Minimax optimization of two-dimensional focused nonuniformly spaced arrays

Recently there has been interest in applying the results of digital filter design theory to the optimization of the beam forming pattern of antenna arrays. The techniques employed usually involve minimax criteria for side lobe suppression. Certain applications require focused operation in order to make use of the near field for imaging. Nonuniform array element spacings have been successfully employed to reduce side lobes in phased arrays and to minimize the number of elements. Presented here will be a combination of nonuniform spacing, focusing, and element shading using some optimizing window designs to form a narrow center beam with very good side lobe suppression. The treatment is unique in that it explicitly incorporates the effects of focusing in the optimization procedure.