Methods for null control and their effects on the radiation pattern

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.