Robust Beamforming Method Based On The Horizontal Array Under Shallow Sea Channel

Due to the reflection of the sea surface,the sea bottom and the refraction in the seawater medium layer,the acoustic signal received by any receiving point in the ocean is the superposition of acoustic signals passing through different propagation paths under the shallow water acoustic channel which is complicated,thus forming the multipath effect of acoustic signal propagation in shallow seawater.The multipath effect in the shallow sea leads to errors in the estimation of the desired signal steering vector through the traditional DOA estimation methods,and seriously affecting the target bearing estimation performance of the system.This paper focuses on the realization of robust target bearing estimation based on the shallow sea channels.Firstly,the characteristics of channel transmission in shallow water are briefly summarized,the cause of multipath effect is discussed emphatically and the impact of multipath effects on target azimuth estimation under different sound speed gradient changes,various locations of transmitters and receivers and different incidence azimuth conditions is quantified.Secondly,this dissertation do theoretical research and simulation analysis of the robust beamforming algorithm under the scalar array and the vector array based on the ideal environment.The vector array signal processing model based on independent proce-ssing and joint processing are also discussed respectively.By comparing the robustness of algorithms with amplitude and phase errors and different snapshots,the Robust Capon Beamforming(RCB)algorithm and the worst-case performance optimization can achieve performance improvement and certain robustness when the steering vector is mismatched.Compared with the scalar array,the vector array can pick up more information,so the output performance of the vector array based on joint processing vector array has higher angle estimation accuracy and lower background spectrum level.Finally,robust beamforming algorithms based on shallow sea multipath channels is studied.The shallow sea horizontal array signal processing model is established based on the characteristics of multipath effects in shallow seawater,and it is discussed in combination with the RCB algorithm and the worst-case performance optimization.The robustness of algorithm under different conditions is simulated and analyzed,and the distortions caused by the multipath effect are corrected by imposing the constraints,which makes the performance of robust beamforming algorithms in the complex shallow sea environment improved.