A Study On Matched Field Processing Of Underwater Acoustic Signals

This dissertation studies mainly the inversion of ocean environmental parameters by MFP (Matched Field Processing). Meanwhile, adaptive matched field passive localization in complex environment and discrete noise rejection with MFP are discussed. The main contributions are as follows:(1) DE (Differential Evolution) algorithm is proposed to invert the ocean acoustic parameters in shallow water in order to get faster and more accurate results than GA (Genetic algorithm) and SA (Simulated Annealing algorithm). Also a posteriori probability analysis method is applied to evaluate the uncertainty of inversion results.(2) Maximum likelihood objective functions for broadband MFI are derived according to different conditions. Meanwhile, coherent and non-coherent broadband MFP is studied. After analyzing the sensitivity of different inversion parameters, a new approach named MS-MFI (Multi-step MFI) is proposed for inversion in order to improve the efficiency.(3) Applying MS-MFI, ASIAEX2001 (Asian Seas International Acoustic Experiments) data are used to invert environmental parameters in the East China Sea. According to the different ocean environment, range dependent and range independent inversion are studied and the inversion results are analyzed.(4) In order to reduce the snapshots needed by passive localization in complex ocean environment, reduced rank AMFP frame is founded and many algorithms are compared. In mismatch environment, two robust AMFP algorithms are compared. Meanwhile, motion compensation method is used for AMFP to improve the localization effect. With strong interferes at surface, non-stationary noise field and mismatch environment, subspace motion compensation method and efficient AMFP system frame are proposed and confirmed by simulation and real data.(5) MFPIC (Matched Field Postbeamformer Interference Canceller) is proposed to cancel tow ship's noise. The advantage of MFPIC is that it can be used to cancel the tow ship's noise for all arrival directions. Furthermore, this new approach can be used to detect weak target, which has the same bearing angle of a strong interference. Numerical results show that the MFPIC outperforms the conventional PIC. MFP-PIC (Matched Field Processing with Postbeamformer Interference Canceller) is also proposed to cancel strong interference and detect the underwater weak target.