US2981948A - Simultaneous lobing array antenna system - Google Patents

Description

April 25, 1961 Filed May 29. 1956 L. A. KURTZ SIMULTANEOUS LOBING ARRAY ANTENNA SYSTEM 2 Sheets-Sheet 1 Louis A. Kurfz,

I/VVE/VTOR.

April 25, 1961 A. KURTZ 2,981,948

SIMULTANEOUS LOBING ARRAY ANTENNA SYSTEM Filed May 29. 1956 2 Sheets-Sheet 2 LOUIS A. Kunz,

"selective coupling units.

SIMULTANEOUS LOBING ARRAY ANTENNA SYSTEM Louis A. Kurtz, Los Augeles, Califl, assiguor to Hughes Aircraft Company, Culver City, Calif., a corporation of Delaware Filed May 29, 1956, Ser. No. 588,155 4 Claims. (Cl. 343-771) This invention relates to Simultaneous lobing antenna systems, and more particularly to the utilization of a plurality of array elements which are integrated'with one another to provide simultaneous lobing for amplitude or phase comparison monopulse angular tracking.

Heretofore simultaneous lobing antenna systems utilized in wave energy tracking systems made use of a plurality of individual antenna elements, each of which radiated and absorbed as a point source. The most widely used simultaneous lobing antenna of the prior art comprised in combination a large parabolic reflector, a single radiating antenna element positioned at the focal point of the reflector and several receiving antenna elements positionedin the focal plane of the reflector and displaced from the reflector axis. The reflector provided beam shaping for the several antenna elements.

For one-dimensional lobing, a conventional lobing antenna utilized a single radiating antenna element occupying the position at the focal point and a pair of receiving antenna elements symmetrically spaced about the radiating antenna element in the focal plane but displaced from the reflector axis. For two-dimensional .lobing two more receiving antenna elements are added to the hereabove described antenna. These four receiving antenna elements usually occupy the position of the corners of a square having the radiating antenna element at its center.

To derive signals from the receiving antenna elements which are proportional to the position of a target, the receiving antenna elements are interconnected by means of a plurality of sum-and-diflerence hybrid tees. The hybrid tees operate upon the wave energy and compute the vector sum and the vector difierence of the wave energy received by each of the receiving antenna elements. Output signals from the hybrid tees are utilized for angular tracking in a manner well known to those skilled in the art.

It is an object of this invention to provide a simultaneous lobing antenna system including radiating and receiving antenna elements arranged in arrays capable of shaping a beam without an antenna reflector.

It is a further object of this invention to provide a new and novel simultaneous lobing antenna array which incorporates phase selective coupling units as an integral part thereof.

It is a still further object of this invention to provide a simultaneous lobing antenna system for amplitude or phase comparison monopulse angular tracking which incorporates antenna array elements and hybrid type coupling units integrated to form a single compact unit.

'The simultaneous lobing antenna array system in accordance with this invention comprises a novel combination-of a single antenna array and one or more phase Essentially a two-dimensional array antenna which includes columns and rows of radiators is unidirectionally subdivided into one or more pairs "of array antenna elements. antenna array system of this invention, the subdivision Upon radiation, from the,

' atent 2,981,948 Patented Apr. 25,1961

is entirely ineifective and the 'full array is utilized for shaping the illuminating wave energy beam. Upon reception of the reflected portion of the illuminating beam by the antenna array system, the unidirectional subdivisions of the antenna array become fully efl ective and divide the antenna array into individual array antenna elements each separated electrically from the other. Each of these antenna array elements has its own characteristic wave energy pattern, usually identical to one another which is responsive to a wave energy signal the phase of which depends on the path distance between the sourceof the incident wave energy and the distance to the individual array element axes. If the source of the reflected wave. energy is at a great distance, the magnitude of the Wave energy received by each element is equal but differs in phase.- During reception, therefore, the. array elements perform very much like the individual element sources positioned within a parabolic reflector of theprior art. I

The unidirectional subdivision of the antenna array is produced by a combination of phase selective coupling units such as directional couplers or. hybrid junctions and the waveguides which comprise the antenna array. This combination provides the necessary vector ad'ditions and vector subtractions for deriving waveener g'y signals for simultaneous lobing techniques. The input signal to and the output "signal from the antenna array system of this invention is' comparable to that of the prior art simultaneous antenna system, and the antenna array system of this invention may therefore be used with conventional tracking systems. The invention will be more fully described by reference to the attached drawings which illustrate several embodiments of it in which:

Figs. 1-3 are perspective views of difierent embodiments of the one-dimensional simultaneous lobing antenna array system in accordance with this invention;

Fig. 4 is a schematic diagram illustrating the twodimensional simultaneous lobing antenna array system, and

Figs. 5-8 are perspective views of different embodiments of the two-dimensional simultaneous lobing al'r tenna array system in accordance with this invention.

