Research On Passive DOA Estimation Technology Of Underwater Weak Target Based On Interference Suppression

Due to the influence of underwater strong interference background,the research on weak target azimuth estimation is always an important problem in underwater acoustic signal processing.Based on adaptive interference cancellation,spatial matrix filtering and adaptive spatial matrix filtering,this paper studies the interference suppression technology of linear array in order to improve the azimuth estimation performance of passive sonar for weak targets.Firstly,this paper studies the interference suppression technology based on adaptive cancellation.The techniques of post beamforming interference cancellation,adaptive array element domain interference cancellation and frequency domain adaptive interference cancellation are studied.The simulation results show that under narrowband interference,the post beamforming interference cancellation and adaptive array element domain interference cancellation have good performance of interference suppression and target azimuth estimation;under broadband interference,post beamforming interference cancellation can not produce effective suppression,while frequency domain adaptive interference cancellation can suppress interference and has high azimuth estimation accuracy;under the condition of broadband multipath,frequency domain adaptive interference cancellation can realize anti multipath processing of broadband signal,and the performance of azimuth estimation is good.Secondly,based on the fact that it is difficult to obtain ideal reference input by adaptive filtering method,the interference suppression technology of spatial matrix filtering is studied in this paper.The design criteria and solution methods of three spatial matrix filters are studied.The simulation shows that the number of array elements,passband width,passband position and stopband attenuation will affect the filtering effect of the matrix filter.The passband response error and stopband attenuation of the filter should be comprehensively considered,and the appropriate filter parameters should be selected.In addition,the interference can be effectively suppressed after spatial matrix pre filtering,and the target azimuth estimation performance is good.Finally,aiming at the decline of target azimuth estimation performance of conventional spatial matrix filter with low stopband attenuation in the background of strong interference,the interference suppression technology of adaptive spatial matrix filter is studied in this paper.Adaptive spatial matrix filter,notch broadening adaptive spatial matrix filter,dimension reduction adaptive spatial matrix filter and coherent signal adaptive spatial matrix filter are studied.The simulation results show that compared with the conventional spatial matrix filter with low stopband attenuation,the adaptive spatial matrix filter has better strong interference suppression performance and improves the performance of target azimuth estimation;when the jamming azimuth changes suddenly,the adaptive spatial matrix filter processed by broadening and zeroing has better azimuth estimation performance for two targets;the azimuth estimation performance of the reduced dimension prefilter based on discrete ellipsoid sequence is slightly lower than that of the non reduced dimension processing,but the amount of calculation is greatly reduced;the adaptive spatial matrix filter combined with spatial smoothing can suppress coherent interference,and the azimuth estimation performance is good.The experimental data processing further verifies the effectiveness of the adaptive spatial matrix filter interference suppression algorithm.