Study On The Characteristic Of Electromagnetic Scattering From The Actual Rough Land Surface

In this paper, the fundamental theory of electromagnetic scattering from the rough surfaces is introduced, different methods of electromagnetic scattering from the rough surfaces include the Kirchhoff Approximation, the Small Perturbation Approximation and the Method of Moment are discussed. Based on the comparisons between the Gaussian spectrum rough surface and Exponential spectrum rough surface, the reason of selection the Exponential spectrum rough surface as the actual land surface is given. Wang and Schmugge's Four-elements model which shows the relation between the soil'humidity and the relative permittivity with different types of soil is introduced. Based on the Scalar Approximation and Stationary-Phase Approximation , the electromagnetic scattering in medium 2 under the rough surface is studied and formulae of the transmission coefficient for different polarization is presented with considering the autocorrelation function of the Exponential rough surface. The curve of the scattering coefficient for different polarization transmission wave with varying of the scattering angle, the scattering azimuth angle and the frequency of the incident wave is obtained by numerical implementation, the influence of the dielectric constant, rough surface parameters and the frequency of the incident wave on the transmission coefficient for different polarization transmission wave is discussed, the basic characteristics and the characteristics with varying of frequency of the transmission coefficient from Exponential rough surface is obtained. An analytical method to calculate the bistatic-scattering coefficients of a two-dimensional layered dielectric structure with slightly rough interfaces is presented. The waves in each region are represented as a superposition of an infinite number of up and down going spectral components whose amplitudes are found by simultaneously matching the boundary conditions at both interfaces. A Small Perturbation formulation is used up to the first order, and the scattered fields are derived. The calculation intrinsically takes into account multiple scattering processes between the boundaries. Meanwhile, a current based hybrid method combining the MOM with the Kirchhoff Approximation for analysis of scattering interaction between a two-dimensional infinitely long, conducting of arbitrary cross section and a one-dimensional Exponential rough surface is proposed. The numerical results give the scatterings of composite model with different size and height of target illuminated by a taper wave with different polarized wave for different incident angles. Finally, the numerical results are compared with those obtained by the conventional MOM, and the validity of our hybrid method are verified.