Study Of Electromagnetic And Optical Scattering From Sea Surfaces

In this paper the methods for modeling sea surfaces are outlined, including statistical models and fractal models with emphasis on the extended fractal models, then the conventional two-scale model is modified to calculate the electromagnetic scattering from two-dimensional rough sea surface. The slope of large roughness is obtained numerically. For large incident angle the Z-BUFFER method is applied to calculate the shadowing function and the curvature effect of large roughness is taken into consideration. By contrast with experimental data it can be concluded that the modified two-scale model is effective.The two-dimensional time-varying sea surface is generated and several sets of time series of backscattering coefficient from it for different parameters is obtained with modified two-scale model. Then the chaos theory is applied to analyze sea clutter. The phase space reconstruction technique and calculation of correlation dimension are discussed, and a method for calculating the largest Lyapunov exponent is presented, which places no restriction on the length of time series and is easy to implement.The mutual coherence and angular correlation function of scattered wave from two dimensional rough surfaces is derived with Integral Equation Model and then calculated for perfectly conducting rough surfaces, then the scattering of incident pulse wave with different shape is calculated and the shape of scattered pulse is presented.The mutual coherence and angular correlation function of scattered wave from two dimensional non-Gaussian rough surfaces is deduced using the Gram-Charlie distribution, then the pulse scattering from two dimensional rough sea surface is calculated, and pulse broadeding is discussed.The geometry optics approximation are combined with Kirchhoff approximation and small perturbation method to calculate the optical scattering from rough sea surfaces. The background radiation of the Solar and sky is obtained by Lowtran7, then the scattering of the background radiation of the Solar and sky from Southeast China sea surfaces for different time, frequency and sea state is studied.