A MULTIPLE TIME-SCALE MODULARIZED ADAPTIVE BEAMFORMER

This paper analyzes the cascaded equivalent form of the minimum varian ce distortionless response (MVDR) beamformer. A unique feature of the modularized MVDR (M2VDR) beamformer is the ability to distribute adapt ive degrees of freedom (DOF) among beamformer stages. This property of the M2VDR beamformer allows DOF to be adapted over different time sca les. As a consequence of the multiple stage decomposition adaptive bea mformer weights appear in a form which suggest an apparent increase in the number of DOF. To properly analyze this case an alternative inter pretation of adaptive DOF is introduced to establish the equivalence b etween the MVDR beamformer and its cascaded realization. In the second part of this paper the distribution for the output power estimate of a P stage M2VDR beamformer is derived. Analysis reveals the necessity of placing constraints on the adaptation time assigned to each beamfor mer stage. Simulation experiments are presented that demonstrate the a pplicability of the M2VDR beamformer in resolving closely spaced sourc es under impulsive interference conditions.