Adaptive array performance with multipath interference

We consider the performance of adaptive arrays subjected to multipath interference. The multipath signals are assumed to originate from the same transmitter but to arrive at the adaptive array from different directions with different time delays and different frequency shifts. For such interference the differential frequency shifts on the multipath signals result in a nonstationary covariance matrix, so the optimal array weights are time varying. The rate of variation of the optimal weights is determined by the multipath frequency shifts.