US2943322A - Directional wave energy receiving system - Google Patents

Description

3 Sheets-Sheet 1 G. F. ASBURY, SR

DIRECTIONAI.. WAVE ENERGY RECEIVING SYSTEM Filed Dec. 8, 1952 June 28, 1960 IIIZP l l l l llllv INVENTOR G EORGE F. AS BURY,.SR

(bg J- ATTORNEY5 June 28, 1960 G. F. AsBURY, SR 2,943,322

DIRECTIONAL WAVE ENERGY RECEIVING SYSTEM Filed Dec. 8, 1952A 3 Sheets-Sheet 2 |NPuT i 'ioUTPlT l 42 I l K i I 43 V55 Elil L HP? l l i |31 l L VARIABLE 5h 6M PHASE SHIFTER I swEEP F'XED oscILLAToR i vAR|ABLE I I DELAY l DQ/ I I OUTPUT FRo v| al FROM e2 INVENTOR BY i l ATToRNEY June 28,A 1960 G. AsBuRY, sR

DIRECTIONAL WAVE ENERGY RECEIVING SYSTEM Filed Deo. s, 1952 3 Sheets-Sheet 5 3o 9o |50 21o 27o 33o VARIABLE v ZOSN DELAY VARIABLE INVENTOR GEORGE F. ASBURYSR.

@{vll I ATToRNEYs This `invention-relaties-'to -wavefenerg-v receiving'xsystems'.

nitedStat-es Patent] More particularly it relates-toa directional wave energy receiving system wherein vthe `direction'of optimum reeeption of the :receiving-.system-can be scannedthrough 3 6G- or' azimuth without mechanical movement of the wavesignal receiving array.

ilt is an.-objectl .of this invention to provide a signalfreceiving system which -is exclusively vresponsive .tozsignals received from-a selected directional zone.

It is another object .to provide a directional .receiving system in` which the direction from which .signals-are selectively -receivedcan `be -varied through 360 -of azimuth without physical movement-.of -the signal receivin'gmeans.

fit is another object` to 'provide-,a .receiving system in which the directiontrom` whichsignals are selectively received `can be varied at a station :remote from the signal receiving means. v -H It is anotherv object -to--providea receiving vsystem-rin which the direction .from which signals `are selectively received can be varied by selectively adjustingethe time relationship of received signals in a: predetermined-,man- 11er.

It is another object to provide a receiving .system in which the width of the selected directional zone of reception can be varied independently of the .frequency of rei ceived signals, ata station. remote from the signal receiving means.

These and other objects and features ofthe-present invention will appear more fully .hereinafter from the following detailed description considered in connection-withy the accompanying drawings, which disclose one-embodiment of the-invention. It is expressly understood, how` ever, that: the drawings are designed for purposes of illustration only and not asadeinition ofthe limits' of the invention, for which referenceshould'be hadto thevappended claims.

In the drawings:

Figure 1 is a schematic blockdiagram of a receiving-` system constructed in-accordancewith the present-inven tion.

Figures 2, 3' and 5 are schematic. diagrams ofportionsoi the system shown in- Figuregl. v

Figure 4 is a graph useful inl explaining the operation of this invention.

Brieily, theV presentinvention provides 'means for-.receiving selectively only signals whose arrival-times-at threetriangularly disposed `receiving elementsbear a particularselected relationship. Specilically the signals arriving. at the three elements are-delayed-by varying-amounts `of time as necessary to bring-them-.into coincidence,- the varying amounts of delay required providing, a measureof the received signal direction ofarrival. Moreover,.

time delays imparted lto-signals-received4 by each-ofthethree receiving elements` can be varied relative 'to-one:`

another` in an orderly mannerto vary smoothly the'idirecf tion f from which .signals-k are selectively received,. s"o thateifectively 360" of."` azimuth can bef scanned withoutf any.`

