Wideband focusing using spatial-delay filters for direction-finding

For wideband direction-finding related to wideband-source location estimation, the coherent signal-subspace method has been found to be more effective than the incoherent or frequency binwise processing method, and to achieve lower detection and resolution thresholds. The method involves a preprocessing step of focusing signal spaces at different frequencies to a common frequency, and a narrowband direction-finding algorithm following the preprocessor. For uniform linear arrays focusing corresponds to spatial delay implementation. In the present work, least squared error and maximally, flat FIR (finite impulse response) filters for realizing the spatial delay are designed. Simplified implementations that reduce computational complexity are also proposed. The effectiveness of these filters is confirmed by computer-simulation experiments