US2597862A - Electronic lobing - Google Patents

Description

y 7 1 J. H. GREIG 2,597,862

ELECTRONIC LOBI'NG Filed May 3, 1948 I 3 Sheets-Sheet 1 ANTENNA DIRECTIONAL E r LOBER ANTENNA 3 |9 l |2 V GATED H.F T-R Box WATT. M 1 GATE I l l E I 5 MODULATOR 5 AND T; 5 RANGE UNIT 3 5 SWEEP BEARING ---3 CIRCUIT -ELEVATION SEPARATION DOWN CIRCUITS "78 E 151E X/Q LEFT RIGHT |7A ILELE JOHN H. GREIG May 27, 1952 J. H. GREIG ELECTRONIC LOBING Filed May 3, 1948 5 Sheets-Sheet 2 76 F LOBE OF ANTENNAS l7A AND I 31 32 3o 7 s k glwuem bcvv JOHN H. GREIG May 27, 1952 J. H. GRElG 2,597,862

ELECTRONIC LOBING Filed May s, 1948 s Sheets-Sheet 3 I15; .LD

INPUT TO SPARKGAP 25 m I w 5 INPUT TO SPARKGAP 26 2 IE 5 c: NPUT TO SPARKGAP 27 III a '5 INPUT TO SPARKGAP 28 11 TIME JOHN GREIG imp Patented May 27, 1952 lTED STATES PATENT FFECE (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) This invention relates to radio-echo objectlocating and ranging systems and, more particularly, to: an electronic arrangement for electrically lobe-switching an antenna system for selectively feeding the received signals of a plurality of receiving antennas in a system of the above class to a single receiver for signal comparison purposes on successive pulses and/or for antenna orientation with respect to the target. 7

In radio-echo object-locating and ranging systems of the kind adapted to alternately produce two differently directed antenna fields or lobular directivity patterns in both the horizontal and vertical planes for search and heightfinding purposes, antenna systems are employed in which a transmitting, antenna, is intermittently fed from a high frequency transmitter while receiving antennas are made receptive to passage of reflected signals in a manner to render them sequentially effective and ineffective. The lobe switching of these receiving antennas has heretofore been accomplished through the use of mechanical or electromechanical switching arrangements which devices function very slowly as compared with the pulse repetition rate or rates employed. Furthermore, the mechanical switching devices also switch the lobes successively through four quadrants besides introducing complications which increase the cost and. maintenance of the antenna system.

, According to the present invention lobe switching is accomplished in a radio locating system of the above kind solelyby purely electrical or electronic means. In accordance with the invention the antennaarraycomprises a center transmitting antenna or radiator which is intermittently excited from a high frequency generator, and a plurality of receiving antennas positioned near the center radiator to give overlapping receiving lobes. Spark gap or gas tubes are provided in the feeds of the receiving antennas and these tubes, are fired in the manner of the invention so asto be rendered effective and ineffective in a predetermined recurring order during the receiving condition, such as,

for example, in the "sequential directions of downward and upward, left and right, or vice versa to pass the received echo signals to a single high-frequency translating apparatus as directional characteristics for signal comparison in magnitude and/or to hearing and elevation separation circuits, any error signals, obtained from such separation circuits beingused to drive the antenna in a direction to point it at the target, or "for meter indicationsr I j The present invention features an antenna array in which the transmitting and the receiving antennas are all of wave guide construction and disposed within a parabolic reflector at the focal region thereof in order to obtain directional radiation and reception patterns, respectively. The receiving antennas are placed vertically and horizontally at each side of the center transmitting antenna and all have their longitudinal axes arranged in the same direction. The center transmitting antenna is periodically excited and during its non-radiating period the receiving antennas are alternately rendered conducting and non-conducting to passage of received waves of the radiated frequency to a common radio receiver and to the bearing and elevation separation circuits. Electronic means are provided by this invention for rapidly producing this sequential transmission of the received waves by the receiving antennas to the receiver and the separation circuits during the non-transmitting period of the transmitting antenna. Means comprising variable non-sinusoidal voltages in phase-quadrature and synchronized to the extinction period of the radiated pulse so that each of said voltage variations has a duration approximately equivalent to the interval between successive radiated pulses, are applied successively to spark gaps associated with resonant cavities coupled to the receiving antennas whereby the receiving antennas pass the received energy to the receiver and to the bearing and elevation separation circuits during the non-radiating period.

One object of this invention, therefore, is to provide in a directional antenna system arranged for two-position reception in both the horizontal and the vertical planes, electronic means for rendering the two receiving channels in each plane alternately effective and ineffective to passage of the received signals to the receiving and separating equipment.