Referring now to the drawings and more particularly to Fig. 1, there is showna one-dimensional simultaneous lobing antenna array system comprising in combination an antenna array 10 and a hybrid tee 12. The antenna array 10 is divided into two identical antenna array elements 16 and 18 by ametallic interface14. Each of the antenna array elements 16 and 18 are provided with a plurality of parallel. radiation slots v20 located alternately on each side of the longitudinal center line 22 of the antenna array 10 and separated from one another by approximately one-half of the working wavelength of the wave energy propagated bythe array 10. The hybrid tee 12 has a pair of symmetry arms 24 and 26, a sum arm 28 and a diiference arm 30. ,The symmetry arms 24 and 26' are coupled respectively to of:- posite sides of the antenna array 10 and therebypr'ovide Wave energynfeeds to the array elements 1 6 and 18.

Wave energy fed into the sum arm 28 is divided: by the hybrid tee 12- into two equal portionsi which are propagated by the pair of symmetry arms 24 and 126. Because of the orientation'of' the sum arm with respect to the difierence arm no energy will pass into the difference arm 30 as is well known to those skilled in the art. The Wave energy propagated by the symmetry arms 24 and 26'is received by the antenna- array elements 16 and 18 respectively from where it is radiated into space upon excitation of the radiation slots 20. The direction of the waveenergyso radiated' depends on the phase relation of the wave energy radiated by each of the radiation slots 20. The radiation slots 20 of Fig. 1 are spaced in such a way that the phase of the wave energy radiated by neighboring slots differs by one-half wavelength, The direction of radiation fromthe array system is therefore perpendicular to the plane of the antenna array 10.. .Radiation from antenna array element 16 defines an array element axis 17 and similarly 'radiation. from antenna array element 18 defines an array element axis 19. Radiation from the array elements combine to form a single radiated beam defining an array axis 11. r Wave energy received by the antenna array 10 may be regarded as received by the antenna array elements 16 and 18, respectively. The antenna array elements act as independent absorbers of wave energy, each element absorbing an amount of wave energy proportional to the angle between the incident wave energy and the array element axes 17 and 19. ,If the source of the incident "wave energy is located a great distance away, as is nor- 7 mally the case, the angle of incidence will be equal for all array elements. Therefore, the magnitude of the wave energy absorbed by each array is approximatelythe same but the phasesof the wave energy signals absorbed ;will differ by an amount equal to the path difference from the source of the incident wave energy to the in- ,dividual antenna array elements. Wave energy signals fromthe antenna array elements are propagated towards .respective symmetry arms. The interface 14 is positioned in such a way that wave energy received by the elements seesa short circuit. The hybrid tee 12, as is known to those skilled in the art, performs vector addiftions and subtractions of the wave energy signals received by symmetry arms 24 and 26 so thatthe sum arm 28 will provide an output signal proportional to the 'vector sum and the difference arm 30 will provide an output signal proportional to the vector difference of the wave energy signals developed by the antenna array elements 16 and 18. The output from the sum arm 28 provides an indication of the range of the wave .energy source and the output from the difference arm 30 provides an indication of the angle between the wave energy source and the array axis 11. i Fig. 2 is a modification of the simultaneous lobing antenna array system of Fig.1, wherein an antenna array 32 is divided by an interface 34 into two antenna array elements 36 and 38 which include radiation slots 40. .Ahybrid tee 42 having a pair of symmetry arms 44 1 and 46, a sum arm 48 and a diiference arm 50 is cou- Ipled to the antenna array 32 in such a manner that the symmetry arms 44 and 46 supply wave energy to the . jarray elements 36 and 38 at the midpoints of the latter.

