A multiple-beam two-dimensional waveguide slot array

Considerations affecting the design of traveling-wave slot arrays which may be fed from either end to produce symmetrical beams are presented. The application of this approach to the design and construction of two-dimensional waveguide slot arrays is described. The arrays designed are capable of producing a pencil beam in each of 4 directions, when fed from each of 4 ports. The beams are symmetrically located, to a high degree of precision, about the normal to the array. Such an antenna finds application in fixed-beam doppler radar systems. Problems discussed are those of obtaining low sidelobes and high aperture efficiency. In the solutions presented, near-in sidelobes were reduced to the 20-25-db level, but internal reflection of power not radiated by the traveling-wave array led to "image sidelobes" which were of the order of 15-17 db. Also discussed are practical problems such as construction methods, reduction of beam shift with temperature, reduction of humidity effects on gain, and effect of tolerances on beam symmetry.