abstract: Scattering from random rough surface has been of interest for decades. Several methods were proposed to solve this problem, and Kirchho approximation (KA) and small perturbation method (SMP) are among the most popular. Both methods provide accurate results on rst order scattering, and the range of validity is limited and cross-polarization scattering coecient is zero for these two methods unless these two methods are carried out for higher orders. Furthermore, it is complicated for higher order formulation and multiple scattering and shadowing are neglected in these classic methods. Extension of these two methods has been made in order to x these problems. However, it is usually complicated and problem specic. While small slope approximation is one of the most widely used methods to bridge KA and SMP, it is not easy to implement in a general form. Two scale model can be employed to solve scattering problems for a tilted perturbation plane, the range of validity is limited. A new model is proposed in this thesis to deal with cross-polarization scattering phenomenon on perfect electric conducting random surfaces. Integral equation is adopted in this model. While integral equation method is often combined with numerical method to solve the scattering coecient, the proposed model solves the integral equation iteratively by analytic approximation. We utilize some approximations on the randomness of the surface, and obtain an explicit expression. It is shown that this expression achieves agreement with SMP method in second order. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2017

[pt] O presente trabalho estuda a interação entre objetos condutores perfeitos tridimensionais, de formas arbitrárias e campos eletromagnéticos harmônicos no tempo incidentes sobre os mesmos. Pretende-se determinar os campos espalhados pelos objetos, caracterizados por uma malha de elementos de contorno planos e triangulares. Através de um tratamento numérico aproximado da Equação Integral do Campo Magnético, a densidade de corrente induzida na superfície do condutor perfeito é obtida. De posse deste resultado, determina-se o campo magnético espalhado (campo distante) e calcula-se a seção reta radar em várias direções. As vantagens e desvantagens da utilização do Método dos Momentos serão apontadas. Os resultados obtidos pelos mesmos serão comparados entre si e com aqueles disponíveis na literatura. / [en] This work studies the interaction between tridimensional perfect conducting objects of arbitrary shapes and incident time-harmonic electromagnetic fields. The fields, scattered by these objects, are determined using a finite number of plane and triangular boundary elements. The induced current density on the boundary is obtained using the Magnetic Field Integral Equation, applied approximately in a numerical approach. With the result mentioned above, the scattered magnetic field (far-field) is determined and the Radar Cross Section is calculated. The advantages and disadvantages of the use of a numerical method (moment method) are pointed out and the results compared. With those in literature.