physical rotation of the receiving element array, by

2,943,322 Patented "June 28, i960 a ce A"riierly varying 'thetime 'delay Va"ss-ocia'ted 'with each re- 'angle ABC' should not be longer 4than one wavelength ofV vthehighest frequericyl4 signal to he received, lirl-order to avoid'a'rribiguitiesin processingthe received signals, as 'will be apparent hereinafter. With the, three receiving elements ,'so oriented itlv'vill be-*ap'parent that it is possible to ascertain the orientation'of the wavefront of anyV sig'- nal intercepted by uthe 'receiving "array by measuring the relative times of 'anivalfof thereceivedsignal at the three dil'erent elements. YConversely:byrecovering from all the signals intercepted by the three-element array 1,` only those sign-als which arrive at the diieren't elements: A, BY and C 'in-a preselected time relationship, itis possible to recover selectively 'only signals Ywhose wavefronts 'have aparticular selected orientation, ie., Vvv'ljiich "arrive from a'particular selected tii'rectionfor bearing; For example, it-'vw'ill "be apparent that a signal which arrives first at element A, Vand I ater arivessimultaneously at elements B'v 'and C, 'comes froma direction dened by 'a line 'be tween'the'cen'ter Oofthe't'riahgle and element A, and fit isl possible to recover selectively onlys`i`g`n`alsjfromthis direction by Y'recovering only 'signals` whose l"arrival `times at the"three-receiving-elements are sorelated. Y n u Signals intercepted the receiving array 1 are corrveyedihrough v`av common communication link 4, such as a radio link or r'e transmissionilin, 'tothe remainder of the 'gtial receiving 'system which may be located;at v'a statio emote ffroin thereceivingl array. Fromthe output of theA E:om'muiii'c'atic'ml liirk 44, Ithe' signal from receiving element is fed through` amplifier 5 to a-pulse generator 6; In pulse generator 6 the received signal'is converted to' the form of a train of pulses, 4one for eachfcycle of the receiver signal. Purse gent-rami; `s may be or any conventional form, capable of generating a pulse at the saine point'in each cycle of `aV wavetrain signal, for 'example, a s'at'rable reactor.V 'Ihe'output pulsesy fromY pulse generator 76' are-fed to a pulsewiden'er 7, which for ekar'nple- 'may be ja conventional one-shotr'n'ultivibr'ator, in which'- theY widthv`of the individual pulses' is `converted tov a uniform selected value for subsequent utilization as will be `explained hereinafter.- 4

Signals from receiving elements B and C are processed' in' a manner similar to the signal from receiving element Ar The signal from receiving element B is amplified in amplifier 15, converted to pulses in pulse generator 16, and widened-in pulse Widener 17 to fthe same width asV the output' gpulses from pulsev generator 7. Likewise the sig-V nal fronrreceiving element C is ampliiied in amp-liner 25, converted to a pulse train in pulse generator 26, land widened to the selected valuein pulse Widener 27. Control 250 which may'for' example vary the grid circuit time constant, allows variation"-` inthe width of the output pulses from pulse wideners 75, I7, and 27, for reasons Which'will appear hereinafter.

TheT outputs of-,p'ulse wideners 7,- 17, and 27, areYV fed tov ganged'variable delay devices 8,- 81,- and 82, respec` Y tors-maybtefused, a'prefer'red form of variable'delay device-for' accomplishing -this purpose is a cathode ray tube typeof signal storage-and play-back device, wherein signals tobe` delayed are recorded on theface of a cathode ray oscilloscope by a'irioving electron beam,` and played back-from the face of the oscilloscope by another'movingV electron bearri tracesA fthe path`of the recording beam at? a, time later than-the recording beam by an amount equal to the desired delay. Devices of this type are well known to the prior art, one such device being fully illustrated and its mode of operation fully disclosed in the patent to Riesz and Wertz 2,245,364. Because of the full disclosure of vall details of such a signal delay device in that patent, only 'a simplified disclosure of the essential elements of such a delay device will be given in the present application.

