Phase-Only Adaptive Nulling with Discrete Values

A method, using a branch and bound algorithm, is described for obtaining optimal phase settings for jammer cancellation with an electronically scanning array (ESA) whose only variable parameters are element phases which vary in discrete steps. Methods of continuous analysis cannot produce the complex element weight vector, W, that maximizes the signal to interference plus noise ratio (SIR) for a linear array if the components of W are restricted to a discrete set. Moreover, an exhaustive search is impractical. In contrast, the branch and bound technique needs to examine only a small subset of all possible discrete weight vectors in order to arrive at the best SIR. The method has been tested with a few examples. The jammer cancellation results in these cases have been encouraging.