer
'array with a tapping point on the delay line and incor
the plane of scan in relation to the reference axis, the
porating two modulators and a filter all connected in a
duration of each scanning sweep required the phase-shift
produced by each of said phase-shift elements in a man
transducer array providing sufiiciently small beam width 35 series with each other.
to reduce the received pulse duration to a value provid
ing discrimination as to its period of reception within
FIGURE 10 is a circuit diagram of the swept fre
quency oscillator `feeding ‘the second of the modulators
shown in FIGURE 9.
any scanning sweep, and the display device including a
beam position indicating means and a signal reception
FIGURE ll is a circuit of a delay line suitable for
indicating means operable in coordination to provide in 40 employment in the apparatus illustrated in FIGURE 8.
FIGURE l2 is a graph illustrating the relationship be
dication of the position or positions occupied by the beam
upon occurrence of signal reception.
tween the carrier frequency of the received signal, the
fixed frequency of the oscillator feeding the first modu
The phase shift elements may be constituted by con
secutive sections of a delay line and the receiver ampli
lator of the circuit shown in FIGURE 9 and the swept
fier means may be fed from one or both ends of such
line which is so constructed or made up as to permit of
the overall phase shift produced along its length being
capable of variation in response to change in some elec
frequency feeding the second modulator thereof.
FIGURE 13 is a graph showing the phase shift/fre
quency characteristic of the delay line of FIGURE l1.
FIGURE 14 is ia diagram illustrating the reception of
trical condition of operation thereof, and means being
the receiving transducer array of a wave front oblique
to such array and proceeding `from a target- offset from
the reference axis of such array and
FIGURE l5 is a graph illustrating lthe sensitivity of a
single transducer element as «a function' of angular dis
The delay line may have a phase-shift characteristic
which is variable as a function of the frequency of the
placement of signal source from the reference axis and
signal applied thereto and the means for subjecting the 55 sensitivity of the complete array as a function of angular
delay line to said variation in the electrical condition of
displacent from the reference axis, assuming each indi
operation may comprise modulator means adapted to re
vidual eleement to have uniform or non-directional
provided to subject the delay line to such variation over
the duration of each scanning sweep required so as to
produce a scanning sweep of the beam.
ceive signals from respective transducer elements of the
In the following description la general explanation of
receiving array and signals from a local frequency-swept
oscillator and means for extracting a single sideband 60 the manner of operation and identity of the main com
ponents of the two forms of appara-tus illustrated in
from the resultant modulated carrier for application to
FIGURES l and 8 will first be given, the components
respective sections of the delay line.
The invention will now be described by way of ex
ample with reference to the accompanying drawings
FIGURE l is a schematic diagram illustrating the
thereafter being described in greater detail with par
»ticular reference to the considerations which determine
their particular forms and operating characteristics.
Firstly it will be understood that the forms of appa
ratus illustrated in FIGURES 1 and 8 may be utilized
general arrangement of one form of acoustic position
for a variety of purposes wherein it is desired to deter
finding apparatus in accordance with the invention for
mine the position of a tar-get in a `surrounding sound
carrying out the method thereof.
70 transmitting medium, a particular example being the posi
FIGURE 2 is a circuit `diagram of the phase shift net
tion determination of under-water objects such as ships,
works and double balanced modulators contained in one
of the channels connecting an element of the receiving
transducer array with a respective tapping point on the
shoals of fish or even individual fish, and under-water
formations such as the sea bed or obstructions thereon.
The method may, however, be applied in other fields
delay line together with the ampl-itude control units for 75 where for example the target containing medium is not
necessarily a liquid, it could for example be a gas such
as air or of solid form. In the former case the method
would be used for position determination of objects on
the ground or above ground and in the latter case it
would be used for examination or survey of under-ground
formations in which case »the target would be constituted
gain control amplifier (c) will be at a maximum when the
target producing the signal is offset to the left of the ref
erence axis l5 so that the beam is thus deflected angularly
by some object or mass affording a different acoustic im
as hereinafter explained, an angular width equal to the
product of the beam width and the number of transducer
to the left in this case.
In order to scan a sector to be explored disposed sym
metrically in relation to the reference axis 15 and having,
pedance to that yafforded by the surrounding ground ma
terial. Possibly in this Ifield the method may be used in
connection with the position determination of under
elements, or approximately so, the apparatus incorporates
ground liquid `deposits such »as water or oil, or the detec
tion of »liaws or faults in structurees or members of solid
material, such for example -as in ingots or other cast
time the phase-shift produced in the delay line through
each of the sections 13a to 13d without changing the phase
difference between signals fed into the delay line 13 at
In each of the two forms of apparatus a means is pro
vided for emitting a series of time spaced pulses of sound
waves which may be above, below, or within the audible
range such transmitting means comprising a pulse genera
tor 10 the output of which is fed as shown to a transmit
Vting transducer 11 and which is also connected by a lock
ing line to synchronize time base unit 9 forming part of
the display device of the receiver means.
The receiver means which is adapted to receive the
means for varying in a continuous manner with respect to
consecutive tapping points.
These means take one form in the apparatus illustrated
in FIGURE l and another form in the apparatus illus~
trated in FIGURE 8.