Another object of'the invention is to provide an improved antenna arrangement whereby the directive signals as received are switched solely by electronic means to a receiver and separation circuits to produce successive electrical indications for denoting the downward, upward, left and right deviations of a reflecting body in space with respect to the axis of the radiated beam from the transmitting antenna of the system, and wherein zero-voltage signals in azimuth and in elevation shall be obtained when the antenna array is pointed directly at the reflecting body in space.

I A further object of the invention is to provide high speed lobing for the purpose of reducing the effect of signal fading to a minimum.

Other objects, features and advantages will be apparent from the following description of the invention, pointed out in particularity by the appended claims, and taken in connection with the accompanying drawings in which:

Fig. l is a block diagram of a system embodying the invention;

Fig. 2 is a front view of an antenna system in accordance with the invention but with the parabolic reflector normally associated therewith removed;

Fig. 3 is a vertical sectional view of the antenna array of the form shown in Fig. 2, taken substantially on the line 3--3 of Fig. 2;

Fig. 4 is a horizontal sectional view of the antenna array of the form shown in Fig. 2, taken substantially on the line 4-4 of Fig. 2;

Fig. 5 shows the gated video voltage Waveforms going between the receiver and the bearing and elevation separation circuits of the Fig. 1 radio location system;

Fig. '6 illustrates the double-lobe characteris tic pattern of either pair of receiving antennas HA and "B or I70 and I'ID of the array such as shown in 'Fig. 2, taken substantially on lines 33 or 1- 3 respectively thereof;

Fig. "7 is a schematic diagrammatic view of a longitudinal section of one of the receiving waveguide antennas showing the novel sparkgap switching "arrangement in accordance with the invention; and

Figs. 8, '9 and 10 are curves explaining the operation of this invention.

Referring 'to Fig. -1 there is shown the high speed lobin'g system of the .present invention applied to a known form of automatic radio-echo object-locating "system comprising a directional antenna generally designated III to which energy is supplied from a high frequency radio transmitter I I. The directional antenna ID has the geometrical arrangement shown in Figs. 2, 3 and 4 which comprises a parabolic reflector I5 and an array in the focal region thereof comprising a center or transmitting wave-guide type antenna I6 with four adjacent receiving waveguide type antennas I 1A, NB, NC and I'iD. The center antenna I6 of the array I0 is supplied with high frequency pulse energy from transmitter II connected to keyer 'IQ which in turn is connected to a modulator and range unit 20. Of the apparatus shown by block in Fig. 1, antenna I0 is shown in greater detail in Figs. 2, 3 and 4. The other blocks arenot shown in detail but all represent circuits well known in the prior art. No specific circuit arrangement of these units is claimed as apart of my invention. An example ofprior art devices suitable for use with this invention may be found in the Patent 2,407,898 to Norgaard filed June 8, 1942. Referring to Norgaards Fig. '1, his transmitter 1 may be substituted for my H. F. transmitter II. However, since 'I have a separate transmitting antenna, I6 in Fig. 2, my transmitter is connected directly to the antenna and not through the T-R equipment 2 as shown by Norgaard. Norgaards transmitter synchronizing generator 16 may be substituted for my keyer I9 and his square pulse generator and aperture pulse generator 45 may be substituted for my modulator and range unit 20. His square pulse generator 15 is suitable for producing the square wave which I have shown in 'Fig. 8. 'Norgaards generator 15 operrates to key his transmitter in the same manner in which my modulator and range unit keys my transmitter II. It likewise operates to synchronize his aperture pulse generator which provides a variably delayed gate for his receiver 4 for selecting echos from a particular target in the same manner that my range unit supplies a gate for my receiver I8. His receiver 4 is a suitable equivalent for my receiver I8. However my receiver additionally supplies an ungated output for viewing on indicator 2 I. Likewise Norgaards T-R equipment 2, with the transmitter connection eliminated, is equivalent to my T-R box I2. The R.-F. energy thus supplied to the center antenna IE will produce a beam pattern such as shown at I9 in Fig. 6. Receiving antennas IIA, I73, I10 and IID are symmetrically disposed about and in proximity to the center transmitting antenna I6 and they are rendered successively conductive and non-conductive in a predetermined recurring order whereby they are directed to cover the field of view so as to receive and pass in succession the reflected echo signals from downward, upward, left and right directions, the directivity of the respective lobe patterns of these receiving antennas being rapidly switched electronically in the above sequence between the four positions of coverage whereby the four echo 'pips will pass through lober l3, T-R boX I2 and receiver I8 to the bearing and elevation circuits '22 where the amplitude of the left lobe and the right lobe are compared, and similar upward and downward lobes are compared, to produce error signals to drive the antenna 'control 23. The antenna lober I3 contains spark gaps 25, 26, 21 and 28, shownin Figs. 3 and 4 and further described below, and supplies pulses of voltage successively to each to render them sequentially conducting. The pulses supplied to each are shown in Fig. '10 and are produced by known methods from the square wave shown in Fig. 8. An example of a suitable circuit for producing these pulses is disclosed in U. S. Patent 2,306,386 issued December 29, ran 'to John Hollywood. fiollywoods'circuit is further described in U. S. Patent 2,406,760 'file'd Sept/1 7, 1940 by Goldmark. Hollywood's circuit shown in Goldmarks Fig.5 as "a triple gate generator may be used in my antenna lober f3 to;sequential-ly fire the spark gaps. Since I'have-four channels one extra multiv'ibrator should be added for-example between plate 'P' an'dire's'istor '58 of Goldmark, thereby producing four sequential outputs at 52 instead of the "three illustrated in "Goldmarks Fig. '1. 'Thesq'uarewave from my Fig. 8 would preferably be applied as negative 'di'iferentiated pulses to trigger pulse input line "51 of Goldmarks Fig. 5. 7