Referring to Figure 2, a device of the type shown in signal delay required by the present invention, is shown at 40, and includes two cathode ray tubes 41 and 42 disposed in face to face relationship and separated by a dielectric plate 42A. Cathode ray tube 41 constitutes a signal recording device and cathode ray tube 42 constitutes a signal playback device. Tube 41 includes cathode 43, electron beam intensity control grid 45, vertical deection plates 47 and 48, and horizontal deflection plates 49 and 50. Vertical deflection plate 47 of cathode ray tube 41 is connected to a sine Wave source designated as sweep oscillator 53. Horizontal deflection plate 49 is also connected through a conventional 90 phase shifter 44, to oscillator 53. This provides a circular sweep of the electron beam of tube 41 at the frequency of the sine wave output of oscillator 53. The frequency of'oscillator 53 is significant, and will be explained more fully hereinafter. As indicated in Figure 2 by the lead from oscillator 53 to theother delay devices, it is desirable to either synchronize the sweep oscillators of the three delay devices 8, 81, and 82 or to use a common sweep oscillator for the three delay devices to insure equal sweep frequencies for each.

Input signals to be delayed, such as for example the signal pulses from pulse Widener 7, are applied to the intensity control grid 45 of the recording tube 41. Such signals arerecorded on the face of the tube 41 along the circular path described by the electron beam. Since the rotating beam successively erases preceding signals as it records fresh signals, the maximum length of signal time which can be recorded on the face of tube 41 is equal to the time required for one revolution of the electron beam,'which is equal to the period of one cycle of the output of oscillator 53. Cathode ray tube 42 is provided with cathode 131, vertical deflection plates 132 and 133, horizontal deflection plates 134 and 135, and electron collector anode 136. The vertical and horizontal deflection plates of tube 42 are also connected in quadrature phase relationship by means of 90 phase shifter 137, and supplied with the sine wave output of oscillator 53 through fixed phase shifter 61 and variable phase shifter 62.

The electron beam of cathode ray tube 42 is therefore made to rotate in a circular path coincident with the path of the electron beam of tube 41. However, this rotating playback beam of tube 42 is delayed relative to the recording electron beam of tube 41 by the amount of phase shift imposed by phase shifter 61 and 62. When the delayed beam of tube 42 scans a signal recorded by tube 41, an output signal isl produced by secondary emission to collector anode 136 of tube 42.

`Phase shifter element 61 is preferably of such value as to provide a fixed phase shift of the sine wave output ofphase scan oscillator 53. Phase shifter 62 may be of any conventional type capable of providing a smooth continuous phase shift from zero to approximately 180, variable in aliner fashion. The exemplary phase shifter shown in Figure 2 for this purpose is a conventional goniometer type of phase shifter, consisting of two fixed coils 141 and 142 oriented in quadrature, and one movable coil 143 mounted for rotation through the fields of the fixed coils. In such a goniometer type of phase shifter the input signal is connected across the fixed coils, and the rotating coil is' mechanically rotated, as by shaft 83, within the field ofthe fixed coils, to provide an output signal from the rotating coil whose phase is delayed smoothly relative to the phase of the input signal by an Y Patent 2,245,364, suitable for accomplishing the variable 4 amount which varies linearly in proportion of the degree of rotation of the fixed coil.

Returning to Figure l, for each delay device there is a mechanical drive shaft equivalent to the shaft 83 shown' in Figure 2 for driving the rotating coil 143 of phase shifter 62. These mechanical drive shafts to delay devices 8, 81 and 82, are represented by broken lines 160, 161Hand 162. Drive shaft 160 is connected to driving motor 68 through rack and pinion 65, scotch yoke 66, and eccentric64. Similarly, drive shafts .161 and 162 are separately connected to motor 68 through similar racks and pinions 164, 165, scotch yokes 166, 167, and eccentrics 168, 169, respectively. ` Eccentrics 64, 168 and 169 are spaced 120; forA reasons which will appear hereinafter.

By-analogy to the mannerinwhich the playback beam of tube 42 is delayed behind the record beam of tube 41 in accordance with the angular position of phase shifter rotor'143 and sh'aft I83, it will be apparent that the amounts by which the respective signals from pulse wideners 7, 17, and 27 are delayed vary in accordance with the langular positions of respective shafts 160, 161 and In order to recover selectively only those signals Whose direction of arrival at the three receiving elements coincides with the selected reception bearing, it is necessary to eliminate all signals which do not emerge simultaneou-sly from the three variable delay devices 8, 81 and 82. This elimination of extraneous signals is accomplished in a coincidence gate 110, to which the outputs of delay devices 8, 81 and 82 are connected.

