Research On Weak Target Detection Under Sea Clutter Background

Radar strong sea clutter and multipath interference will seriously affect the detection performance of low-altitude targets on the sea surface.Strong sea clutter will submerge weak target signals,and multipath interference will seriously affect the stability of detection.The characteristics and modeling methods of sea clutter and the influence of multipath effect of radar low-altitude targets are analyzed in this paper.In order to effectively improve the detection performance of low-altitude weak targets in sea clutter background,methods of sea clutter suppression and multipath suppression are proposed.The effectiveness of these methods is verified by the measured data and simulation analysis.The specific work of this paper is as follows:1.The characteristics of sea surface and wave are described.The empirical models of NRCS of sea clutter are introduced and analyzed.The statistical models of sea clutter amplitude and the methods of parameter estimation are introduced,and the amplitude characteristics of the measured sea clutter data are analyzed.The characteristics of the measured sea clutter spectrum are analyzed,and a Doppler spectrum modeling method of sea clutter which can change with time is given.2.A sea clutter suppression method based on short-term nonlinear prediction is proposed.NGD algorithm based on feedforward nonlinear filter and CRTRL algorithm with feedback filter are presented.The sea clutter suppression method of nonlinear prediction is validated and analyzed by using measured sea clutter data.The performance of the proposed sea clutter suppression method is compared with that of linear filter.3.A method of sea clutter suppression based on Radon transform and wave parameter inversion is proposed.The principle of Radon transform and its inverse transform are introduced.The dispersion equation of gravity wave is given.The process and principle of wave spectrum and parameter inversion are described in detail.The process of this sea clutter suppression method is given.Finally,the method is validated and analyzed by the measured sea clutter images.4.A low altitude target detection method based on generalized likelihood ratio of frequency diversity radar is proposed.The reflection coefficient of sea surface and the influence of multipath effect are analyzed,the echo model of low-altitude target of frequency diversity radar is established,and the detection method of low-altitude target with generalized likelihood ratio is proposed.This method is analyzed and compared with several low altitude target detection methods of radar,the effectiveness of this method is verified by computer simulation.In this thesis,the problem of low-altitude weak target detection in sea clutter is considered.The data-level and image-level sea clutter suppression methods are discussed respectively,and the strong sea clutter interference is suppressed from multiple perspectives.The generalized likelihood ratio detection method based on frequency diversity is proposed to suppress the multipath effect and effectively improve the performance of target detection.