Research On Near-field Localization Method Of Underwater Target Noise Sources

The radiated noise of underwater targets such as submarines and torpedoes can bedetected and tracked by the passive sonar.Reducing the underwater targets’ radiated noise isan important method to improve its acoustic stealth and tactical indexes.Improving thetechnology to locate underwater targets’ noise,get the distribution and contribution of eachnoise source,which can better guid the noise-reduction,vibration-isolation and acousticdesign,is the most effectively method.Based on the conventional beamforming,this dissertation firstly introduces themeasurement model and principle of the near-filed focused beamforming for the level lineararray.The calculation formula of the focused spatial resolution is deduced.The effect of arrayaperture,frequency and distance from targets on the focused spatial resolution is analyzed.The narrow band near-filed location methods of underwater targets’ noise sources arestudied in this dissertation.Based on level linear array measurement model,the mathematicalmodel of near-filed narrowband signal is given.MVDR,MVDR with amplitude compensationfocused beamforming and Signal Phase Matched Principle is studied after that.And twonear-filed high-resolution methods based on Signal Phase Matched Principle,which isproposed in recent years,are presented in this dissertation.Furthermore,the spatial spectrumcharacter and the focused spatial resolution of these methods are analyzed.The results ofsimulation have demonstrated the high-resolution methods,which are better than conventionalbeamforming method,can implement the positioning of near-filed noise sources.Among thosemethods,ac-MVDR,which has better performance,can get both the spatial distribution andcontribution.Because of single linear array can’t distinguish the starboard and larboard,alsothe spatial resolution is extremely low when the source is at the end-fire direction,the crossedarray location methods is presented and compared with the performance of level linear array.The broadband near-filed location methods are proposed.Sub-band decompositionfocused beamforming algorithm and Signal Phase Matched Principle high-resolution methodfor the non-coherent broadband signals,focused beamforming algorithm based on focusedtransformation for the coherent broadband signals are studied.The spatial spectrumcharacter,the focused spatial resolution and the ability to get the distribution and contributionof these methods are analyzed and compared through the simulation.This dissertation carries out the anechoic tank experiment for the underwater targets’noise sources near-filed location methods and proves the availability of these methods which are studied.The experiment results and theoretical analysis is consistent,which provides theexperimental foundation and guidance significance for engineering application.