Focusing matrices for wideband array processing with no a priori angle estimates

A class of data transformation matrices is introduced for the estimation of angles of arrivals of multiple wideband sources. The proposed transformation matrices are unitary and minimize the average of the squared norm of the focusing error over the angles of interest without prior knowledge of source locations. They can also be used with the multigroup sources and lead to lower resolution thresholds than those obtained with other techniques. A comparison of the statistical performance of the proposed focusing procedure with that of the spatial resampling method is provided