Direction of Arrival Estimation Based on Low-Rank Matrix Processing

To address the performance degradation of traditional adaptive beamforming algorithms in low signal-to-noise ratio (SNR) marine environments, a weighted nuclear norm minimization optimized minimum variance distortionless response beamformer (WNNM-MVDR) is proposed. The method integrates low-rank matrix processing with beamforming and applies singular-value-dependent weighting to the sample covariance matrix, thereby retaining dominant signal components while suppressing noise-subspace components. The shrinkage parameter is initialized using a random-matrix-theory estimate of the upper edge of the noise spectrum. Simulation and sea-trial results evaluate the method under limited snapshots, array mismatch, varying SNRs, and coherent multipath. Under ideal conditions without array mismatch and with sufficient snapshots, the algorithm consistently achieves an output SNR gain of more than 4 dB for input SNRs above −20 dB. Sea-trial results further show a 1.68 dB output SNR improvement over conventional MVDR, a 2.67 dB extension of the practical weak-target detection limit, and reliable robustness to array-position errors up to 0.204 wavelengths. These results indicate that WNNM-MVDR can improve adaptive beamforming performance in the marine scenarios considered here.