In FIGURE 1 the signals fed out from each of the
transducer elements 12a to 12e are passed through chan
nels each containing two branches 16 and 17 in which are
connected respectively a phase shift network indicated at
i651, 16!) etc. and a phase shift network indicated at 17a,
1712 etc. The phase shift networks 16a, 16h etc. are
emitted pulses as refiections from a target comprises a
adapted to produce a phase shift of +45° whilst the phase
beam-forming receiving transducer array which typically 25 shift networks 17a, 17h etc. are adapted to produce a
is shown as having five transducer elements 12a to 12e
phase shift of -45°.
inclusive. This transducer array may be in the form of
The two branches of the channels further contain modu
a strip producing a fan-shaped beam which it is required
lator circuits lâäa, 13b etc. and 19a, 1gb etc. The modu
to swing in a scanning plane perpendicular to the plane of
lator circuits ida and lläb etc. and 19u and 19h etc. are
the beam itself -and in which scanning plane the transducer 30 fed respectively from a frequency swept oscillator 20 pro
elements 12a to 12e inclusive lie. The considerations
viding two outputs in quadrature with each other through
governing selection as to the number of transducer ele
the intermediary of amplitude control units 21a and 2lb
ments are hereinafter set forth.
and the resultant product signals fed from the outputs of
The beam produced by the array 12a to l2@ will nor
the modulator circuits in any one channel, for example
mally be coincident with a reference axis 15 and conse
quently signals received from a target on this reference
axis by the respective transducer elements will be in phase
35 13a and 19a are added to provide a modulator of varying
frequency (the range of frequency being determined by
the frequency swept oscillator) with single side-band mod
with each other. Deflection ofthe beam to one side or the
ulation the phase difference between the signals fed in to
other of the reference axis is, however, contrived by apply
the phase shift networks 16a, 17a etc. on the other hand
ing to each of the signals received from the respective 40 being preserved.
transducer elements 12a to 12e inclusive a phase-shift
The delay line 13 is composed of components which
before the signals are combined with each other the phase
provide a phase shift/frequency characteristic such that
shift applied to the signals from consecutive elements
the phase shift produced along the line varies, conven
12a to 12e inclusive being conveniently but not essentially
iently but not essentially as a substantially straight-line
lsuch that there is an equal phase difference of the same
>sign between the signal received from each element and
the signal received from the element at the right hand
function of the frequency so that the beam position as
“seen” at the output from either end of the line occupies
a position dependent at any particular instant upon the
frequency of the output of the frequency-swept oscillator.
side thereof as seen in FIGURE l. This is done by
The sweep characteristic of this oscillator is arranged
feeding the signals lfrom the respective elements 12a to
12d inclusive to tapping points at the left hand ends of 50 to be of saw tooth form so that there is a continuous
movement of the transducer array beam over the sector
respective sections 13a to `13d inclusive of a delay line 13,
to be scanned, such movement being of approximately
that from the section 12e being fed to the right hand end
constant angular velocity in the case where rectilinear
of the section 13e of the delay line. Thus the output
saw tooth frequency sweep characteristic is afforded by
taken from the left hand end of the delay line i3 to an
automatic gain control amplifier 14a will have maximum 55 the oscillator 2n and the delay line `also affords a substan
tially straight line relation between phase-shift and fre
amplitude when the phase difference between the signals
received at the transducer elements 12a to i’Ze inclusive
`is exactly offset by the phase shift imparted to the signals
by passage through the sections of the delay line 13'. It
fed out from both ends of the delay line 13 is effected
will be evident that the signal from the element i219 will
traverse only the section 13a of the delay line 13 whereas
the signal from the element 12C will traverse sections 13a
and 1Gb of the delay line and will -therefore undergo a
Display of signals received by the transducer array and
upon a cathode ray tube arranged to provide what is corn
monly termed a B-type display.
In the particular ar
rangement of FIGURE l a twin-beam cathode ray tube
22. is employed having two pairs of plates 23a Iand 23h
producing deflections of respective beams in the X direc
greater (for example twice), phase shift in the delay line.
The particular phase shift produced by passage of the 65 tion utilized as a Cartesian coordinate representing an
gular displacement of the beam, and a single pair of plates
signal components from the transducer elements 12a to
12e through the delay line 13 to the amplifier 14a will
thus correspond to a particular beam deflection to the
right of the reference axis 15 since the wave front must
.arrive at the element 12a somewhat later than the time
vof its arrival at the element 12e for the delay line to pro
duce an exact compensation.
2,4 for deflection in the Y direction utilized for range
The outputs from the amplifiers 14a and 1412 are fed
4through video amplifiers 25a and 25b to respective con
trol »grids 26a and 2Gb pertaining to the respective beams
of the tube 22. The amplifiers 14a and 14b incorporate
detector circuits.
Similarly the combined signal extracted from the right
Respective pairs of plate 23a and 23h are fed from a
hand end of the delay line and applied to the automatic 75 push-pull amplifier 29 which is in turn fed from the out
identical in form and manner of operation with those
of the apparatus illustrated in FIGURE 1 and these have
ilar suitably synchronized and phased saw tooth output
been indicated by like numerals of reference.
for both the pairs of plates 23a and 23h of the tube 22
In principle the manner of operation of lthe apparatus
and also the swept-frequency oscillator so that the posi
tions occupied by the two scanning beams of the tube 22 Cil shown in FIGURE 8 is similar to that of FIGURE l
the two main diiferences being that output is taken from
correspond at any instant to a particular frequency of the
only one end of the delay line 30 consisting of sections
oscillator 20 and hence to a particular angular displace
30a to 30d inclusive, the delay line being composed of
ment of the transducer beam from the reference axis 15,
components which in response to frequency change of
whereby it will be evident that the twin beams of the
put of a bearing time base unit 27 which provides a Sim
tube 22 and the beam of the transducer array seen re
the signals applied to the delay line will provide phase
shift range from a negative value through zero to a posi
spectively in the left hand end of the delay line and the
right hand end of the delay line at any instant occupy
tive value and thereby correspond to a complete swinging
corresponding positions along their respective paths of
of the transducer beam from the left hand side of the
scanned sector tto the right hand side.
in the
The other main difference is the manner in which a
ltwin beams of the tube 22 however, are also de
in the Y- or range-direction at a speed which will
in completion of a frame-scan of the tube 22
interval between the emission of one transmitted
single side-band of a frequency swept carrier is obtained
for feeding to the tapping points of the delay line 30
in each of the channels connecting the transducer ele
ments 12a to 12e thereto.
pulse and the succeeding transmitted pulse.
