Research On Enhancement And Line Spectrum Recognition Technology Of Radiated Noise Signal Of Underwater Acoustic Target

Underwater acoustic target radiated noise signal is an important information source for passive sonar system to identify underwater targets.With the improvement of underwater target’s ability of damping and noise reduction,the signal intensity of underwater acoustic target’s radiated noise decreases continuously,which makes the passive sonar detection and recognition of underwater target become more and more difficult.The long-distance detection and identification requirements of passive sonar system greatly promote the development of hydrophone towed array towards large aperture.However,the large aperture towed linear array is faced with two outstanding problems in the application of target detection and recognition: formation distortion and strong interference of multiple targets.In view of these two outstanding problems in the practical application of large aperture towed array,research on underwater acoustic target radiated noise feature enhancement and line spectrum identification technology is carried out.The main work contents and innovations are as follows:1.A method of enhancing radiated noise signal of underwater acoustic target based on distortion condition is studied.In order to solve the formation distortion problem of large aperture towed array in practical application,a data-driven towed array shape estimation method is proposed.Firstly,the amplitude and phase information of the strong line spectrum were extracted by using the line spectrum detection method,and the nonlinear filtering technique of singular value suppression was proposed to obtain the high-precision delay estimation.Based on the estimated delay estimation,the distortion formation information was obtained in real time,so as to enhance the radiated noise signal of underwater acoustic target under the condition of distorted towed array.Experimental results show that the average gain of the line spectrum of the tracking beam proposed in this paper is about 2.9d B.2.A line spectrum identification method based on multi-target strong interference underwater acoustic environment is studied.In order to solve the problem that the line spectrum features extracted from multi-target underwater acoustic environment have strong interference line spectrum,a line spectrum identification method based on strong line spectrum sparse estimation of arrival direction was proposed from the perspective of frequency domain.Firstly,the high resolution azimuth estimation is obtained by using compressed sensing technology.Then,the matrix data of azimuth history graph of each line spectrum is reduced by principal component analysis method to obtain its low dimensional characteristics.Finally,the k-means algorithm is used to realize the clustering of different azimuth spectrum to realize the identification of weak target line spectrum.Experimental results show that the clustering accuracy of weak target line spectrum is more than 90%.3.A line spectrum purification method based on multi-target strong interference is studied.In order to solve the problem of line spectrum interference in the weak target features extracted from multiple targets with strong interference,a line spectrum purification method based on inverse beamforming interference elimination was proposed from the time domain perspective.Firstly,the time domain waveform of each strong interference source signal is estimated from the array element domain data,then the strong interference source signal is removed from the array element data,and the weak target characteristic line spectrum is purified.The experimental results show that the average gain of line spectrum purification method proposed in this paper is about 2.8d B,and the recognition accuracy of line spectrum is about 83%.