An approach to adaptive beam-forming for wide-band systems using a subband decomposition

The purpose of this work is to introduce two variations of an approach to adaptive beam-forming for wide-band sensor array systems using a subband decomposition. Subband decomposition facilitates a computational complexity efficient approach to the adaptive beam-forming problem. We derive optimal adaptive weights in the subband domain using two optimality criteria: (a) maximum SINR, and (b) minimum MSE. It is shown that, unlike the narrow-band case where these criteria yield the same weights up to an overall multiplicative constant, here the two criteria result in different adaptive weights. Explicit conditions for this approach are given. Further, an approach for avoiding spatial mismatch errors is shown.