Research On Analytical And Numerical Methods Of Electromagnetic Scattering From Randomly Rough Surfaces And Vegetations

The Electromagnetic scattering from randomly rough surfaces and vegetations have been attracting wide interest of researchers, thanks to their significant application in the spheres of meteorology, oceanography, environment, military and so on. This dissertation made intensive research on Electromagnetic scattering from randomly rough surfaces and vegetations from the two aspects of analytical theory and numerical simulation.In terms of scattering from randomly rough surfaces, this paper carefully treated statistical distribution of slope or normal vector of surface, which were oversimplified by former analytical models; proposed a statistical slope Kirchhoff model for lossy dielectric rough surfaces, hence fully taking into account two sets of statistical property, that is, height and slope. The proposed model introduced joint probability density function of surface normals to characterize their random distribution; furthermore, to simplify multiple fold integral involved in calculating ensemble averaging of scattering amplitudes, a decomposition scheme of slope covariance matrix was presented, which contained explicit physical meaning relating to correlation of slopes, and made possible the entire theory deduction and final simple analytical formulae for scattering coefficient computation..For numerical simulation of rough surfaces, the problems of slow convergence and large memory requirement exited for the sparse matrix canonical grids method proposed by Tsang, for quite rough surfaces, were briefly discussed; Also, this method was implemented by Fortran programming language, as to validate analytical models and construct simulation platform for solving convergence problem and further intensive and deep researching on numerical simulation.In the field of electromagnetic scattering from vegetation, this dissertation made research on backscattering from the soybean, a typical species of short vegetation, and presented a model incorporating the benefits of branch model and Phase and Amplitude Correction Theory. In modeling inter-plant structure, the model introduced an antenna theory to take into consideration the quasi-periodic characteristics common in agricultural planting practice. Moreover, this proposed statistical slope Kirchhoff model was adopted for direct scattering contribution of only randomly rough surfaces instead of traditional Kirchhoff approximation or small perturbation method; and in terms of the ground-scatter bounce scattering, conventionally used Fresnel reflection coefficient was modified to make full consideration of the impact of roughness of underlying surfaces. Finally, comparisons of model predictions with measuremental results validated this proposed model.