Assuming therefore that both the range and bearing 20 Referring to this last mentioned difference more spe
citically frequency conversion of the carrier of the re
time base are initiated by the leading edge of a trans
ceived signal is effected in two stages, each stage consist
mitted pulse, the first X, or beam direction, scan of the
ing of a modulator and a ñlter. Thus in each of the five
cathode ray tube beams and the ñrst scanning sweep of
channels there are provided modulators 31a, 311; etc. fed
the transducer beam for the reference axis to the extreme
left of the scan section (as seen from the right hand 25 with signals from respective transducer elements and
with a signal from a common fixed-frequency oscil
end of the delay line 13) or the extreme right of the sec
lator 32.
tor (as seen from the left hand end of the delay line)
The resultant product is passed through filters 33a,
will take place in a time determined by the duration of
3319 etc. which pass sum frequencies of the two carriers
the íirst saw tooth of the bearing time base unit output
which in practice have not more than and conveniently is 30 and stop difference frequencies, all carrier leaks, and
side-bands and harmonics of the carrier generated by
made equal to the duration of the emitted pulse. In
the oscillator 32.
practice the bearing saw tooth would be of slightly less
The second or further modulator in each channel as
duration than the transmitted pulse so as to provide for
indicated at 34a, 34b etc. is fed with the sum frequency
ily-back of each of the twin beams of the tube 22 to the
and an output from a swept frequency oscillator 35, the
central axis of symmetry 28 on which the two scanning
resultant product signals being passed through low pass
rasters meet.
filters 36a, 36h, etc. which pass only the difference fre
quency and stop all higher frequencies. In some cases
the filters 36a, 36h as separate entities may be dispensed
As a possible alternative the duration of each saw
tooth output produced by the bearing time base may be
such that the bearing scan on the cathode »ray tube, and a
transducer beam scan, are completed a greater number of 40 with and their functions performed by the delay line
times, for example 2, 3 or 4 during the emission of each
transmitted pulse.
In consequence of utilizing output from the delay line
30 from one end only thereof it is no longer necessary
to use a twin beam cathode ray tube and a single beam
tube 37 is employed wherein as before the output from
The effect of this would be to provide a corresponding
number of successive discrete signals (each being a
sample of the reflected pulse) such signals appearing at
the ends of the delay line 13 and being applied after Ipas 45 the bearing >time base 27 is applied to plates 23 producing
deflection in the X direction to provide beam deñection
sage through the units 14a, 141:, and 25a, 2519 to the con
trol grids 26a, 26h. These signals would all be contained
as a Cartesian coordinate and the output from a range
within a time interval equal to the duration of the trans
mitted pulse so that neither range nor bearing discrimina
time base 12 is applied to plates 24 producing deflection
in the Y direction to give range again as a Cartesian c0
50 ordinate.
tion would be impaired.
The saw-tooth wave form produced by the bearing
The scanning operation of the transducer beam and the
time base is utilized to control the frequency sweep of
cathode ray tube beams are performed continuously and
oscillator 35 and thereby again produce correspondence
thus continue into the inter-pulse interval. In practice the
between transducer and cathode ray tube beam position
scanning continues for the whole of the inter-pulse inter
val but it could if desired be discontinued after a propor
55 so that the brightening of the cathode ray tube spot to
tion of the interpulse interval determined by the maximum
range from which signals are required to be reflected. It
will therefore be evident that received signals fed from
both ends of the delay line 13 to the control grids 26a
and 26h will cause brightening of the spot produced on 60
produce a signal will result in such signal appearing at
a position on the cathode ray tube face corresponding to
the position of the target in the sector explored by scan
ning ofthe transducer beam.
Referring now speciñcally to the particular forms and
operating characteristics of the main components herein
the screen of the tube 22 at a position which determines
before described the pulse transmitter 10 for producing
both the range and the direction of the target producing
such spot brightening.
a time-spaced series of sound pulses may comprise any
suitable form of thermionic valve or other type of pulse
Since the transducer beam sweeps the sector typically
in a time substantially equal to that of the transmitted 65 generator, the detailed circuit of which does not form
part of the present invention.
pulse, it follows that the beam width, being narrower than
The design of such generators is dealt with in the book
the sector to be scanned, will receive only a Vertical sec
“Waveforms” (vol. 19 of Radiation Laboratories Series)
tion or sample of the pulse reflected from any target,
section 4.13 published by McGraw-Hill Book Oo., Inc.
the width of this section or sample being dependent upon
the beam width which is thus made sufficiently small 70 to which reference may be had for further details.
It ‘is indicated by way of example that a carrier fre
to provide discrimination of the required order as to
target direction on the display produced on the screen of
the cathode ray tube 22.
In the alternative form of apparatus illustrated in FIG
URE 8 certain components thereof may be substantially
quency for the sound waves to be emitted of 50 kc./s.
may be employed the pulse duration being typically 1000
microseconds and a repetition frequency of about 1 pulse
per second provide for the reception of reflected signals
from targets submerged in water up to an extreme range
of about 800 yards.
These figures are given as typical of those which may
be utilized in practice and it is to be understood that
they do not limit the scope of the invention which is
hereafter defined in the claims.
The transmitting transducer il fmay likewise be of
known form. Any one of the three main types namely
magnetostriction, piezoelectric, or electrostriction (for
example barium titanate may be used). Further details 10
relating »to these devices may be obtained by reference
to publications of which the following are typical:
Curve (a) in FIGURE 15 represents factor (a) and
curve (b) in FIGURE 15 represents factor (b).
