Impedance properties of antenna arrays

An analysis is presented of the impedance properties of typical radiating elements in large arrays. An array of slots is treated first, where each slot is fed by a separate waveguide and the array radiates into a half-space. The slot spacing and progressive phasing in the array may be arbitrary, however. Both the slot and susceptance are evaluated; a periodic structure point of view is employed which permits a waveguide-type analysis of the half-space region. The results yield information on the efficiency of the array, its gain, its reactive content, its mismatch, and the variation of all of these quantities with arbitrary scan angle. By appropriate duality and normalization considerations, corresponding impedance expressions are obtained for an array of dipoles located in free space, backed by a ground plane, or in the environment of baffles. Of particular interest here is the change in the dependence on scan angle due to the presence of baffles or the ground plane. Comparison is made with the literature in certain special cases.