Where my invention is used with an automatic follow up system, asillustrated in Fig. '1, the "receiver signals from each pair of antennas are compared in amplitude in the circuit 22 which.

produces a control signal for the antenna con,- trol 2'3. example of known devices for "accomplishing this result is found in U. Patent 2,422,334 Beclfol'd filed January 23, I943. Bedfords signal separation circuits consisting of switches 42 4B, 47, 48., '63, 6B, '67.may .be substituted for my circuit 22 andlhis control amplifiers 61 and 62, and motors "71 and '12 may be substituted for my antenna-control .23., With my invention the mechanical switching of Bedford is preferably replaced with electronic switching such as that disclosed by Hollywood, above.

According to one feature of the invention this rapid electronic beam lobing i's'effected bymeaus of the spark- gap devices 25, 26, 21 and 28 respectively'which are fired in turn in the manner hereinafter to be described to render the waveguides llA, NB, NC and ND successively conducting to passage of the reflected radio frequency energy. The four receiving antennas are intermittently connected through their respective spark gap devices Within the antenna lober unit l3 through the T-R box l2 to the radio receiver l8. Thus, four echo pips appear in succession on the gated-video lead from the receiver I3 to the bearing and elevation separation circuits 22 and each pip in the order corresponding to the side to which the detected object lies relative to the radiated-beam from the center antenna I5. I

In Fig. 5 there is shown a representative type of gated video voltage signals supplying information from the receiver: l8 to the bearing and elevation separation circuits 22 which control the antenna control 23 for moving the antenna Ill. The order given these voltage signals or pips indicates the direction in which the detected object lies while the respective amplitudes of these pips indicate theclirection in which antenna is off-center with respect to the target. When the antenna I0 is directly pointed at the target in elevation the amplitude of the upward and downward echo pips U and D respectively will be of equal height, and in train the left and right echo pips L and R. respectively will be of the same size.

In Fig. '7 there is shown a simplified schematic diagram of one of the receiving antennas including the switch tube- 25 which is mounted in a resonant cavity to form the electronic antenna lobe switch, the arrangement being identical for [TD so that this description will sufiice for all.

The switch tube 25 comprises a glass envelope 30 within which is mounted in juxtaposed relationship a pair of conical-shaped metal electrodes 3i and 32 which act as a spark-gap when fired by the auxiliary electrode 33, as will be hereinafter described. The distal ends of the electrodes 3| and 32 are brought out through the glass envelope 30 and connected to the mounting stub 35 to form a resonant cavity. The distance from the line of centersof the spark gap electrodes 3| and 32 topoint of attachment of the stub 35 to the receiving waveguide antenna HA is electrically a half-wavelength.

