A Near-Field Interference Recognition Method Based on Split Beam

Beamforming is a fundamental technique in array signal processing, and it is widely used in underwater acoustic target detection and parameter estimation. The beamforming performance degrades severely in the presence of sonar platform interference. In fact, the interference source of the sonar platform radiates as a near-field spherical wave, and thus the time delays from the source to the array sensors would vary with both its distance and azimuth. However, the target signal of interest can be processed as a far-field plane wave. The time delays of the far-field signal are only dependent on the target azimuth when the distance from the target to the array is much larger than the array aperture. In this paper, a novel method is proposed to discriminate between far-field target signal and near-field interference by exploiting the difference in split beam patterns between the two. The feasibility of the proposed method is verified by Monte Carlo simulations.