Research Of Modulation Feature Extraction From Ship-radiated Noise

Information degree of the future naval battle will be very highly, and Striving for information advantage is the foundation of winning modern naval battle. Accurate and prompt recognition is the premise and foundation of tactical command. Modern naval battle is fast and complicated, and submarine sonar is required to be able to detect and classify targets fast and precisely .So the passive target detection and identification is the important research part in the modern acoustic technique field.High-Order Statistics (HOS) analysis handles a forward position in domestic and international signal processing realm nearly twenty years. High-order statistics is applied to all problem that need to consider non-gauss non-minphase non-linear and circular calm. So Higher-order statistics is the primary analysis tool in analyzing non-Gaussian signal and nonlinear signal. It has plenty of application in signal detection, feature extraction and parameter estimation. In this paper, the base frequency of the ship is estimated with the application of the HOS.The main research of this thesis focuses on four aspects as following:Firstly, the definition and properties of HOS are introduced; The HOS is insensitive to Gaussian process. This is the theoretical basis of signal detection and estimation. Because of 1(1/2) spectrum having the properties of the higher orderspectrum and relatively small calculation amounts, the property of 1(1/2) spectrumis introduced and the validation of emulation is given.Secondly, the mechanism of ship-radiated noise is analyzed. I build the envelope detection model of the ship noise. Analyzing and comparing three ways of the envelope, the envelope spectrum is extracted through the methods of the HOS. Through the purity of the envelope spectrum and the smoothness of the continuous spectrum, I separate the line spectrum, from which the target base-frequency related with the rotate speed of ship screws can be detected. Lastly, the methods of extracting frequency features of the ship radiated noise envelop are presented by using difference frequency and double frequency method, which is the basis of the classification. Using Matlab's GUI, The software of cover is designed that is composed of all methods and process mentioned in the paper. By which the information of the various kinds of targets can be achieved.