Research On Extraction Approach Of Elastic Scattering Of Underwater Target Based On Wavelet Transform

Underwater target detection and recognition has been the major issue in the field of underwater acoustic research field.The key of this issue is to extract the information of physical properties and characteristics associated with the target itself.In general,the target feature is a direct result of the target echo obtained from time domain,frequency domain or time-frequency domain signal processing approach,but for the target echo both bearing the geometrical scattering echo and the elastic scattering echo,aliasing are present both in the time domain and frequency domain,the existing signal processing approach can not obtain the elastic scattering highlights' information directly from the frequency or time domain limited by the resolution issue.According to research results,the elastic highlights exist in a certain angle range and a certain frequency range,and also the elastic highlights in the echo frequency spectrum exist in the form of interference in local spectrum.Therefore,this paper presents an approach considering the spectrum of target echo signal as a kind of time-domain signal,using wavelet transform to extract the elastic highlights interference spectrum,providing new research ideas and solutions.Wavelet transform could use the differences between geometrical highlights interference spectrum and elastic highlights interference spectrum by projecting the target echo spectrum into different signal analysis spaces,so as to obtain a certain space in which the geometrical highlights interference spectrum could be weaken and the elastic highlights interference spectrum could be enhanced.This paper simulates the target echo signal from different incident angles based on the sonar target echo highlights model and the method of middle frequency enhancement effect of the elastic scattering of the target and the method of surface surrounding wave circum-ambulation theory.Then the simulated elastic highlights interference spectrum was extracted from the simulated target echo spectrum using frequency continuous wavelet transform and frequency discrete wavelet transform.The simulation results show that frequency continuous wavelet transform could extract elastic highlights interference spectrum in a specific scale,while frequency discrete wavelet transform could extract the elastic highlights interference spectrum in the second and third layer of approximate coefficient reconstruction space.The data of an experiment of measuring a suspension target's acoustic scattering in the anechoic pool is processed in this paper.The processing results show that both frequency continuous wavelet transform and frequency discrete wavelet transform could extract calathiform interference fringes of the elastic highlights in the angle-frequency spectrum corresponding to the theoretical research.The result shows the effectiveness of the approach presented in this paper.