Research On Electromagnetic Scattering Properties From The Dynamic Sea Surfaces And The Targets

The research on electromagnetic(EM) scattering from the dynamic sea surface is of great theory value and application prospect in many fields such as sea microwave remote sensing, radar target recognizing and precision-guiding, radar early warning and imaging. Real engineering application is very concerned about the problem of how to efficiently simulate the EM scattering characteristics of 2-D time-varying dynamic sea surface. According to the particularity of the dynamic sea surface EM scattering, this paper presents the research on the EM scattering from the sea surface using the numerical methods, approximate methods, and the hybrid method. The main contents are as following.Firstly, according to the results of previous studies analyzed the dynamic sea surface modeling method, we gave some basic definitions of sea modeling and discussed several sea-spectrum models which were commonly used in ocean surface radar scattering studies, provided the necessary theoretical models for the subsequent analysis of EM scattering from the dynamic sea surface.The Integral Equation Fast Fourier Transformation(IE-FFT) has been applied in the scattering analysis of sea surface. In order to deal with the scattering problem of sea surfaces, the tapered-wave was introduced to cut off the sea surfaces, the impedance boundary conditions was also introduced to deal with dielectric sea surfaces. The core idea of IE-FFT is the interpolation of Green’s function, This method was effective in reducing the computation time and memory while maintaining high accuracy. The scattering analysis for the sea surfaces with different parameters were investigated according to IE-FFT. This method can provide requisite reference data for engineering application.The numerical methods cannot solve problems arise in engineering application which requires scattering information of the electrically large sea surface at high frequencies. The application of physical optics(PO) based on the frequency domain integral equation has been applied in the scattering analysis of relatively flat sea surface. Based on the PO, the iterative PO(IPO) was introduced to analyze the EM coupling effects among the elements of complex sea surface. By comparison with the exact numerical results, confirmed that PO and IPO were in a significant reduction in requires of computation time and memory, the sea scattering results of PO and IPO can meet the needs of engineering applications.In order to analyze the composite scattering between sea surface and the above target, the hybrid method has been used. This method combining the advantages of IE-FFT and PO was applied to solve scattering of target and sea surface, respectively, and the iteration process was utilized to analyze the EM coupling effects between them. The scattering coefficient of the sea surface and target composite model has been analyzed.At last, the analysis for the sea clutter amplitude distribution model under different radar system parameters、observation geometry parameters and sea conditions were investigated according to dynamic sea clutter data which based on quasi-static model simulation.