It will thus be evident from FIGURE 15 that when
there is no phase difference between the signals received
by respective transducer elements (that is to say when
the target is disposed on the reference axis and the wave
front is parallel to the length of the array) the secondary
peaks of the curve (b) which occur at values of 0 given
will not produce any signal in the transducer element
(l) “Ultra-sonic Engineering” by A. E. Crawford,
published by Butterworth & C0., London, 1955.
(2) “Fundamentals of Electro-Acoustics” by F. A.
Fischer (translated by S. Ehrlich and F. Pordes) pub
lished by Interscience Publishers, New York, 1955.
(3) “Quartz Vibrators,” by P. ‘vigoureux and C. F.
hence the resulting product is zero.
When, however, the beam is deflected by the use `of
Booth, published by HM. Stationery Office, London,
represented by curve (b) which is so deflected whilst
because curve (a) falls to a zero at these positions and
a delay line l?, or 30 as previously described this con
dition is modiñed because it is only the diffraction pattern
clearly the directivity pattern of the individual transducer
elements as represented by curve (a) remains undeflected
by the delay line. Thus as deflection by the delay line is
in consequence of the emission of the transmitted pulses
increased two effects take place:
should be uniform throughout the sector and fall to zero
(l) The main peak of diffraction pattern curve (b)
or a low value at the boundaries, but this condition is not
capable of exact attainment.
25 diminishes in accordance with the charactistic represented
by curve (a) and
However, it is preferred not to use a transmitting trans
(2) One of the secondary peaks of the curve (b)
ducer element which would operate in effect as a point
will increase according to the characteristic represented
source and thus produce all round emission because this
by the curve (cz).
would produce undesirable ambiguities, arising from the
Thus when the main peak has been deflected by an
existence of side lobes in the polar diagram afforded by
the receiving transducer array, and in practice the trans
mitting transducer may consist of a strip array of trans«
Ideally the energization of the sector to be explored
ducer elements with an excitation related to the distance
lx from the centre of such array by the expression:
excitation=l+2 cos xn
where x is zero at the centre of the array and unity at each
end of the array.
the resultant amplitudes of the main and a secondary
diffraction peak are equal, and upon further deflection
the secondary diffraction peak exceeds the main peak so
as in the effect to replace the main peak.
This has a directional pattern which is uniform to
Thus no useful deflection of the beam by means of a
about i3% of amplitude over an angle from
40 delay line beyond an angle
sin 1
where k is the wave length of the carrier and l the length
is possible and such deflection is limited accordingly to
of the strip array.
avoid secondary diffraction peaks corresponding to first
Referring now to the receiving transducer array the 45 order side lobes in the polar diagram of the array be
transducer elements themselves may be of any or" the
coming operative to cause ambiguities through attaining
types previously mentioned. Careful consideration needs
a gain of the same order as that of the main diffraction
to be given to the form of the array namely the number
peak corresponding to the main lobe.
of transducer elements utilized and the effective length of
The limit of the scanned sector to be explored is thus
the array.
In this respect it is convenient to refer to the directivity
pattern of the individual transducer elements, and of a
strip array wherein the elements are spaced apart from
each other in a direction perpendicular to the reference
Since n is only the Variable (assuming that A and l are
55 fixed by other design considerations) an increase of
axis and in the plane to be scanned.
The directivity pattern is the product of two factors,
scanned sector necessitates an increase in the number of
these being:
sub-divisions of the receiving transducer array and a
(a) the directivity pattern of the individual transducer
consequent increase in the number of channels necessary
elements represented by the expression:
between this array and the delay line.
Since a beam width (between half-power points ap
proximates to an angle of
where a' is the length of an individual transducer element 65 it will be evident that the maximum scanned sector can
and 0 is the included angle between .a Wave front arriving
conveniently be expressed as approximately ‘n’ times the
from a target offset from the axis of symmetry and the
beam width provided the angles concerned do not exceed
length of the array as seen particularly in FIGURE l5.
say about 45 °.
(b) the diffraction pattern of ‘n’ point transducer ele
Referring now to the channels feeding the signal
ments spaced apart from each other by a distance ‘d’ 70 from the transducer elements 12a to 12e to the delay
given by the expression:
1 6)
sin 9)
line 13 these are illustrated in greater detail in
The phase-shift net works 16a, leb etc. and 17a, ¿7b
etc. comprise respectively series connected condensers
Cl and C2 and cross connected inductances L1 and L2 in
Colpitts oscillator would be suitable, this being designed
the ñrst case and series connected inductances L3 and
L4 and cross connected condensers C3 and C4 in the
These networks are well known and the
to provide an output at a fixed frequency of 3.525 mc./s.
(for a transmitter carrier frequency of 50 kc./s. as pre
further explanation as to their manner of operation and
viously described by way of example). Further details
design may be had by reference to “Radio Engineers’
Handbook” by F. E. Terman, published by The Mc
lators including the Colpitts type may be had by reference
Graw-Hill Book Company, Incorporated, New York,
1943, page 247.
For an input signal to these networks received from
“Radio Engineers’ Handbook,” by F. E. Terrnan, scc
tion 6, page 480, particularly figure lb.
an associated element of the transducer array of the 10
general form cos (gt4-0) the outputs from these networks
considered relatively to each other may be represented
An output from a swept frequency oscillator is applied
to terminals 39. The swept frequency oscillator may be
as shown in the circuit diagram of FIGURE l() (to be
by expressions
hereinafter described) and designed to provide a frequen
second case.
as to the design and manner lof operation of such oscil
cy sweep from 3.600 mc./s. to 3.675 mc./s. as a substan
15 tially linear function with respect to a time over the
cos (qto-l-û-ë) and _sin (qta-i-H-TT)
form comprising respectively input and output trans
duration of a transmitted pulse for example of 1000
The swept and fixed frequency `outputs are combined
(multiplied) in a modulator circuit comprising input
transformer T5, rectifiers W9 to w12 `and output trans
former T6 the product being fed from the secondary of
formers T1 and T2 for 18a and T3 and T4 for 19a and
rectiñers w1 to w4 inclusive for 18a and rectiñers wS
to w8 inclusive for 19a.
the transformer T6 through a low pass filter to output
terminals 40.
