Direct Wave Interference Suppression Method with Sparse-Sidelobe Constraint in Bistatic Sonar

In order to suppress the strong direct wave interference in the bistatic sonar system, this paper proposes a method that combines the weighted sparsity-constrained capon beamformer with the zero constraint. The algorithm uses the sparse distribution of beam response and adds sparse constraints (l
1
-norm constraints) in the side lobe. By using the orthogonal characteristics of the signal subspace and the noise subspace, a weighted matrix is constructed to weight the sparsity constraint. Subsequently, the optimal weight can be derived by minimizing the output power. In the bistatic sonar system, according to the prior knowledge of the system configuration, the direction of direct wave is often known. Based on the fact, the zero constraint is used to set the beam output response of the array form to be a null in a fixed direction. Under the constraint of null, a least-square method is exploited to approximate a constraint pattern to an ideal pattern in order to solve the optimal weight. Consequently, a deeper and wider null is generated, which improves the anti-steering vector angle mismatch of the array ability. In the case of small deviations in the direction of the interference wave, the receiver can also effectively suppress the interference.