Multiple Parameter Estimation By Joint Methods In Deep Ocean’s Reliable Acoustic Path

As an important research direction in the field of ocean acoustics,underwater target positioning has been attracting the attention of underwater acoustic researchers.With the continuous development of marine science and technology in China,the research object has gradually expanded from the shallow ocean environment of the continental shelf to the deep ocean environment.However,compared with shallow ocean environments,deep ocean environments have significant differences in spatial scales and acoustic propagation characteristics.In this paper,starting from the study of deep ocean acoustic propagation,the emphasis is placed on the study of the acoustic propagation characteristics of deep ocean sound fields,the physical characteristics of sound fields under reliable sound paths,and the basic laws of change.Combining the physical characteristics reflected by the acoustic field with vector acoustic signal processing methods and proposing methods for target parameters such as depth or velocity.The relevant theories and methods have been verified by computer numerical simulations.The main research work of this paper is as follows:1.Studied the characteristics of a reliable acoustic path in the deep sea at large spatial scalesFirstly,this paper introduces the theoretical model of underwater acoustic propagation in a waveguide environment and expounds the basic laws of underwater acoustic propagation.Using the normal mode model and the ray theory model to model and simulate the reliable acoustic path in deep ocean and analyze the advantages of the reliable acoustic path.The influence of sound velocity gradient distribution on reliable sound paths is studied and verified by numerical simulation.2.Researched a method for source depth estimation in the deep ocean using a single vector sensorA method for estimating the depth of a target using a single vector hydrophone is researched based on the multipath arrival structure of the received sound field during the propagation of sound waves generated by targets near the sea surface through reliable sound paths.At medium to close distances,sound waves propagating through reliable acoustic paths are received below critical depths,and the main contributions to the sound field are direct waves and surfacereflected waves from the sea surface.The vector acoustic field composed of direct and surfacereflected waves that are received by a single vector hydrophone is described by ray theory.The expression of the periodic interference structure of sound pressure and particle velocity is derived based on the characteristics of the moving state of the target.Studied the relationship between the periodic interference structure of sound pressure and particle velocity,target vertical arrival angle,and target depth.The target depth information contained in periodic interference structures is estimated using the transform method and the zero-point characteristics of periodic interference structures.In addition,the horizontal distance of the target is further estimated using the relationship between the target depth,target vertical arrival angle,and horizontal distance.Finally,numerical simulation verifies the effectiveness of the proposed target depth estimation method.3.Researched a multi-parameter joint source estimation method based on a vector vertical arrayBroadband target signals have more abundant information,allowing the received acoustic field to reflect more physical parameter information about the target.The acoustic field generated by a broadband target has an interference fringe structure related to the depth of the target,and there is a close relationship between the interference fringe and the depth of the target.Therefore,based on the characteristics of receiving broadband signals with a vector vertical array combined with broadband beamforming methods,a depth estimation method for broadband targets is researched.The acoustic field generated by a moving target exhibits velocity-dependent interference fringes at the depth of the receiver.Using the sound pressure and vibration velocity information received by any element of the vector vertical array,one can construct a cross correlation velocity fringe,and the radial velocity of the target is estimated using the Fourier transform.Numerical simulation verifies the effectiveness of the multiparameter joint estimation method for broadband source based on vector vertical array.