Coherent wideband DOA estimation of multiple FM signals using spatial time-frequency distributions

The previously developed concept of narrowband spatial time-frequency distributions (STFDs) is extended to the wideband case. A new STFD-based root-MUSIC estimator is proposed. This estimator exploits a short-window spatial pseudo Wigner-Ville distribution (SPWVD) to enable application of the subspace-based approach. To combine all relevant SPWVD points, the proposed technique employs an extended coherent signal-subspace (CSS) principle involving coherent averaging over a pre-selected set of time-frequency points rather than the conventional frequency-only averaging procedure.