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Requirements for a broad-band, steerable linear antenna array are given. The limitations due to grating lobes of an equally-spaced array are discussed. Results are given of the study of several different unequally-spaced arrays which have two advantages: 1) fewer elements for comparable beamwidth; 2) grating lobes and minor lobes replaced by sidelobes of unequal amplitude which are all less than the main beam. A scheme for controlling the cosine arguments in the radiation pattern formula is given which has resulted in one of the best patterns of this study of unequally-spaced arrays. The universal pattern factor was computed for an array having a set of spacings determined by this scheme. This array is capable of steering a beam 90 over a 2-to-1 frequency band with no sidelobe above -5 db. It uses 21 elements, compared to 78 for an equally-spaced array of similar beamwidth. The results obtained indicate that further study of the controlled cosine method and unequal spacing in general should result in better pattern characteristics.
King et al. (Fri,) studied this question.