“…In addition, methods such as incoherent signal subspace method (ISSM) [9], coherent signal subspace method (CSSM) [10] and test of orthogonality of projected subspaces method (TOPS) [11] have also been proposed. Recently, with the development of compressive sensing theory [12,13], many sparsity based DOA estimation methods were developed [14,15,16,17], including various extensions to the wideband case [18,19,20].…”