Research On Interface Reverberation Of Shallow Sea Of Moving Monostatic Sonar

Monostatic means that the transmit and receive are in the same position.When active sonar works in shallow sea environments,interface reverberation is one of the main distractions.Interface reverberation includes undersea reverberation,sea surface reverberation.For active sonars such as torpedo homing sonars,the form of the transmitted signal is usually known,and due to the high speed of the platform carrying the sonar,the Doppler effect will occur,so the reverberation characteristics of different transmitted signal interfaces under motion conditions are different from those under stationary conditions.Therefore,it is meaningful to study the characteristics of shallow sea interface reverberation under motion conditions and adopt different reverberation suppression methods for interface reverberation of different transmitted signals.Interfacial reverberation is closely related to interfacial scattering,and the seafloor scattering characteristics of different seabed parameters and sea surface scattering characteristics of different sea states are studied by using the small slope approximation model.The small slope approximation has the advantages of fast operation speed,high precision and wide application angle.Combined with the scattering intensity of seabed and sea surface,and using the element scattering model,a motion transceiver and shallow sea interface reverberation model considering the influence of seabed and sea surface was established.This model considers the situation where the platform has moved forward by a certain distance when receiving the echo when the platform moves at a large speed.The time-domain frequency domain characteristics,instantaneous value and envelope value statistical characteristics,time-dependent radius and spatially dependent characteristics of the reverberation signal were analyzed.Different reverberation suppression methods were studied for different transmitted signal forms.Based on the space-time distribution characteristics of CW reverberation,space-time adaptive processing(STAP)was used to suppress CW reverberation,and the advantages and disadvantages of using space-time adaptive processing to suppress shallow sea short-range interface reverberation were analyzed.According to the good focusing of the LFM signal in the fractional order,the fractional Fourier transform(FRFT)is used to suppress the LFM reverberation.Variational mode decomposition was used to suppress CW reverberation,LFM reverberation and BPSK(phase coding)reverberation,and the results of variational mode decomposition(VMD)processing of different transmitted signal reverberations were compared.Combined with the experimental data,the rationality of the reverberation model and the effectiveness of fractional Fourier transform suppression of LFM reverberation and variational mode decomposition suppression of reverberation are verified.