Reference is now made to Figure 3 wherein a preferred form of coincidence gate is shown schematically. Coincidence-gate -110 is of the signal amplitude selective type. It includes two pairs of triodes 111, 113, and 115, 119, each .pair having their cathodes tied together and plates tied together. The output of delay device 8 is connected to grid 116 of triode 111, the output of delay device 81 is connected to grid 117 of triode 113, the output of delay device 82 is connected to grid 113 of v triode 119. The output of each delay device is arranged to represent signals as positive pulses. The output from the parallel plates of triodes 111 and 113 is applied to the negatively biased grid 114Y of tube 115 through a phase inverting transformer 112. The output from the parallel plates of triodes 115 and 119 is applied through a secondphase inverting transformerl to the negatively biased grid of another triode 120.

In operation, the positive signals on grids 116 and 117 are combined and applied through transformer 112 as positive pulses to grid 114 of -tube 115. Only when said signals are overlapping do they reach grid 114 with sufficient amplitude to overcome its fixed negative bias. Similarly, signals reaching the plate of tube 11-5 combine with signals from delay device 82 and are applied as positive pulses to the grid of tube 120. Again only when these signals overlap do they overcome the fixed negative bias on tube `120. Thus the output tube of coincidence circuit 110 is restricted to signals coinciding in time at the outputs of each of the delay devices 8, 81, and 82. Or in other words, since the only signals passed by coincidence gate circuit 110 are those which arrive at grids 116, 117 and 118 simultaneously, an output signal from gate 110 indicates the arrival of signals at elements A, B and C so spaced in time as to be brought into coincidence by delay devices 8, 81 and 82, and hence having a direction of arrival corresponding to the instantaneous selected reception bearing. It will be apparent thatthe'precision with which pulses from the outputs of delay devices 8, -81 and 82 must be related in time, in order to provide simultaneous signals at the grids 116, 117 and 118 of coincident gate circuit 110, is dependent upon the width of these pulses. Very wide output pulses from delay devices 8, 81 and 82 need only be approximately coincident in order to overlap sufficiently to produce an output pulse from gate 1 10, whereas .narrower pulses from delay devices'8, 81 Aand 82 must bemore exactly related in time, or they will not overlap, jand 'will not produce'any output pulse from gate 110. Thus if the output pulses from pulse wideners 7, 17 and `27 are suiiciently wide, those pulses generated from signals received from a direction slightly diierent than the selected reception bearing which arrive at variable delay devices 8, 81 and 82 with a timerelationship slightly different than thatpassoci'ated with Vthe selectedreception bearing, will pass throghgate 110. l'

For this reason it maybe seen that the control 25,0, which varies the width of the output pulses from pulse4 wideners 7, 17 and 27, effectively/'varies the width of the directional zone about the selected reception bearing from which 'signals received `can still produce output pulses from gate 1710.

An explanation of the quantitative values of time by which signalsreceived by the three respectivev receiving elements-should be delayed, as a function of the direction of signal arrival" or reception bearing selected, will now be given. Figure 4 is a graph of the amounts of time by whichsignals from'icach of the three receiving elements must be delayed, plottedagainst the particular direction from vwhich lit is desiredV to receive signals selectively, assuming the sides ofthe equilateral triangle formed by the three receiving elements to beV of: such a length that the signal would require 100 microseconds to travel` this distance. As will be apparent from the: graph, signals received'from a bearing of0.",` i.e., signals traveling in the direction from element A to 0, reach element A 57.8 microseconds before arrival at 0.

A signal received from abearing of 90 arrives simultaneously at A and 0, and-when the selected receptionY bearing is 180, i.e., the direction from 0`to` A, signal arrival at element A `lags arrival at lby 57.8 microseconds; Signal arrival at element B likewise varies from 57.8 microseconds before arrival at. 0 when the bearing is 120, to 57.8,after arrival at 0 when the bearing. isV

300. Arrivalat C precedes' arrival at 0 by 57.8 microseconds for bearing 240 and lags arrival at 0 bythe same amount for bearing 60. Thus the amount ofV delay required toV compensate `for these differences in arrival times Varies,I through 360 of azimuth, from +57.8 microseconds to -57.8 microseconds; a total of 1.15.6 microseconds.` Since the signals cannot-,be delayed by a negative amount, the Variable delay devices 8, 81 and 82 are arranged todelay their respective signals through a range of from 0 tor 115.6 microseconds.