Signals from the two oscillators are further combined
which outputs are applied respectively to modulator
circuits 18a and 19a.
These modulator circuits are in themselves of known
The manner of operation and design details of these 25 (multiplied) in a further modulator comprising input
modulator circuits which are generally termed “double
and output transformers T7 and T3, and rectifiers w13
balanced ring modulators” may be had by reference to
to w15» after passage of the frequency swept signal through
“Modulators and Frequency Changers” by D. G. Tucker,
a phase-shifting network comprising in‘ductances L5 and
published by MacDonald & Co. Ltd., London, 1953, par
L6 `and cross connected condensers C7 and CS.
ticularly chapter 3, section 1.1.
The secondary windings of the transformers T2. and
T4 are appropriately terminated by resistors R1 and R2
The secondary winding of transformer T3 is connected
through a low pass filter to output terminals 41.
It will be evident that at the terminals 40 and 41 there
and the output from the channel is taken from one end
will appear difference frequency signals differing in phase
from each other by 90°, the difference frequency ranging
of these two resistors, the other end being earthed as
The feeding of the signals from the two outputs (in
from 75 kc./s. to 150 kc./s.
The table below shows suitable values for the com
ponents of the circuit:
quadrature with each other) from the frequency swept
oscillator 20 is effected respectively through the amplitude
control units 21a and 2lb each of which conveniently
comprises a variable-mu valve as indicated at V1 and V2 40
R7, RS, R9, R10 ______________ __ohms__
respectively, the control grids whereof are fed with an
inverted saw tooth signal from the range time base unit
R11, R12 ____________________ __do____
C7 and C8 ______________ __microfarad__ 0.00044
12 so that the gain decreases -as a suitable function of
C9, C10, C11, C12 ____________ __-do____
time, being at a minimum for the extreme ranges.
L5 and L6 ____________ __microhenries__
L7 and LS _______________ __millihenry-_
Signals received by the receiving transducer array
from extreme ranges are of course 0f substantially
Referring now to the delay line 13 a circuit diagram
smaller amplitude than those received from nearby
of this is shown in FIGURE 4. Such delay line provides
targets, but the operation of the amplitude control units
a positive phase shift of signals applied at the tapping
21a, 2lb provides an approximately constant ratio of
points with respect to the phase at which they appear
amplitudes between the received signals fed into the two
ring modulator circuits 15a and 19a and the swept-fre 50 at either end of the line so that it is necessary to take
outputs from both ends of the line to produce a sweep
quency carrier signals fed into these circuits from the
of the transducer beam on each side of the reference
axis 1S. It will of course be understood that an arrange
ment wherein an output is taken from yonly one end of
Typical values and types for the components of the 55 a delay line of this kind can be utilized in which case
there will be a sweep of the `transducer beam to only
amplitude control units are given in the table below*
one side of the reference axis 15 with a similar reduction
swept frequency oscillator, these latter signals preferably
predominating slightly over the received signals at all
Type or value
in the angle of the explored sector.
Enlargement of
this angle could of course be attained by utilizing a great
R3 _________________________ __ohms__
R4 _________________________ __do__„_ 10,000 60 er number of transducer elements and hence a greater
number of delay line sections, but this would entail in
R5 _________________________ __do____
creased complication due to the multiplication of the
R6 _________________________ __do____ 10,000
number of channels incorporating modulators and phase
C5 ___________________ __microfarads„_
shift networks.
C6 __________________________ __do____
_________________________________ _..
V2 _________________________________ __
Referring to FIGURE 3 there is therein shown a
circuit diagram of an output circuit providing the two
Assuming that the delay line affords `a total phase shift
from one end to the other of q>T radians then the beam of
the transducer array will have its axis deflected from its
normal direction by an angle of approximately
outputs (in quadrature with each other) from a frequency 70
swept oscillator suitable for employment as the frequency
swept oscillator 20.
The output from a ñxed frequency oscillator is ap
radians where A is wave length of ythe received carrier
plied to terminals 3S. The fixed frequency oscillator
and l is the length of the transducer array. This ex
may be of any suitable known type, for example a 75 pression assumes the angle of deflection to be small and
the number n of sections in the transducer to be large
the design `of ampliiiers suitable for the video ampliñers
25a and 25h.
Component values for a delay line having the circuit
since more strictly the deñection is
- -1 if@
(ad zal
shown in FIGURE 4 and suitable for use with a received
signal carrier frequency of 50 kc./s. and a total scanned
sector equal to 5 times the beam width are given in the
table below---
When qST equals 1r the angle of deflection of the trans
ducer beam is
and assuming that all transducer elements -have the same
sensitivity and that 4the transducer array is untapered
along its length, then the directional pattern of the beam
at an angle of
from the direction of peak response has an amplitude
which is approximately 273 that of the peak, and it is
therefore convenient to consider that the value of «15T 20
equal to 1r detlects the beam by about one-half of the
beam width, although this is only an approximation of the
3 decibels beam wid-th assumed from the foregoing delini
. tion thereof.
As has been previously explained variation of ¢T is
obtained by use of a frequency sensitive delay line.
Whilst there is flexibility in the selection `of frequencies
a suitable arrangement is illustrated in FÍGURE 5 which
shows a frequency sweep from 3è q to (1-l-k)q completed
in the time of the lsweep of the bearing time base where
the general form of the carrier of the received signal is
cos (qf-l-H).
