Study On The Modeling Of Underwater Acoustic Countermeasure Equipments And The Methods Of Target Feature Extraction

Underwater acoustic countermeasure is a key technology of underwater electronic warfare. The Underwater acoustic countermeasure experiments are an important part in the research of underwater acoustic countermeasure. The underwater acoustic countermeasure experimental simulation and evaluation system is an efficient tool that is used mostly for the mathematical and multimedia simulation of the underwater acoustic countermeasure experiments, the evaluation and analysis of the experiments. Based on the general study of underwater acoustic countermeasure technology and underwater acoustic countermeasure equipments, this thesis mainly studies the modeling of the underwater acoustic countermeasure equipments, which includes mathematical modeling and simulation modeling. These studies provide the foundation for the underwater acoustic countermeasure experimental simulation and evaluation system. The thesis is also concerned with the feature parameter extraction methods of the underwater targets to improve the countermeasure ability of the equipments, which keeps track of the development of underwater acoustic countermeasure technology. Main results of the thesis are summarized as follows:1. Based on the analysis and study of the primary principle and countermeasure process of the underwater acoustic countermeasure equipments, The mathematical models of the typical underwater acoustic countermeasure equipments such as the wide-band noise jammer target radiation noise simulator echo simulator and the gas bubble are presented. The validity of the models is also given based on the computer simulations, and models verified by using the sampling data of real underwater targets.2. The performance of several real underwater acoustic countermeasure equipments like the noise jammer, the acoustic bait and the gas bubble are investigated. The mathematical models and simulation models are built up based on the function parameters and work principle of these underwater acoustic countermeasure equipments. The computer simulations show the validity of the models.3. Joint estimation of the time delay and Doppler frequency based on short-time Fourier transform(STFT) and time-frequency analysis are studied to estimate the parameters of the underwater target echo. The statistical performance of the joint estimation method is discussed based on the simulation, and the results show the good performance of the method at low SNR.4. The feature parameter extraction methods of the underwater target are studied which can improve the performance of the underwater acoustic countermeasure equipments. Several feature extraction methods such as the scale invariance feature extraction , target pole extraction Fourier - Mellin Transform etc are investigated by computer simulations. The experimental results demonstrated the efficiency of these feature extraction methods in the applications of underwater target recognition.