Coherent signal-subspace processing in a sector

The determination of the number of wideband signals impinging on a passive sensor array in the form of multiple groups (clusters), and the estimation of their directions of arrival is addressed. The idea of preprocessing by a set of orthogonal beamformers for dimensionality reduction is used to simplify wideband processing. The effectiveness of this approach is demonstrated with the use of discrete prolate spheroidal sequences (DPSSs) as the beamformers for linear uniform arrays. A weighting gain as an indicator of the improvement in the signal-to-noise ratio due to such preprocessing is introduced. Two versions of an algorithm that combines preprocessing/prefiltering and the coherent signal subspace method in the frequency domain are developed, and comparative performance evaluations are carried out. The relative effects of beamspace prefiltering on optimum and suboptimum estimators are explored