Thus the frequency applied «to the del-ay line is equal
to 1/2 q at the beginning vof the sweep and Icq at the end
as illustrated by the full line in FIGURE 5.
lf the phase-shift/ frequency characteristic of the delay
line is linear or substantially so (as will be the case as
-Clîib to C13d ________ __micromicrofarads-Cléa to Clad __________________ _„\do____
C1Sa to Cìâd __________________ __\do__-_
Clöa to Clad __________________ __do_„__
Cll’ïa to C17d __________________ __do____
`C13a and CiSe _________________ __do____
Lida to Lit'id ____________ __microhenries__
Lida to Lied __________________ __do____
Lilia to Lila' __________________ __do____
L12a to L12d __________________ __»do____
L13a to Llâd __________________ __do-___
L9!) to L9d ____________________ __do____
L95: and L95: ___________________ __do_-__
The range time base unit 9 and the bearing time base
unit 27 as well as the push-pull amplifier 29 through
which the output from the later is fed to the pairs of
plates 23a and ¿3b may be of any suitable known vform,
the design of time base units and amplifiers for this
purpose being well understood by those skilled in the
art. A publication to which reference may be made in
30 this connection is “Principles of Radar” by Reintjes and
Coate, particularly chaper 3 thereof published in 1946 by
McGraw~Hill Book Company, incorporated, New York.
It will be understood that the cathode ray tube 22
may be of any suitable type providing a twin beam dis
play and incorporates a single pair of deiiection plates
24 (of which one is visible in the schematic diagram of
FIGURE 1) these plates being connected respectively t0
the output terminals of the range time base whilst the
tube incorporates a shown separate reflection plates 23a
and provides a total phase shift ¢T tof 21|- at a yfrequency
and 23h and separate control grids 26a and Zeb for re
q then the transducer beam will be «deflected by half a
ceiving the outputs on the video ampliñers 25a and 25h.
beam Width at the beginning of the sweep and the de
Range information is produced on the cathode ray
flection will increase continuously and smoothly to a
tube 2.2 as the value of the “Y” co-ordinate at which a
maximum 'of k beam widths at the end of the sweep,
bright spot is produced on the face of the tube in con
the cycle then being repeated in consequence of the
repetition of the linear saw tooth frequency variation 45 sequence of received signal applied to the control grids
26a, 26h, thereof. It will be understood that beam de(p-q) as shown by the full line in «FIGURE 5. The
ñection in the “Y” direction is produced by the range
phase shift/ frequency characteristic `of the delay line is
time base unit 9 furnishing a linear (or other desired
illustrated graphically in FIGURE 7 wherein the phase
form) of saw-tooth voltage output synchronised with
shift qbT is the yordinate and the frequency is the abscissa.
It will Ibe evident therefore that at the beginning of 50 the pulses emitted by the transmitting transducer 11 by
a locking signal fed from the pulse generator to provide
the sweep the transducer bearn is not coincident with
sweep of the cathode ray tube beam in the “Y” direction
the reference axis 15 but is in yfact deñected by an angle
starting at an instant corresponding to Zero range and
equal to half a lbeam width to the left ot the reference
terminating at an instant corresponding to the maximum
axis 15, as seen from the right hand end of the delay line,
range required, the time interval between these two
and to -the right of the reference axis by half a beam
instants being the transit time of a radiated sound pulse
width as seen from the left hand end of the delay line.
travelling from the transmitting transducer 11 to a target
Signals received from targets disposed on the reference
at extreme »range and, after reñection therefrom, back to
axis are thus indicated by coincident vpresentation of
the receiving transducer array 12a to 12e. Any suitable
signals of 273 amplitude from both `left hand and right
hand scans of the transducer beam and ycathode ray tube 60 form of range calibration may be provided or in associa
tion with the cathode ray tube 22 or range tube base
beams and since this arrangement would give a somewhat
unit 9.
excessive response to targets positioned on the reference
Referring now speciiically to the particular forms and
axis 15 the Kgain of the amplifiers 14a and Mb is reduced
operating characteristics of the main components of the
between frequencies of q and 1/2 q as illustrated in FIG
URE 6 wherein gain is plotted as ordinate and frequency 65 alternative form of apparatus illustrated in FiGURE 8
which dider from those already described in detail in
as the abscissa. .These ampliiiers also incorporate de
connection with the apparatus illustrated in FÃGURE 1
tector circuits.
reference is made firstly to the channels which connect
The V»design of such ampliiiers is well known in the art
the respective transducer elements 12a to 12e inclusive
and reference may be had for further details to:
“Vacuum Tube Ampliñers” by Valley and Wallman, 70 to their tapping points on the delay line 30.
The resultant signal which emerges at the output end
volume 1S of The Radiation Laboratory Series, published
of each of these channels to the delay line is of a form
by The McGraw~Hill Book Company, Incorporated, New
similar to that already described in connection with FiG
York, particularly the sections thereof ‘dealing with stag
snming adoption of the circuit illustrated in FIGURE 4)
gered tuned ampliners and gain control therein.
URE 1 in as much as it consists of a single side band
Reference may also be had to this publication as to 75 of a swept frequency (being the di‘lïerence between the
carrier frequency of the received signal and a locally
generated swept frequency carrier) but the manner of
attaining this result is different as is also the treatment
of each of these signals in the delay line itself, the latter
having a value at any instant of p-l-u where u is a func
tion of the bearing time base output voltage represented
by 0;(1‘).
The low pass filter 36a will pass only the difference
component p-l-q-S-i-Lda), as indicated by the line 44
being such as to provide a sweep from a negative phase
shift to a positive-phase shift as seen at one end of the
which has a frequency range as shown determined by the
line thereby avoiding the use of a twin beam cathode
ray tube and duplication of the :amplifying and detection
channels and bearing time base unit and associated ani
upper and lower limits of the frequency of the output
from the swept frequency oscillator 35.
