Research And Implement On Robust Beamforming Algorithm Based On Towed Array

The towed line array is widely used in underwater engineering due to its advantages of large aperture,low frequency,and long detection range.The shore-based sonar is not adjustable,and the side of the ship is susceptible to the noise of the ship.Therefore,the advantage of using the tow line array is obvious.Normally,the towed line array is assumed to maintain an ideal linear array state,so it is suitable for various adaptive beamforming algorithms,but the actual array of the towed line array is susceptible to various factors,resulting in formation distortion,and due to the presence of tugboats.Noise and various strong interference sources can also cause the problem of missing targets of the towed line array.Therefore,it is necessary to rationally model the array and enhance the robustness and interference suppression capability of the algorithm.Since the robust algorithm based on the tow array is computationally large,the robust algorithm can be implemented on the performance-leading multi-core DSP to greatly improve the sonar work efficiency and enhance the real-time and scalability.Firstly,the problems of the adaptive wideband beamforming algorithm based on drag and sonar are analyzed in practical applications,including array mismatch,insufficient estimation of sampling covariance matrix,strong interference and the influence of tugboat noise.The simulation shows that the classical adaptive algorithm cannot Guaranteed robustness under various conditions,without application conditions.Secondly,for the problem of insufficient steering vector mismatch and data sample estimation,the three algorithms of diagonal loading,weighted norm constraint and covariance matrix fitting are studied.The performance of the algorithm under different sample snapshots and steering vector errors is analyzed.The simulation results show that the covariance matrix fitting algorithm has higher robustness.Two linear array distortion models are established for the matrix mismatch problem.The tolerance of the above three algorithms to the mismatch degree of the two models is verified.The simulation results show that the weighted norm constraint and the covariance fitting algorithm are more robust to the matrix mismatch.Sex.A robust adaptive beamforming algorithm based on zero-sag broadening is studied for the azimuth offset of the tug,the azimuth disturbance of the jamming source and the relative motion of the platform and the interference source.The simulation results show that the algorithm is based on the adaptive algorithm based on diagonal loading to suppress the tug jamming.At the same time,it has stronger suppression ability for fast interference sources.Aiming at the problem of array signal distortion caused by conventional broadband beamformer,a constant beamwidth algorithm with minimum main lobe difference is studied,and its performance is verified by FM signal.The simulation results show that the signal can be well obtained when it is incident from the non-beam main axis.The distortion target signal is added to the zero-sag extension technology to verify the recovery ability of the target signal when there is a broadband tug interference signal.The simulation results show that the tugboat interference has good suppression effect and can effectively reduce the distortion degree of the target signal.Finally,the robust beamformer studied above can suppress the tugboat interference and maintain good performance under the linear array distortion.The software is implemented on the multi-core DSP platform and effectively optimized in software programming and data circulation.The simulation results verify the correctness of the software implementation.The reliability of the software is verified by software testing.It is verified that the robust adaptive beamforming algorithm based on drag matrix can be realized in real time.