Research On Characteristic Of Interference Fringe Of Active Sonar Target In Ocean Channel

Active sonar works in a complex ocean environment.Many factors such as multi-path,sea depth,sound velocity gradient,temperature,etc.will affect the scattering sound field of targets in the water,especially the appearance of stealth targets and various small targets,resulting in weak target characteristics and difficult to extract The inherent characteristics of stable and reliable targets that are conducive to identification.Faced with this problem,this thesis focuses on the sound field changes when there are targets and when there are no targets in the ocean channel.From the three aspects of theoretical simulation,feature extraction,and experimental data acquisition and analysis,it studies the environmental sound field of the ocean channel and the sound field generated by the active sonar target scattering sound field.The interference fringe feature provides an effective way for target detection and recognition.First,based on the normal wave model of underwater acoustic propagation and the theory of environmental sound field waveguide invariants,a theoretical model of the interference fringe characteristics of the active sonar target in the ocean channel is established,and the interference fringes of the ambient sound field when there is no target are obtained through simulation,as well as the conditions for receiving and transmitting together.The interference fringes of the active sonar target under separate conditions are analyzed.The influence of parameters such as frequency and distance,the existence of the target,the deployment method of the active sonar device,and the change trajectory of the target position on the interference fringes is analyzed.Secondly,in order to quantitatively or qualitatively characterize the interference fringe characteristics of the sound field,research on feature extraction methods is carried out.The straight line detection method based on Hough transform extracts the interference fringe characteristics of the marine environment sound field,that is,the value of waveguide invariant,and analyzes the distribution of waveguide invariants in different depth scenarios;proposes a statistical distribution-based interference fringe feature extraction method,The statistical distribution characteristics of the interference fringes of the active sonar target are extracted;the interference fringe feature extraction method based on the curvature sum is proposed,which characterizes the curvature characteristics of the curved fringes generated by the active sonar target.Finally,a lake experiment was carried out at the Moganshan Hydroacoustic Test Site,and the marine environmental sound field data when there is no target and the scattered sound field data when there is a target were obtained.Through data processing and analysis,the sound field interference fringes were obtained,and their waveguides were extracted respectively.The invariant value,statistical distribution feature and curvature feature verify the corresponding theoretical model and feature extraction method.