A technique to compensate for mutual coupling in a small array is developed and experimentally verified. Mathematically, the compensation consists of a matrix multiplication performed on the received signal vector. This, in effect, restores the signals as received by the isolated elements in the absence of mutual coupling. The technique is most practical for digital beamforming antennas where the matrix operation can be readily implemented.

Several methods for synthesis of array antenna patterns with prescribed nulls are reviewed. Methods based on full amplitude/phase control at each array element and methods with a restricted number of degrees of freedom are compared, with attention focused on the characteristic features of the resultant patterns. These features are largely independent of any algorithm for achieving the nulls, and therefore they also provide a perspective on the performance of adaptive antenna systems, which employ these various control architectures.

A method of sidelobe nulling, which involves perturbing the array illumination phase only, is presented. The general nonlinear problem is linearized by assuming the perturbations to be small, and an analytic solution is derived. Illustrative examples of sinc and Chebyshev patterns with imposed nulls are given.

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