Fig. 3 is further modification of the simultaneous lobing antenna array system of Fig. l wherein the path of symmetry arms 52 and 54 of the hybrid 56 respectively "provide the equivalent of the antenna array elements 16 and 18 of Fig. 1. The radiation slots 58 are set diagonally into the symmetry arms 52 and 54 to enable the exchange of wave energy between the array elements and free space. The hybrid tee 56 has a sum arm 60 and a difference arm 62. The operation of the antenna system of Fig. 2 and Fig. 3 is the same as has been described in conjunction with theantenna system 'of Fig. 1. j The schematic diagram shown in Fig. 4 illustrates the .principle of operation of a generalized two-dimensional simultaneous lobing antenna system. Four individual antennas such as element or arrays A, B, C and D whose respective radiation axes. are symmetric with respect to same center line are interconnected by four phase selective coupling devices H H H and H The purpose of the coupling devices and their particular method of interconnection are to provide three outputs, namely and -l where each letter represents the vector quantity of the wave energy signal developed by each of the antennas A, B, C and D. Essentially all coupling devices have two symmetry arms S, one sum arm designated, by a plus sign and a dilierence armdesignated by a minus sign. The symmetry arms of device H are joined to antennas A and B, respectively, so that its sumarm has an output equal to and its difference arm has an output equal to The symmetry arms of device H, are joined to antennas C and D so that its sum arm has an output (0+ D) and its difierence arm has an output The symmetry arms of device H are joined to the sum arms of devices H and H respectively, so that the sum arm of device H has an output (A+ 0+ D) and the difference arm of device H has an output I (A+B)(C'+ D) The symmetry arms of device H are joined to the difference arms of devices H and H respectively, so that the sum arm of device H has an output of (A C) (3-!- D) The difference arm of device H is not required for simultaneous lobing.

As mentioned above, each of the antenna elements A, B, C and D has a radiation axis. The four radiation axes define a systems. axis symmetrically located with respect to all four antenna element axes. Assuming a source of radiation or a reflector located in space in the proximity of but not on the systems axis, the energy-received by each of the antenna elements A, B, C, or D will be proportional in.magnitude to the angle between the source and the array axis, and the respective phases will differ by the difference in path length between the wave energy source and the individual array elements. Fig. 4 illustrates how the position of that source may be found by the methods referred to as two-dimensional simultaneous lobing. The sum arm of the coupling H gives the range of the source. The difference arm of coupling H provides an output which is proportional to the angle that the source made with the systems axis projected upon a plane containing the systems axis and midway between the antennas A and B. The sum arm of coupling H has an output which is proportional to the angle made by the source and the systems axis projected upon a plane containing the systems axis and midway between the antennasA and C. In other words, the difference arm of coupling H and the sum arm of coupling H give the position of the source in a-cartesian coordinate system.

Fig. 5 is a two-dimensional simultaneous lobing antenna array system in accordance with this" invention wherein a plurality of waveguides 70 are placed side by side defining a two-dimensionalarray 74-. One side of the array 74.is provided with columns and rows of radiation slots 72 for the. interchange of wave energy between the array and 813366.. Each of the waveguides 70 is divided by 75 means of an interface 76 into two equal portions. ,The

symmetry arms 78 and80 of a hybrid tee 82 are slot respectively to the sum arm 99 of hybrid tee 82 and the sum arm 100 of hybrid tee 90. Similarly, the symmetry arms 93 and 95 of hybrid tee 94 are coupled respectively to the difference arm 81 of hybrid tee 82 and the difierence arm 91 of hybrid tee 90. The sum arm 186 and the difference arm 108 of hybrid tee 96 and the difierence arm 110 of hybrid tee 94 provides the output terminals for this two-dimensional lobing antenna array system.

The operation of this system is best understood by considering the antenna array 74 divided into four equal array elements which are designated A, B, C and D respectively, in conformity with the illustrative diagram of Fig. 4. The division of the antenna array 74 into four antenna array elements A, B, C and D is caused by the interface 76 which splits the array into two halves and the hybrid tees'82 and 90 which further divide each of the halves. Wave energy fed into the system through the sum arm 106 is divided by the hybrid tee 96 into two equal wave energy portions which are conveyed via the symmetry arms 97 and 98 to the hybrid tees 82 and 90. The hybrid tees 8 2 and 9t divide the wave energy received into two equal wave energy portions so that one-quarter of the wave energy applied to the sum arm 106 is conveyed to the symmetry arms 78, 80, 86, 88 respectively. The coupling slots 84 and 92 couple this wave energy into the four antenna array elements A, B, C, and D from which this energy is radiated into space along the antenna array axis. Energy received by the antenna array 74 is selectively abstracted by the individual antenna array elements A, B, C and D. The wave energy abstracted by each individual array element depends upon the angle which each of the antenna array element axes makes with the direction of the received wave energy. Wave energy received by antenna array element A is coupled into symmetry arm 78, wave energy received by antenna array element B is coupled into symmetry arm 88, waveguide energy received by antenna array element C is coupled into symmetry arm 80, and wave energy received by antenna array element D is coupled into symmetry arm 86. Hybrid tee 82 will add and subtract the wave energy from its symmetry arms so that sum arm 99 will have an output equal to and dilference arm 81 will have an output equal Similarly, hybrid tee 99 will add and subtract the wave energy received from its symmetry arms so that sum arm 100 will have an output equal to and difference arm 91 will have an output equal to Hybrid tee 96 will add and subtract the wave energy from its symmetry arms so that sum arm-106 will have an output equal to and difference arm 188 will have an output equal to "Similarly, hybrid tee 94 will add and subtract the nave energy received by its symmetry arms so that sum arm will have an output equal to V V+ The ditferenee arm 98 is not required for simultaneous lobing.

