Study On The Algorithm Of Weak Target Detection On Sea Surface Based On Shore-based Radar

The sea clutter formed by the backscattering of the oceanic surface interferes with the radar detection of targets seriously,the weak targets on the oceanic surface are often drowned out by sea clutter.In order to improve the ability of weak targets detection on the sea surface by radar,this thesis analyzes the characteristics of sea clutter based on the X-band measured sea clutter data of a shore-based radar,and studies the weak targets detection algorithm on the oceanic surface.The main research work of this paper is as follows:In the first part,the characteristics of sea clutter,including physical scattering characteristics,statistical characteristics,time-frequency characteristics and spatiotemporal correlation,are analyzed by using measured sea clutter data.Firstly,by analyzing the causes of sea clutter,the conclusion is drawn that the physical scattering model of sea clutter is composed of one or more scattering models of Bragg scattering,burst scattering and whitecap scattering.Then,the statistical characteristics of sea clutter are analyzed by using four typical statistical characteristics models of sea clutter,through the probability density function(PDF)fitting of strong and weak sea clutter data,it is concluded that the strong and weak sea clutter conform to different distribution.The time-frequency characteristics of strong and weak sea clutter in the measured sea clutter data are analyzed by using the short-time Fourier transform(STFT)and Wigner ville distribution(WVD),and a solution to suppress the cross term of WVD is provided.Finally,the temporal and spatial correlation of sea clutter is studied by analyzing the temporal and spatial correlation of strong and weak sea clutter in the measured sea clutter data.In the second part,the traditional singularity value decomposition(SVD)algorithm for sea clutter has the problems of high algorithm complexity and high false alarm rate.Based on the characteristics that the energy of sea clutter in the same range cell is much higher than the target,an improved SVD algorithm for sea weak target detection is proposed.This algorithm can realize the detection of weak targets on the sea surface with a low algorithm complexity.It does not require the prior information of the target and sea clutter.It can detect moving and stationary targets at the same time.However,there are limitations in the scope of application and the problem that the target and sea clutter are suppressed at the same time.In the case of multiple targets in the same resolution unit,the detection effect is not good,and it is suitable for data with more sampling points.In the third part,according to the difference of Doppler frequency stability between target and sea clutter in time-frequency domain,an algorithm of weak target detection based on short-time Fourier transform(STFT)is presented.The algorithm can detect weak targets on the sea surface.It can detect moving targets and stationary targets at the same time.It does not require prior information about the target and sea clutter.It can detect multiple targets with large differences in signal-to-clutter-to-noise ratio in the same resolution unit.The algorithm has no false alarm problem.Using WVD has good time-frequency aggregation,the weak target detection algorithm based on short-time Fourier transform is improved to retain its advantage in dealing with the same resolution unit where there are multiple targets with large difference in signal-to-clutter-to-noise ratio,a weak target detection algorithm based on STFT and WVD is presented.Compared with the weak target detection algorithm based on STFT,this algorithm can detect targets with lower signal-to-clutter-to-noise ratio.In order to further detect targets with lower signal-to-clutter-to-noise ratio,the constant false alarm(CFAR)detection in frequency domain is introduced to improve the weak target detection algorithm based on STFT and WVD,and the STFT and WVD based on statistics are presented.Compared with the weak target detection algorithm based on STFT and WVD,the proposed algorithm can detect targets with lower signal-to-clutter-to-noise ratio,and has a good detection effect for multiple targets with the same resolution unit.