Research On High Fidelity Array Processing Technology Of Underwater Acoustic Target Signal

The ship's radiation noise can reflect the related information of the propeller speed,the composition of the power system and the way of the target navigation,which can be used to estimate the parameters of the underwater target,to detect and track the target.However,due to the complexity of the marine environment,when the radiation noise is transmitted in a complex time-frequency and random ocean channel,the useful signals are often distorted and delayed,and are inundated in the background noise,which is very difficult and challenging to detect the ship's radiant noise.Aiming at the signal distortion problem of ship radiated noise in large aperture array receiving,this paper develops a high fidelity array processing technology for underwater acoustic target signals.In this paper,the cause of the signal distortion in the large aperture array processing is analyzed.A high fidelity beamforming method is proposed and the design of the high fidelity array processing system is completed.The main research work of this paper is as follows:1.The purpose of array signal processing is to obtain higher signal to noise ratio.The remote field propagation model mismatch,the amplitude or phase weighted inconsistency of the array element,the estimation error of the target azimuth and the array distortion and so on directly affect the performance of the array processing.In this paper,the effect of target azimuth estimation error on high fidelity signal recovery is analyzed in detail,the spherical wave propagation model of the near field target is discussed,the delay error generated by the plane wave hypothesis is deduced,and the amplitude and phase error model of the array is introduced,and the correspondence between the amplitude weighted inconsistencies and the phase weighted inconsistencies of the multiarray elements is analyzed.The array shape distortion caused by the platform maneuver is studied.The arc model and the sinusoidal model are established,and the influence of the towed array distortion on the high fidelity array signal processing is analyzed,and the influence of the strong interference factors on the target tracking and the extraction of the characteristic parameters in the background environment is studied.2.Aiming at the problem of target characteristic distortion caused by frequency dispersion,a constant beam width beamforming method based on DFT interpolation is studied.In order to further improve the working frequency range of the constant beam width beamformer,the continuous linear array model is introduced into the actual linear array,and a nonuniform array design method with frequency invariant characteristics is derived,and a broadband beamformer with frequency invariant characteristics is realized,which can obtain high fidelity target in a wide frequency range.3.Aiming at the problem of target characteristic distortion caused by large aperture array distortion,an array calibration method based on strong line spectrum azimuth vector estimation is proposed.This method searches the optimal direction vector by the narrow band strong line spectrum,and converts the direction vector to the time delay of wide band array.Because of the accurate delay compensation,the beamformer based on this method will have better signal fidelity.The selection criteria of strong line spectrum and the method of phase continuity processing between adjacent array elements are studied.The effectiveness and practicability of the algorithm are verified by simulation experiments and real sea trial data experiments.4.A design scheme of high fidelity beamforming real-time processing system based on multi-core DSP is proposed.The combined adaptive generalized sidelobe cancellation technique,strong line spectrum azimuth vector estimation and constant beam width technique effectively suppress the effect of strong interference,towed array distortion and frequency dispersion on target characteristics,and obtain high fidelity targets.