Fig. 6 and Fig. 8 are simultaneous lobing antenna array systems in accordance with this invention using an alternative method of obtaining the sum and the difference signals from the antenna array elements. Fig. 6 is a two-dimensional array designed for simultaneous lobing in a single plane and Fig. 8 is a two-dimensional array designed for simultaneous lobing in two perpendicul ar planes.

Fig. 6 is a two-dimensional antenna array system wherein a plurality of waveguides are placed side by side defining a two-dimensional array 120. One side of array is provided with columns and rows of radiation slots 124 for the interchange of wave energy between the array and space. Waveguides 126 are coupling waveguides and are slot coupled at their respective centers to the ends of the array waveguides 122. Wave energy is exchanged between the waveguides 126 and the waveguides 122 by the coupling slots 128. A sum feed 130 and a difference feed 132 each containing diagonal coupling slots 134 are slot coupled respectively to the ends of the waveguides 126.

Fig. 7 is a more detailed view of the sum feed 130 and the difierence feed 132 showing the orientation of the coupling slots 134. The center line dividing the array of Fig. 6 into two equal parts is shown in Fig. 7 as the center line 136. The sum feed 130 has slots which are symmetric with respect to the center line 136. The difference feed 132 has slots which are non-symmetric andwhich provide a 180 degree phase difference at opposite sides of center line 136. Therefore wave energy radiated by the difierence feed 132 will have a phase dilference of 180 degrees at opposite sides of the center line,136.

Referring again to Fig. 6 and making use of the nomenclature of Fig. 4, the antenna array 120 may be considered as divided into two equal array elements, A and separated from one another by the center line 136 of Fig. 7. Wave energy supplied to the sum feed 130 is coupled into the array 120 without any phase change and radiated into space along the array axis. Wave energy received by antenna array 120 may be thought of as being received by the two array elements A and B. The wave energy coupled into sum feed 130 provides an output signal equal to since no phase change occurs. The wave energy coupled into the difierence feed 132 provides an output signal equal to (A-B since a 180 degree phase changeoccurs on difierent sides of the center line of the difference feed. The output signals of the system of Fig. 6 therefore provide output signals similar to the systems shown in Figs. 1, 2, and-3.

Fig. 8 is a modification of the two-dimensional array systemof Fig. 6 and capable of lobing in two perpendicular planes. A plurality of waveguides 142 are placed side by side defining a two-dimensional array 140. One side of the array is provided with columns and rows of radiation slots 144 for interchange of wave energyJbetween the array and space. A first sum feed 146 and a diflference feed 148 are coupled respectively to opposite guides and are slot coupled regarded as .uniformly along the array axis.

I shown in Fig. with the use i It is to be understood that the above depicted combina tions of this-combination may be made within the scope Although the simultane ures'containseries slots, any .other displaced slots or edge slots may be if proper reorientation of the members of the waveguide structures is provided. Furthermore, from the above illustrated invention are not confined to at their respective ends to the centers of the array waveguides 142, by the coupling slots 152. A second sum feed 154 is slot coupled to the other end of the coupling waveguides 150 by a set of diagonal slots 156. The effect of the second sum feed 154 may be electrically subdividing the antenna array elements A & B and C & D into still smaller array elements along the horizontal plane containing the axis of the second sum feed 154. The array elements are designated A, B, C, and D in conjunction with the nomenclature adapted in Fig. 4. To. energize the array, wave energy supplied to the first sum feed 146 is coupled into the array waveguides 142 causing the array 140 to radiate Wave energy received by the antenna array 140 may be considered as being rcceived by the four antenna array elements A, B, C, and D. The wave energy coupled into the sum feed 146 provides an output signal equal to ABCD. The wave energy coupled into the difference feed lliprovides an output signal equal to (AB) -'-(CD). The wave energycoupled into the second sum feed provides an output signal equal to (A C)-(BD). The output signals of the system of Fig. 8 therefore provides output signals similar to the system ofhybrid tees.

tion of antenna arrays and unidirectional couplings are representative of the invention and are not to be interpreted in a limiting sense since many possible modificaof the hereto appended claims. ous lobing antenna array systems shown in the above figslots such as laterally substituted therefor.

the signals derived the use of amplitude comparison monopulse systems but may be applied equally successfully to phase comparison monopulse antennas.

