AUTOFOCUSING TECHNIQUE FOR ADAPTIVE COHERENT SIGNAL-SUBSPACE TRANSFORMATION BEAMFORMERS

The coherent signal-subspace transformation (CST) wideband beamformer, which integrates the alignment of all frequency components and a freq uency-independent weight network, has the capability of handling multi path or coherent wideband signals. If accurate preliminary focusing an gles are not available due to, for example, the presence of nonstation ary sources or the use of nonbatch processing, it becomes necessary to use the adaptive version of the CST wideband beamformer. The proposed adaptive CST wideband beamformer includes adaptations of frequency-in dependent weights and focusing angles. Because the frequency-independe nt weights can be easily adjusted, using many adaptive procedures whic h have been proposed for narrowband beamformers, the adaptation of the focusing angles is the essential function of the adaptive CST beamfor mer to null correlated and uncorrelated interferences. The authors pro pose an autofocusing technique to simultaneously improve the accuracy of focusing angles and meliorate the performance of CST beamformers.