The goniometer phase Shifters' associatedwith Variable delay devices 8, 81` and 82,y such as phase shifter 62 of Figure 2, are therefore so designed, in relation to the output. frequency of their associated oscillators,y such as oscillator 53, that their maximum Vphase shift equals a time delay of 115.6 microseconds. If phase shifter 62, for example, provides phase shifts of from 0 to 180, then the frequency of oscillator 53 should be selected so that the period of one-half cycle is.. 115.6 microseconds. This would require an output frequency of The time between arrival` of. a signal at any of the receiving elements A, B, or C,.and arrival at 0, variesv and 82' mustfal'so var y sinusoidally. For this reasonV scotch yokes 66, 1'66 and 167i are employed to convert' the constant velocityV rotation ofthe'shaft' 'of motor 68j which are 120 to sinusoidally varyingangular displacement of shafts 160, 1 61, and 162.` Y .l

As is also apparent from Figure 4, the amount of delay to be imposed upon receivedsig'nals reaches a maximum or minimum for the three elements at respective bearings apart. iThis requires 1120" phase separation of the displacement-,of ` shafts 160, 161 and 162, which is provided by the arrangement of eccentrics 64, 168 and 169 in 120 spaced relation. e

Thus, in operation, rotation'of the shaft of motor 68 varies the delay imposed by phase Shifters -8, 81 and 82, in a siusoidal manner, and in 120 phase relation with each other. This varies through k360 of azimuth the selected receptionbearingfrom which direction signals arriving Vat elements A, B, and C are properly delayed to emerge simultaneouslyl from the outputs of variable delay devices 8,' 81 and 82.

The pulses which are united Vin coincidence gate 110 have the frequency of the pulses originally produced by pulse generators 6, 16 and 26, whichV as explained heretofore is theV same asthe frequency-of the wave signal intercepted by yreceiving eIementsA, B, and C.

To make the receiving system thusY far described frequency selective, a pulse periodicity selective circuit r150 may be provided.V This circuit, asshown in Figure l, is fed by the output pulses from coincidence gate after theyhave been shaped and invertedv by amplifier 149, and serves to discriminate against all pulses in they output of gate 110 which do noty have a periodicity corresponding to a. desired Vreceived signal. frequency. A

v The periodicity selective circuit. is shown, in greater detail in Figure 5. `Successive pulses from the output ofv coincidence gate 11'0 are shaped and. inverted by amplifier 149 and simultaneously yfed 4to, grid of twintriode 201, grid 211 of another twiny triode 208 andv are fed to grid 203 of triode 201 through a variable delay line 202. The plates and cathodes of twin. triodes 201and- 208 are tied together. Delay line 202 serves to establish the pulse spacing necessaryfto provide simultaneous arrival of pulses at grids 200 and 203, which of course produces a larger output pulse inthe plate circuitV 204 of the twin triode than results from ai pulse at only one grid.

Output pulses from the plate circuit of twin triode 201 are connected through another variable delay line 206, ganged with delay line 202, to always present equal delay, to grid' 207 of another-twin triode 208. Pulses from the plate' circuit of tube 201` are. applied through` a phase inverting transformer 204 sincethey are. desired inVA positive polarity at grid 207. Grid207 is so biased by battery 209 that only the largerampli'tude pulses produced by simultaneous; pulses at the grids 200 and 203 of twin triode 201 can cause conduction in the. right half of tube 208. As stated above, the other grid 211 of `twin triode 208 is connected directly byV conductor 212 to the` pulses from coincidence gate 110. Output pulses from plate circuit 214 of twin triode 208 are fed through a phase inverting transformer 214, to the grid 216 of an amplifier tube 215. The grid 216 of amplifier 215 is negatively biased to pass only the larger amplitude pulses produced in plate circuit of tube 208 bythe simultaneous arrival of pulses at grids 211 and 207.

