Study On Key Technologies Of Multistatic Active Sonar

With the development of noise reduction technology and high-thrust,low-speed propeller technology and anechoic tiles,the target intensity and radiation noise intensity of ships have decreased,making the traditional single base sonar,as well as pure passive sonar in the detection of underwater targets many bottlenecks are increasingly highlighted.This has led to the creation of multi-base active sonar systems.Multi-base active sonar system has the advantages of both active and passive sonar,and has significantly improved in concealment,detection range,anti-interference capability,and flexibility of configuration.However,the receiving base is affected by direct waves in the process of operation,and the towed array is inevitably affected by real-time factors such as tugboat motion and currents during the towing process,resulting in distortion of the array shape.Therefore,this paper focuses on two key technologies:towing array calibration and direct wave suppression,in the active detection mode of multi-base.Firstly,the basic theory of bistatic/multistatic active sonar is studied,the configuration mode of bistatic sonar system is introduced,and the parameters in the configuration of bistatic sonar system are defined.The Doppler principle in bistatic sonar system is introduced.The sonar equation of bistatic active sonar is introduced.Based on the sonar equation,the SNR and SIR of target echo are deduced.The detection range of bistatic/multistatic sonar and the masking area of direct wave are further analyzed.Secondly,in order to estimate the flexible horizontal array parameters of the receiving base in the active mode of bistatic system,a new method using direct wave as calibration source to estimate the array parameters of the receiving base is presented.For possible echo interference,FRFT is used to extract direct wave,and on the basis of signal extraction,the parameters of the array are estimated.The near-field spatial spectrum of the radiated noise of the towing ship is used to solve the fuzzy problem of the array estimation.Compared with the traditional parameter estimation methods,the algorithm suppresses the signal interference,improves the estimation accuracy of the array parameters,and has a strong tolerance to noise and interference,incident angle error,Doppler frequency shift.The feasibility of the array parameter estimation method is verified by the actual data processing results.Finally,for the direct-wave interference suppression problem,this paper first simulates and analyzes the spatial filter class algorithm,and finds that when direct-wave is suppressed,the sector blind area generated affects the target detection in the area at the same time,in order to reduce the blind area of direct-wave suppression.The acoustic shielding method is used to achieve point shielding,but it is difficult to apply it in practice because the shielding factor of the corresponding channel is generated based on the accurate estimation of the direct wave acoustic channel.Therefore,this paper presents a method to suppress the direct wave and detect the target echo by using the Doppler difference between the direct wave and the target echo,and to suppress the direct wave by using the Doppler sensitive signal in the spatial Doppler frequency shift domain.Finally,the time delay and Doppler information of the target echo can be accurately estimated by a multichannel filter.