Mode excision adaptive beamforming for source detection in an uncertain shallow‐water waveguide

Passive sonar detection is uniquely characterized by the fact that the acoustic clutter distribution is generally confined to the ocean’s surface. There is considerable evidence to support the hypothesis that surfaced and submerged sources are well separated in acoustic mode space, and that shallow‐water waveguide normal modes are relatively robust to imperfect environmental knowledge. In this work, the use of mode physics is explored for the purpose of identifying an improved adaptive subspace for submerged source detection in the presence of surface interference. The basic premise is to perform adaptive weight computation in a mode subspace that is weakly excited by the submerged source of interest, yet well coupled to the surface interference. The rationale is to excise as much of the target signature as possible from the sample covariance without excessively compromising the measurement of the interference spatial spectrum. This enables more aggressive nulling of the surface clutter spectrum for a giv...