Stochastic Effects in Adaptive Null-Steering Antenna Array Performance

A new average equation for the adaptive weights which takes into account the effects of statistical weight fluctuations has been developed. Past researchers have derived results by using an approximate average equation for the weights obtained under the assumption that the weights vary much more slowly than the input process. The weights are then treated as constants for averaging. The new method employs a two-variable perturbation analysis which uses as a small parameter the ratio of the loop bandwidth to the input process bandwidth. The analysis yields a significant correction term for the directivity pattern in interference nulls. This correction term is the result of stochastic weight fluctuations which are usually ignored in most analyses. Comparison of these results to those found by past researchers is given and the results of a computer simulation substantiate the analysis.