One of the channels consisting of modulators 31a and
It should be noted that the overall range of the fre
10 quency sweep may be less nq (where n is the number of
34a and filter 33a is illustrated as a circuit diagram in
beam widths contained in the scanned sector) but it
should be larger than
FIGURE 9 the principle of modulation utilizing the so
called (transformerless modulators) being discussed more
fully in “Modulators `and Frequency Changes” by D. G.
Tucker particularly chapter 3, section 1.4, published by
(Where f is the pulse duration in seconds and the band
width is measured in cycles per second) if excessive dis
MacDonald & Co. Ltd., London, to which reference may
tortion is to be avoided.
be had for a complete explanation.
Such distortion would tend to arise if the frequency
The first modulator comprises valves V3 and V4 the
former receiving on its control grid a signal from the 20 sweep were narrow compared with the pulse spectrum
fixed frequency oscillator 32 and the signal from the trans
ducer element, in this case 12a, being fed as shown into
the anode-cathode circuit of V3 the resultant sum and
difference components appearing at the control grid of
V4 which Iacts as a cathode follower applying signals to 25 because the different frequency components of such spec
the input terminals of filter 33a.
trum would be subjected to greatly differing phase-shifts
The latter is designed in this particular example as a
in the delay line.
high pass filter to pass the difference component and
For a received signal carrier of 50 kc./s. the fixed fre
stop the sum frequency and all carrier leales and side bands
quency oscillator may generate a signal having a fre
of harmonics of the fixed frequency, but equally well 30 quency of 1.05 mc./s. and the swept frequency oscillator
the filter could have been a bandpass filter passing the
a frequency varying from 3.165 mc./s. to 3.675 mc./s.
sum component and rejecting the difference frequency
Suitable values of the components of the circuit of FIG
and all carrier leaks etc.
URE 9 for these frequencies are set out in the table below:
FIGURE 12 is a graph illustrating the operation of the
circuit wherein frequency is plotted as the ordinate and
R12a ____________________________ __megohm__
time as the abscissa.
R15 _
_ohms__ 220
R16 ________________________________ „_d0--__ 220
is fed to the control grid of a correction amplifier afford 40
anode-cathode circuit of the second modulator 34a which
incorporates valve V6 to the control grid of which is
supplied the variable frequency input from the frequency
1 >
R13 _____________________________ __kilohms-- 2.2
R14 ________________________________ __do..___ 2.2
The frequency of the fixed frequency oscillator is S,
and the component S--q is represented by the line 42.
The difference component from the high pass filter 33a
ing variable gain comprising the valve V5 and associated
circuit, the output of this amplifier being fed to the
R17 _________________________ __ Potentiometer ohms
45 R22
swept oscillator 35.
________________________________ __ohms__
_____________________________ ~~kilohrns~_______________________________ __ohms-________________________________ __do____
_____________________________ __kilohrns-..
R23 _
The purpose of the correction amplifier is to com
pensate for the fact that the delay line 30 does produce
some attenuation of the signals fed thereto at the various
tapping points before these reach the right hand end of 50 R27
the delay line, and such attenuation will be greatest in
___do____ 470
________________________________ __do_..__ 5.6
________________________________ __d0„___ 2.2
________________________________ __ohms-- 160
_____________________________ __kilohrns-- 60
_____________________________ __megohm-1
respect of the channel associated with the transducer ele
kilohms-- 2.2
ment 12a and have a correspondingly smaller value pro
R30 ________________________________ __do___.. 2.2
gressively for the channels associated with the elements
R31 ________________________________ __ohms-- 220
12b to 12e (being Zero for the last mentioned) having 55 R32 ________________________________ __do____ 220
regard to the fact that signals from the channels associ
R33 ________________________________ __do____ 620
ated with these elements pass through a lesser number
C18 _________________________ __microfarads-- 0.01
of sections ‘of the delay line. 'Ihe gain of the correction
_______________________________ __do-__.. 0.01
______________________________ __do____ 0.002
______________________________ __do...~ 0.01
___________________ __micro-microfarads__ 178.5
______________________________ __do____ 1190
______________________________ __do____ 178.5
________________________ __microfarads__ 0.002
______________________________ __do-___ 0.01
______________________________ __do____ 0.02
______________________________ __do____ 0.01
ampliler for each channel is thus adjusted (for example
by selection of suitable valves `for R22 and R23) to 60
compensate for the unequal attenuation of the signals fed
from the several channels through the delay line.
The particular form of delay line of which the circuit
is shown in FIGURE 11, has stop characteristics at the
upper end of its pass band which are adequate to obviate
the necessity for providing a separate low pass filter in
each of the channels connecting respective transducer
elements to their respective tapping points.
However, it will be understood that in other circum
stances such filters might be required and the component 70
values thereof in this case would be selected in a manner
well understood by those skilled in the art.
The input from the swept frequency oscillator to valve
V6 of the second modulator is shown by the line 43 in
the graph of FIGURE 12, the frequency of this output
do____ 0.001
C30 ______________________________ __do____
C31 ______________________________ __do____
________________________ __microhenries__ 121.8
______________________________ _1do____ 121.8
_______________________________ __do-___ 52.3
_______________________________ ..„do_-.... 52.3
'1 7
V3 __________________________________ __ Type 615
lustrated by FIGURE 12 the frequencies indicated by the
V4 ___________________________________ __Type 6)'5
dotted lines 45 and 45 will correspond to the lower and
V5 ________________________________ __ Type 6AC7
upper limits respectively of the frequency sweep `44 in
___ Type 615
The fixed frequency oscillator may be of the Colpitts
type and details as to the design and manner of operation
may be had .from the publication referred -to in connec~
tion with the ñxed frequency oscillator employed in the
circuit arrangement of FIGURE 1.
