Research On Reverberation Characteristics Of Ocean Waveguide Under Platform Movement

Reverberation is formed by the superposition of the scattered echoes of the transmitted signal by the scatterer,and is one of the main interferences of active sonar.In order to improve the working performance of active sonar,it is necessary to carry out anti-reverberation design for sonar.Bottom reverberation is one of the important sources of reverberation,especially in shallow waters.Platform motion will bring about Doppler effect,resulting in spectrum broadening of reverberation signal.Therefore,it is necessary to study the characteristics of seabed reverberation under the condition of moving platform and find a method to reduce the reverberation interference.Firstly,the bottom scattering model is established according to the small slope approximation method.Compared with the perturbation approximation and Kirchhoff approximation models,the small slope approximation model has the advantages of high calculation accuracy and wide application range of angles.The influence of seabed parameters on backscattering intensity was studied,and the distribution of scattering intensity with seabed topography was studied in combination with three-dimensional seafloor topography.Then,based on the unit scattering theory,the seabed reverberation signal model of the moving platform is established,and the seabed reverberation signal is analyzed from the perspective of the instantaneous value distribution,envelope value distribution,phase distribution,time-correlated characteristics and space-related characteristics of reverberation,and the research on the spatial-temporal distribution of reverberation under motion conditions provides ideas for reverberation suppression.Finally,a reverberation suppression method based on space-time adaptation is studied.The training samples are used to estimate the space-time distribution characteristics of the reverberation,and then the filter weighting coefficients are calculated to suppress the reverberation.The sparse recovery theory is applied to the reverberation space-time power spectrum estimation,which improves the resolution of the space-time power spectrum and enhances the reverberation suppression ability under the condition of small training samples.