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 frequency-independent weight network, has the capability of handling multipath or coherent wideband signals. If accurate preliminary focusing angles are not available due to, for example, the presence of nonstationary 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-independent weights and focusing angles. Because the frequency-independent weights can be easily adjusted, using many adaptive procedures which have been proposed for narrowband beamformers, the adaptation of the focusing angles is the essential function of the adaptive CST beamformer to null correlated and uncorrelated interferences. The authors propose an autofocusing technique to simultaneously improve the accuracy of the focusing angles and meliorate the performance of CST beamformers.<>