Passive reverberation nulling and echo enhancement with horizontal receiver array in shallow water

Shallow water bottom reverberation model of horizontal receiver array (HRA) was established based on the ray normal mode bistatic reverberation theory. Then, a passive reverberation nulling method based on averaging of forward and backward reverberation subspace was proposed in this paper. The estimated reverberation subspace of a time-windowed segment of data received by HRA can be obtained by averaging the reverberation subspaces that are obtained by DORT method and corresponding to the previous and latter time segment respectively. The reverberation component of the current time-windowed segment data can be suppressed by the projection approach using the estimated reverberation subspace. This method can overcome the non-stationary of the received echo in local time (range) caused by the roughness of the bottom, and the estimated reverberation subspace is closer to the real one. The signal to reverberation ratio of the received echo is enhanced. As a result, the detection and bearing estimation performance is improved. The performance of proposed method was testified by numerical simulations in typical shallow water environment.