Research On Passive Location Of Interference Spectrum Analysis

Passive detection and location in underwater acoustic has always been the focus of researchers. The passive ranging technology of three elements array is a mature technology. As the further research on the underwater acoustic field, the matched field passive source location is proposed. While TMA (target motion analysis) make full use of the data during a time period to estimate the target moving state. They two are the new hot in passive location field. From the notion of theses two technology, this dissertation explores the new way for passive source location used in single (vector) hydrophone through the analysis on modeling of the acoustic vector field.The research work of the dissertation includes the following three parts: l)analysis on the interference acoustic vector field at low frequency 2)target motion analysis based on the STFT-Hough transform 3)passive location based on the interference period of spectrum.The model of acoustic vector field at low frequency based on the ray theory is made first. Then the transmission loss curve of ray theory and mode theory is compared, which shows that the ray model is a good approximation to the mode theory in near distance. And the interference phenomenon of press and velocity is also discussed. Based on the analysis of the acoustic interference phenomenon, that the interference pattern is hyperbola cluster is deduced. The target motion state will determine the shape of these hyperbola clusters. The difference affect of target traveling in shallow water and deep water to the interference pattern is discussed. Hough transform is a usual method for the image edge detection. It has been used in the underwater acoustic field for estimation combined with time-frequency analysis, exemplified by estimate the frequency slope of the LFM signal with wigner-Hough transform. This dissertation uses the Hough transform to distill the parameter of the hyperbola curve to estimate the target state (speed, depth and the nearest distance).Finally, this dissertation analyzes the relationship between the interference period of the spectrum and cepstrum estimator. The interference spectrum can be used to eliminate the wake effect of the moving target and the strong instantaneous narrowband disturb which could have some application in the short distance detection.