Application Of Volumetric Perturbation Method For Scattering From Rough Multilayers

The existence of oil film on the sea surface has important influence electromagnetic scattering of sea. Especially in the case of high frequency, the thickness of oil film cannot be ignored and the properties of oil should be taken into consideration, or a decline in the performance of radar detection will be caused. There are lots of such multilayered structures, so studying its scattering mechanism and characteristics is of great importance. Perturbation methods are often used in inhomogeneous stratifications, and Volumetric Perturbation Method is one of them. In this paper we present the Volumetric Perturbative Reciprocal Theory, the derivation process of the scattering solutions and how to solve the problem of scattering from multilayered structures in detail. The main work is as follows:1. This paper introduces the basic principle and knowledge of rough surface, the method of geometry modeling such as linear filtering method. Finally, the numerical results and discussions of Gaussian and PM surfaces are given by linear filtering method.2. This paper introduces the formulation of volumetric perturbation method. Then the first order and second order perturbation scattering solutions are derived to calculate the electromagnetic scattering from single rough surface. We focus on the two essential quantities,the zeroth order field and perturbation of relative dielectric permittivity. Through to the appropriate definitions and assumptions of the model, the perturbation of relative dielectric permittivity is deduced with corresponding mathematical theory. The zeroth order field is obtained by propagation equations, the Fresnel reflection and transmission coefficients and so on. Finally the bistatic scattering coefficients of a single rough surface are given and some numerical results are simulated and discussed.3. In the case of multilayered structure, perturbation of relative dielectric permittivity and the zeroth order field can be similarly obtained by Fresnel reflection and transmission coefficients, transmission matrix and generalized propagation coefficients. Based on the formulation of volumetric perturbation method, the first-order scattering solutions are presented. Then we calculate the electromagnetic scattering from multilayered rough surfaces and give a comparison with MOM.4. Considering the existence of oil film on the sea surface, the sea surface capillary wave will produce a damping effect. The original model cannot meet our requirements. This paper uses the modified PM spectrum simulating the one dimensional layered model of insoluble oil and sea. Through the comparison of scattering coefficients, the validity of using modified PM spectrum is proven.