Broadband high-resolution direction-of-arrival estimation using beamspace coherent signal subspace approach

Frequency-domain and time-domain beamspace preprocessing approaches to direction of arrival (DOA) estimation for multiple broadband far field signals are proposed. A set of beamformers with constant main beam response is designed to cover the angular sector of interest. The array snapshots are passed through the beamforming preprocessors prior to application of MUSIC. The time-domain processing is computationally less expensive since it eliminates the need for frequency decomposition. For the scenario of strong out-of-band interfering sources, our approach can form nulls or notches in the direction of them and guarantee that the main beam response of the beamformers are constant over the design band. Numerical results show that the proposed time-domain processing has comparable performance with the frequency-domain processing method, and both of them are able to resolve correlated source signals and provide lower resolution threshold and lower root mean square error (RMSE) of estimate compared with the existing methods. Our beamspace DOA estimator maintains good DOA estimation and spatial resolution capability in the scenario of strong out-of-band interfering sources.