Thus a pulse appears at the output of' amplifier 215 only when there arrives at thev input' of the periodicity selector circuit 150 the third ofthree` pulses spacedin accordance with the delay imposed by delay lines 202 and 206. Arrival of a fourth and iifth pulse, properly spaced, at the input of circuit 150 produces inturnA a` second and third output pulse from amplifier 215.v But any break in. the trainv of properly spaced pulses from gate 110 stops the output of pulses from amplifier 21SV until three morerproperly spacedV pulses are supplied to circuit 150. Y

Thus periodicity'selector circuit 150 operates to reject alll pulses which do not liaveltheperiodicity determined.

by delay lines202'and 206, and which do not arrive in trains of at least three. Of course additional twin triode stages identical to the two here shown may be employed, which would increase the number of input pulses in a trainnecessary to initiate an output from amplifier 215. Variation of the size of delay lines 202 and 206 varies the periodicity of acceptable pulses from coincident gate 10, and thus eifectively tunes the frequency of response of the receiving system. It will be understood other delay devices, such as delay multivibrators, may be substituted for delay lines 202 and 206.

Referring again to Figure l, from the output of pulse periodicity selector 150, pulses are fed to any suitable received signal indicating means 220. To correlate azimuth information with signal reception, the shaft of motor 68 is also coupled to indicator 220 to introduce information of the selected bearing and rate of sweep. Although many indicating devices may be made suitable, a preferable arrangement is to intensity modulate a cathode ray tube with the selected signal pulses and sweep said cathode ray tube with a circular sweep rotating simultaneously with motor 68. 4

For specific signal searching problems such as sector scanning, it may be desirable to stop, reverse, or control the speed of scanning. For this purpose a motor speed and direction control means 22]; is incorporated with motor 68.

It will be understood that the principles of this bearing sensing system are equally adaptable to selecting the bearing of signals reflected from intentionally illuminated objects. g

Although certain specific embodiments of this invention have been herein disclosed and described it is to be` understoodthat they are merely illustrative of this invention and modications may of course be made without departing from the spirit and scope of the invention as defined in the appended claims.

The invention `described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

1. A directional wave signal receiving system comprising three equilateral triangularly disposed omnidirectional receiving elements, three respective delay means for delaying the signals received by each of said receiving elements, control means for varying the delays of said three delay means in 120 phase relation for varying the time relationship of signals received by said three elements in accordance with a selected reception bearing to superimpose signals received by said three elements from said selected reception bearing, and means for displaying superimposed signals.

2. A wave signal receiving system having a selected directional Vreception zone rotating through 360 of azimuth comprising three omnidirectional receiving elements disposed in equilateral triangular relation; three respective delay means for delaying the signals received by each of said receiving elements, control means for varying the delays of said three delay means at a sinusoidal rate and in 120 phase relation, coincidence gate means for recovering simultaneous signals in the outputs of said respective delay means, and means for displaying signals recovered by said coincidence gate means.

3. In a wave signal receiving system for receiving signals from a selected direction, three omnidirectional receiving elements disposed in equilateral triangular relation, respective' pulse generator means fed by the output of said respective receiving elements for generating pulse trains having -the same periodicity as'the received wave signals, respective delay means for varying the phase relation of said respective pulse trains in accordance with the relationship of the times of arrival at said receiving elements of a signal fromsaid selected direction, whereby pulses generated from signals received from said selected direction are superimposed, and means for indis eating said superimposed pulses.

4. A directional-wave signal receiving system having a variable selected reception direction comprising three receiving elements disposed in equilateral triangular relation, whereby the relationship of the times of arrival of a received signal at said three receiving elements denotes the direction of arrival of said signal relative to the orientation of said receiving elements, signal delaying means remote from said receiving elements for relatively delaying signals received by said three elements in accordance with the arrival time relationship denoting said selected direction, whereby signals arriving yat said receiving elements from said selected direction are superimposed, means for communicating signals received -by said three receiving elements to said signal delaying means, and means for indicating superimposed signals.' 5. In a wave signal receiving system having three omnidirectional receiving elements disposed Vin equilat; eral triangular relation, means for recovering only signals received from a selected direction comprising pulse generator means for deriving from a received wave signal respective pulses having a time relation equal to the relation of the respective times of arrival of said received wave signal at said three receiving elements, means for delaying said respective pulses by respective amounts of time differing as the times of arrival at said receiving elements of a signal from said selected direction, whereby pulses derived from a signal received from said selected direction are brought into coincidence, and means for indicating coincident pulses.

