A UNIFIED APPROACH TO THE DESIGN OF LINEAR CONSTRAINTS IN MINIMUM VARIANCE ADAPTIVE BEAMFORMERS

This paper describes a simple, systematic procedure for designed linear constraints in minimum variance beamformers which allows an arbitrary specification of the quiescent response-the beamformer response when only white noise is present. In this approach, the first constraint is dedicated to the imposition of a desired quiescent response, and additional constraints are included to assure proper reception of the desired signal. The function of these additional constraints is to make the overall beamformer response equal the quiescent response in the desired signal region so that the signal is not cancelled when it is present. Optionally, the response can also be fixed in other regions of interest by adding more constraints. This design procedure clearly demonstrates that the key to designing efficient constraints lies in finding the weighting coefficients which specify the desired quiescent response-a problem identical to the synthesis of desired beam patterns for nonadaptive arrays. Using two recently developed algorithms to synthesize desired quiescent responses, the effectiveness of this new design procedure is illustrated by examples in both narrow-band and broad-band arrays.