Referring further to Fig. 7 the operation of the spark gap devices 25, 26,21 and 28 is identical so that the description of. one will suflice for the others and is as follows: When the spark gap 25 is non-conducting the receiving waveguide antenna HA is closed due to the properties of the tuned cavity whereby the high impedance at the spark gap at a distance A/ 2 therefrom is reflected so as to appear as an open circuit thereby rendering the receiving waveguide antenna l'lA non-v conducting. Each spark gap has an auxiliary electrode 33 and by the application thereto of an applied voltage such as, for example, squarewave I of Fig. in the case of the spark gap 25, the latter is ionized and becomes conducting, and the associated wave-guide antenna HA is opened due to the properties of the shorted stub. In other words, when the spark gap 25 is fired by the applied square-wave I of Fig. 10 a low impedance path is produced which is reflected at a distance M2 as a shorted line thereby enabling the wave-guide antenna [1A to pass received signals or back-directed energy to the receiver and indicator. The variable voltages shown in curves I, II, III and IV of Fig. 10 are applied of received waves to the translating and indicating equipment is effected in succession in the wave-guide antennas IA, [1B, [1C and ND respectively. Rapid deionization takes place in the spark gaps when the square-wave firing voltage is removed. i

The synchronized square-wave voltages which are applied in phase-quadrature to the electrode 33 of the spark gap devices 25, 26, 21 and 28 are indicated in the curves 1, II, III and IV respectively of Fig. 10, as derived .from the output of suitable mixers (not shown) whose input comprises the synchronized impulses indicated in curves I and II of Fig. 9 from two frequency dividers (not shown) which, in turn, are derived from the square-wave pulses indicated in Fig. 8 of a suitable multivibrator.

Important advantages of the invention are (1) fast switching 'due to use of an electronic tube as the electrical switching arrangement With each stub in thewaveguide transmission line of each receiving antenna feeding the common translating equipment; (2) an antenna structure is obtained which is formed to be rid of any electric or mechanical disadvantages of the prior art mechanical or electromechanical lobe switching devices, and is adapted especially for use in connection with rotatable antenna structures; (3) permits varying the sequence of lobe-switching as desired,at any time, by simply changing the sequence of the firing signals to the spark gaps; (4) permits suchlobe-switching change-overs to be made while the apparatus is in operation.

While there has been described a preferred embodiment of the invention, as applied to a waveguide transmission line, it will be obvious to those skilled in the art that various changes and modifications may be made therein such as, for example, by use of coaxial conductor transmission lines, without departing from the spirit and scope of this invention as defined by 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. In a radio pulse echo system, high speed lobing apparatus comprising, a pulse transmitter, a radiating means connected to said transmitter for radiating the transmitter pulses, an echo receiver, a plurality of echo receiving means ar ranged in close proximity to said radiating means, receiving transmission line means connecting each of said echo receiving means to said receiver, a voltage source having an equal plurality of outputs of unlike phase and successively aradiating means connected to said transmitter for radiating the transmitter pulses, an echo receiver, a plurality of echo receiving .means arranged in close proximity to said .radiating means, receiving transmission line means connecting each of said echo receiving means to :said receiver, a voltage source having :an equal plurality of outputs of unlike phase and successively producing pulses at each of said :outputs. said voltage source producing an output pulse :for each transmitter pulse, an equal plurality of transmission line stubs each disposed in series connection with one of said receiving lines, a plurality of spark gaps each disposed within one of said stubs a half wavelength from the :associated receiving line, each of said spark gaps being connected to a different output of said voltage source to sequentially permit the transmission of echo pulses through said receiving lines.

3. In a radio pulse echo :system, .high speed lobing apparatus comprising, a pulse transmitter, a waveguide transmission channel connected to said transmitter for radiat ng the transmitter pulses, an echo receiver, aplurali'ty of waveguide 8 disposed within .one of. said stubs a half wavelength from the associated receiving channel, each of said spark gaps being connected to a different output of said voltage source to sequentially permit the transmission of echo pulses through said receiving channels.

JOHN H. GREIG.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,082,347 Leib June :1, 1937 2,083,242 Runge June 8, 1937 2,207,267 Plaistowe July 9 1940 2,210,666 Herzog Aug. 6, 1940 2,281,274 Dallenbach Apr. 28, 1942 2,407,250 Busignies Sept. 10, 1946 2, 08,250 Fiske Sept. 24, 1946 2,408,425 ,Jenks et al. Oct. .1, 1946 2,415,242 Hershberger Feb. 4, 1947 2,416,155 Chubb, Feb. 18, 1947 2,418,124 Kandoian, Apr. 1, 1947 2,425,328 Jenks et al. Aug. 12, 1947 2,480,829 Barrown'et al Sept. 6, 1949 2,506,617 Sackville May 9, 1950 FGREIGN PATENTS Number Country Date 555,052 Great Britain Aug, 3, 1943 678,290 Germany July 12, 1939 OTHER REFERENCES Practical Analysis of Ultra High Frequency, by Meagher and Markley, August 1943, page 17.

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