6. A wave signal receiving system for receiving sig-v nals from a selected direction comprising three omnidirectional receiving elements disposed in equilateral triangular relation, signal delay means for each receiving element for delaying signals received by each receiving element an amount equal to the time for signals from said selected direction to travel between the nearest receiving element to said direction and the respective re-` ceiving element of each delay means, means communieating signals received by each of said elements to said respective delay means, coincidence gate means for superimposing simultaneous input signals, means for connecting delayed signals to said coincidence gate means,

and means for indicating superimposed signals.

7. A wave signal receiving and indicating system for receiving signals from a selected direction comprising three omnidirectional receiving elements disposed in equilateral triangular relation, signal delay means for each receiving element for delaying signals received by each receiving element, means communicating signals received by each of said receiving elements to said respective delay means, coincidence gate means for superimposing simultaneous input signals, means for connecting delayed signals to said coincidence gate means, control means for varying the delays of said several delay means sinusoidally in phased relation from zero to a maximum amount proportional to the spacing of said receiving elements, whereby said selected direction is varied through 360, periodicity selective means fed by the output of said coincidence gate means for rejecting all of said superimposed signals except those having a selected periodicity, and means for indicating output signals from said periodicity selective means.

8. In a wave signal receiving system for receiving signals from a selected direction, three omnidirectional receiving elements disposed in equilateral triangular relation, respective pulse generator means fed by the output of said respective receiving elements for generating pulse trains having the same periodicity as the received wave signals, respective delay means for varying the phase relation of said respective pulse trains, control means for varying the delays of said respective delay means sinusoidally inv120 phase relation from zero tol 9 a maximum amount proportional to the spacing of said receiving elements, coincident gate means fed by said delayed pulse trains for producing an output signal responsive only to the simultaneous input of a pulse from each delayed train, and means for indicating said output signa s.

9. A wave signal receiving and indicating system for receiving signals from a selected direction comprising three omnidirectional receiving elements disposed in equilateral triangular relation, signal delay lmeans for each receiving element for delaying signals received by said receiving element, means communicating signals received by each of said receiving elements to said respective delay means, coincidence gate means for superimposing si- Y multaneous input signals, means for-connecting delayed signals to said coincidence gate-means, control means for varying the delays of said several delay means sinusoidally in 120 phased relation from zero to a maximum amount proportional to the spacing of said receiving elements, whereby said selected directionV is varied through 360, and means for indicating signals superimposed by said coincidence gate means.

10. A directional Wave signal receiving system comprising three omnidirectional signal receiving elements disposed in equilateral triangular spaced relationship, signal delay means for each of said receiving elements, communication link means for conveying the signals int, gtereepted by said respectivereceiving elements to said respective delay means, coincidence gate means for'prol ducing an output signal responsive only to ak plurality means, periodicity selector meansffor rejecting kall sigrespective delay means in a sinusoidal manner from zero 10 to a maximum amount proportional to the spacing of said receiving elements, and means for operating said respective control means in phased relationship to superimpose signals received by -said receiving elements from any one direction, whereby said one direction is varied through 360 of azimuth. v

1l. In a wave signal receiving system having three omnidirectional receiving elements disposed in equilateral triangular relation, means for recovering only signals received from a selected directional zone comprising pulse generator means for deriving from a received `wave signal respective pulses having a time relation equal to the relation of the respective times of arrival of said 151 received wave signal at said three receiving elements,

means for delaying said respective generated pulses by respective amounts of time differing as the times of arrival at said receiving elements of a signal from the center bearing of said selected directional zone, whereby delayed pulses derived from a signal received from said center bearing are brought into exact coincidence and those from other directions within said selected zone are approximately coincident, coincidence gate means fed by said delayed pulses for generating an output pulse responsive to the coincidence of a portion of said delayed pulses, means for varying the duration of said generated pulses, whereby delayed pulses derived from signals received from said selected directional zone coincide during a portion of ftheirduration, and meansvforindicating-saidY output pulses. 'Y

l References Cited in the le of this patent UNITED STATES PATENTS

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