Sidelobe-reduction techniques for phased arrays using digital phase shifters

Through the introduction of a new parameter the radiation pattern of a phased array using digital phase shifters for beam steering can be made periodic, and pattern considerations can be confined to a very narrow range of the scan angle. Arrays designed on the basis of a least mean-square pattern error are shown to require the smallest absolute values of a phase-index function. A systematic and easy-to-apply method is developed for reducing the peak sidelobes of nonreciprocal phased arrays by one-step phase adjustments in certain elements. The amount of possible sidelobe reduction depends on the scan angle and the size of phase-quantization steps. Typical examples for 4-bit phase shifters show that reductions in excess of 9 dB are possible for certain main-beam directions.