A suitable circuit for the swept frequency oscillator is
Fora single side-band signal ranging from 2.165 mc./s.
to 2.675 mc./s. component values suitable for employ~
ment in the delay line 30 are as follows:
-R34a `to R34@ ____________________ __kil'ohms--
illustrated in FIGURE 10 wherein V7 is connected to op
erate as aV reactance valve and receives on its grid a posi
tive-going saw toothed wave form from the bearing time
base unit.
The manner of operation of reactance valves is well 15 C3‘7a
understood but reference may be had if desired to “Radio
Engineers’ Hand Book” by F. E. Terman, section 9, pub
lished «by McGraw~Hill Book Company, Incorporated,
New York.
L19a and L19e _______________ __micr-ohenries-This reactance valve is connected across the divided 20 L19!) to L19d ______________________ __do____
capacity constituted by condensers C44 and C45 of V8
which constitutes the oscillator valve, the output from the
oscillator being fed to ta valve 9 connected as amplitude
limiter operation of which is yagain well understood but to
which reference may be had in section 6, paragraph 6, of 25 L22a
the last mentioned publication, and for an output valve
The table below shows ksuitable component values for
the circuit:
R35 _____________________________ __lm'lohms-R36 ____
do____ 470
R37 ________________________________ __do____
R33 _____________________________ __megohm__
R39 _____________________________ __k-ilohms__
yand (232e __________ __micro-m-icrofarads__ 175.5
to C32c _______________________ __do____
and C313@ _____________________ __do____ 38.8
to C33d _______________________ __do____ 77.6
tto C34d ______________________ __d0____ 590
‘to C3’7d ______________________ __do____ 590
to CSSd _______________________ __do____ 25.7
to Cîßäd ______________________ __do____ 25.7
to C36d _______________________ __do____ 20.6
yto LZtid _______________________ __do____
to L23d _______________________ __do____
to L21d _______________________ __do____
to L24d _______________________ __do____
to L22d _______________________ __do____
and L25e ______________________ __do____
to L25d _______________________ __do_-__
It will be understood that the form of channel con
necting each 'transducer element with a tapping point on
the delay line as described with reference to FIGURES
8 to 12 may be employed with a delay line of the kind
described and illustrated with reference to >FIGURES 1
to 5 >in which case a twin beam cathode ray tube will be
20 35
_______________________ __ ______ __ohrns__. 220
required for display purposes. Alternatively the form of
channel described `and illustrated with reference to FlG
R41 _____________________________ __kilohms__ 100
URES l to 5 may be employed with a delay line of the
R42 _____________________________ __rnegohm-l
kind shown in FIGURE 1-1 in which case output will be
R43 _____________________________ __kilohms__ 470
taken from one end only of this delay line and a single
R44 ________________________________ __do____
20 40
beam cathode ray tube utilized for display.
R45 ________________________________ __\do____ 30
R46 _______________________________ __ohms__ 220
R36a _______________________________ __do____ 220
What I claim is:
1. in a position find-ing apparatus comprising a trans
mitter for emitting a series of time-spaced pulses of wave
C39 ____________________ __micro-microfarads__` 700 45
C40 _________________________ __microfarads__ 0.02
C41 _______________________________ __do____ 0.02
means, and a display device having means for position
C42 ____________________ __micro-micro-fara-ds__
said amplifier means of a receiving beam-forming trans
ducer array comprising spaced transducer elements con
C44 ____________________ __inicro-microfarads__
150 50
_____-_ _________________________ __do____
nected with respective signal channels feeding said am
plifier means, means for generating a local signal varied
_________________________ __microfarads__
_______________________________ __do____
_______________________________ __do____
_______________________________ __do____
_______________________________ __do____
____________________ __micro-microfarads--
_________________________ __microfara
energy through `a target containing medium, amplifier
ally indicating signal reception; the combination with
through a range of values within a time interval equal
to the duration of each of said emitted pulses and re
peated a plurality of times Within each pulse repetition
0.02 55 period, phase-shift elements in said channels responsive
to each instantaneous value of said local signal within
said range to impose respective phase shifts of differing
__. 0.02
C52 '__ _____________________________ __do____ 0.02
C53 _______________________________ __do____ 0.02
C54 _______________________________ __do____ 0.02
magnitude in each channel and hence to determine the
relative phases of signals arriving at said amplifier means
and thus to determine the angular position of »a beam
formed by said array in relation to a referenct axis
thereof, means for coordinating variation of said local
V7 ___________________________ __ ____ __ Type EF89
V8 _________________________________ __ Type 5F91
V9 ________________________________ __ Type EAS()
signal with said means of positionally indicating4 signal
zero so lthat as seen from the right hand end of the line
the transducer beam would appear coincident with the
ally indicating signal reception; the combination with
of the delay line having a frequency characteristic as il
nected with respective signal channels feeding said tam
reception and means for tapplying salid local signal to said
phase shift elements to swing said beam through a sector
V10 _______________________________ __ Type EF91 65 of said target containing medium in said time interval
and for a corresponding number of times within each
Referring now to the delay line âû’this is composed of
pulse repetition period.
four sections providing as seen from the right hand end
2. In a position `finding apparatus comprising a trans
of the line a phase shift which is illustrated graphically
in FIGURE 13 wherein phase shift d is plotted las the or 70 mitter for emitting a series of 'time-spaced pulses of wave
energy through a target containing medium, amplifier
dinate and frequency as the abscissa.
means, and a display device having means for position
At a mid-value of the frequency range phase shift is
said -ampliñer means of la receiving beam-forming trans
reference axis l5; For input signals to the tapping points 75 ducer array comprising spaced transducer elements con
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