Line Spectrum Identification Based On Spatiotemporal Flutuation Characteristics

The line spectrum of the radiated noise of underwater acoustic targets is an important object for modern sonar equipments to detect and capture.Affected by factors such as the correlation between the effective aperture of the array and the target orientation,strong low-frequency interference in the marine environment,and array distortion,multiple targets received by the array often interfere with each other,which seriously affects the performance of target detection and recognition.This paper mainly discusses the line spectrum identification method based on the spatiotemporal fluctuation characteristics.The effectiveness of the line spectrum identification method is verified through the processing of simulation data and sea trial data.The main research contents are as follows:1.Through the research on the generation mechanism of ship radiated noise,and the extraction of radiated noise line spectrum based on time-frequency analysis theory and generalized likelihood ratio,the stability of ship radiated noise line spectrum in frequency and amplitude is analyzed.2.A sparsity-driven line enhancement algorithm based on LMK(Least Mean Kurtosis)is proposed.This algorithm uses the negative kurtosis of the error signal as a cost function,and adds a zero-attracting term in the frequency domain weight vector correction formula to reduce the amount of offset,thereby suppressing the noise component in the signal.The simulation results found that the line spectrum gain of ZA-ALE based on LMK is improved by about 0.6d B compared with conventional ALE.The processing of sea trial data also verifies that the performance of ZA-ALE based on LMK is better.3.A method to identify the depth of the target line spectrum using the target radiated noise line fluctuation index based on the power average function is proposed.By analyzing the depth modulation effect of the ocean on the targets and the influence of the direction finding error caused by the beam forming on the fluctuation of the target line spectrum,the target radiated noise line amplitude fluctuation index model is established.The results of simulation data and sea trial data show that this model can effectively identify the line spectrum.4.A method of identifying the depth of the line spectrum by calculating the modified scintillation index for the mode excitation function is proposed.By studying the mode filtering of the vertical linear array,the mode filtering process of the tilted linear array under certain conditions is deduced on the basis of the vertical linear array.And The effectiveness of this line spectrum identification method is verified through simulation and sea trial data processing.