Robust coherent signal-subspace processing for directions-of-arrival estimation of wideband sources

The authors propose a class of robust focusing matrices for the coherent signal-subspace method, a novel approach for the estimation of directions-of-arrival of wideband sources. The new class of focusing matrices has robustness against size variations of focusing sectors obtained by preliminary group angle estimates. To quantify information loss due to source focusing, a new measure, termed `relative efficiency index´, is introduced and its properties are proved. This index is then used to assess statistical sufficiency of the coherently averaged covariance matrix, a data-reduced statistic on which the coherent signal-subspace method is based. Sensitivity issue as well as estimation performance comparisons for various classes of focusing matrices, based on simulations and relative efficiency index, are also presented