Research On The Direction Finding Method Based On The Wide Aperture Acoustic Array

With the development of underwater joint combat system equipment,submarine has become an important part of it.As one of the main acoustic arrays of submarine sonar system,wide aperture acoustic array plays an irreplaceable role.Therefore,the research of passive direction finding based on wide aperture acoustic array is bound to become one of the important research directions of underwater acoustic signal array processing.With the vigorous development of vibration and noise reduction technology in the world,not only the self noise level of sonar platform decreases year by year,but also the radiation noise level of submarine itself.Therefore,the ability of passive direction finding based on wide aperture acoustic array also decreases.In order to improve the passive direction finding ability of sonar system,the existed passive direction finding methods need to be optimized and improved.Firstly,the acquisition of space and time gain can be improved,and the signal-to-noise ratio of array signal can be improved;Secondly,the ability of weak target detection is improved by enhancing the cancellation and suppression of strong interference in fixed azimuth;Finally,the acquisition and analysis of the enemy's pulse signal should be strengthened to enhance the ability of pulse reconnaissance.At last,by combining the above processing methods,the improved fusion processing can improve the passive direction finding ability based on wide aperture acoustic array.The main contents of this paper are as follows1.The development history of passive sonar is summarized,the wide aperture acoustic array and acoustic propagation model are established,and the principle and physical basis of azimuth estimation are studied.The received signal of array element is processed by conventional beamforming,cross-correlation time delay difference estimation and post integration to obtain the space gain and time gain,improve the signal-to-noise ratio of the array element signal and realize the target azimuth estimation.2.In the process of passive sonar azimuth estimation,the propeller and mechanical rotation noise of the platform itself will produce fixed azimuth interference targets in the detection sector,which will inevitably affect the sonar's detection of long-distance weak targets,resulting in a sharp decline in the accuracy of sonar azimuth estimation or the loss of azimuth estimation ability.In this paper,Bartlett beam null algorithm is used to sag the azimuth beam response of strong jamming,which reduces the jamming response and improves the detection ability of sonar for weak targets.3.Usually,the azimuth estimation of the enemy target can be realized not only by the noise signal received by the wide aperture acoustic array,but also by the pulse signal received.In this paper,precise pulse front detection technology and conventional beamforming technology are used to improve the azimuth estimation accuracy and detection ability of pulse detection module.4.The signal processing methods such as conventional pre beamforming,null pre beamforming,cross-correlation time delay estimation,post integration,line spectrum enhancement and pulse front detection are realized by simulation.The improved passive direction finding method is verified by combining the directivity function,beamwidth and azimuth estimation results,Through the sea trial data processing,the processing effect and feasibility of the improved pulse front detection technology are verified,which lays a solid foundation for the subsequent engineering application of the algorithm.