What is claimed is:

1. A simultaneous lobing array for monopulse opera- V tion in two dimensions comprising: a plurality of linear waveguides arranged in parallel in a common plane and coextensive with each other, each of said linear waveguides having a plurality of radiating apertures extending lengthwise therealong in a common surface on one side of the array thus formed to provide columns and rows of radiators; conductive dividers centrally positioned in said linear waveguides and separating the array into top and bottom halves; a group of feed waveguides, saidT feed Waveguides being divided into two pairs of colinear waveguides which are centrally spaced apart, each pair of colinear feed waveguides lying along a line normalto the linear waveguides at a different end of the waveguide array and being coupled to waveguides for transferring energy therewith; a first pair of hybrid junctions, each positioned between a different one of the colinear pairs of feed waveguides and having symmetrical terminals coupled to the individual feed waveguides and also sum and difference terminals, the cou-l pling of the feed waveguides with the difference terminals further dividing the array into halves to define four quadrants; and an additional pair of hybrid junctions, each having sum and difference terminals and symmetry terminals, with the symmetry terminals of one of the additional pair being coupled to the difference terminals of both of the first pair of hybrid junctions, and the symmetry terminals of the second of the additional pair being coupled to the sum terminals of both of the first pair of hybrid junctions.

2. A simultaneous lobing antenna system for providing simultaneous two dimensional information for tracking a target and comprising: a plurality of linear waveguides arrangedin parallel in a common plane and adjacent to 75 each other, each of said waveguides having a number of radiating apertures disposed in a column along the length (thereof, with the radiating apertures being disposed on across the waveguides; a plurality of conductive interface members, each positioned at a central point within adifferent one of the linear waveguides and dividingthc columns of radiating apertures into halves; a group of four feed waveguides, each of said feed waveguides extending across a group of linear waveguides parallel to the rows of radiating apertures, said feed waveguides being grouped incolinear pairs which are centrally spaced apart, each of the pairs being associatedwith a different waveguides and each having sum and difference terguides.

minals; and a second pair of energy couplers, each symmetrically connected between a different like pair of sum and difference terminals from the first pair of couplers and each having sum and difference terminals for providing thereby energy representative of algebraic summations of quadrantally'derived energy from the linear wave- 3. A simultaneous lobing antenna system for-lobing in at least one dimension and comprising: a plurality of linear waveguide elements arranged in parallel in a common plane to define a radiating array, each of said waveguide elements having a plurality of apertures spaced the individual adjacent linearlengthwise along a-like surface thereof and defining colurns and rows of radiating apertures; at least a pair of, feed waveguides extending across said linear waveguide elements and normal thereto, each of said feed wave guides being coupled to transfer energy to each of said linear elements at given points; and means coupled to said pair of the feed waveguides for providing a signal proportional to the difference between the energies in said waveguide elements on each side of a centerline of the radiating array.

4. A simultaneous lobing antenna system for lobing in two dimensions and comprising: a group of linear Waveguide elements arranged in parallel in a common plane to define a radiating array, each of said waveguides having radiating apertures spaced along a like surface thereof, the apertures in each waveguide defining columns of apertures, and like positioned. apertures across the waveguides defining rows of apertures; a first sum feed waveguide coupled across the radiating array parallel to the rows and at one end thereof and having coupling apertures for providing in-phasc transfer of energy between said sum feed waveguide and each of the waveguides of said array; :1 difference feed waveguide coupled to the radiating array at the other end thereof from the sum waveguide and having radiating apertures coupled to each one of the linear waveguides, the phase disposition of the apertures in the difference waveguide eltectively dividing the rows of radiating apertures into halves to provide diiference signals; and -a second sum feed waveguide positioned across the linear waveguides of the radiating array in approximately the center thereof, and having apertures providing inphase coupling the second sum feed waveguide to 'the linear waveguides of the radiating array, the disposition of the second sum feed waveguide effectively dividing the columns of radiating apertures into halves.

2,585,173 Riblet Feb. 12, 1952 2,825,057 Worthington Feb. 25, 1958 2,830,288 Dicke Apr. 8, 1958 like surfaces of the waveguide and in rows extending.

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