It is well known that the single line comes from left or right. Multi-line array provides array sonar can＇t identify whether the target the possibility to solve the left-right ambiguity problem. The performance of left-right resolution for twin-line array is described in this paper. It is shown that the suppression ratio, which is defined as the ratio of the response in the steering direction to opposite symmetrical direction, can be considered as an index for evaluating the ability of solving left-right ambiguity. The characteristics of suppression ratio is discussed. The theoretical expression for suppression ratio and some numerical results are illustrated. The result of theoretical analysis can be used in design of twin-line array sonar.
The spatial matrix filter was designed and used for solving the problem to detect a weak target who was influenced by the strong nearby platform noise interference of the towed line array sonar. The MFP technology and the DOA estimation technology were combined together by using the sound propagation characteristics of both target and interference. The spatial matrix filter with platform noise zero response constraint was designed by the near-field platform noise normal modes copy vectors and the far-field plane wave bearing vectors together. The optimal solution of the optimization problem for designing the spatial matrix filter was deduced directly, and it was simplified by the generalized singular value decomposition. The total response error to the plane wave bearing vectors and the total response to the platform noise copy vectors were given. The phenomena that strong interferences existed in the bearing course and blind areas existed after filtering were analyzed by the correlation between the plat- form noise copy vectors and the plane wave bearing vectors. It could be found from simulations that it has less blind area and higher detection ability by using the spatial matrix filtering technology.
