A modified LMS algorithm for use with a hybrid analog/digital adaptive beamformer

This paper presents a modified LMS adaptive algorithm which controls a hybrid analog/digital adaptive beamforming system. The proposed beam-former structure is unique in that simple analog filter elements are employed in the beamformer. Each filter consists of a tapped-delay-line in which the taps are switches taking on values of -1, 0 or +1. A 'virtual' weight vector is retained in an off-line digital processor, which is adjusted using samples taken from the analog beamformer. A simple and unique method is used to convert the switches in the analog filter elements. The algorithm used to control this structure is presented here using a geometrical approach. Experimental results confirming the predicted performance of the beamforming system are also presented.