High Frequency Analysis of EM Scattering from a Circular Conducting Cylinder with Dielectric/Ferrite Coating.

摘要

An approximate asymptotic high-frequency solution is obtained for the field exterior to a two-dimensional circular conducting cylinder with a thin dielectric/ferrite coating. The formal integral representation for the field is evaluated asymptotically via the stationary phase method for the field in lit region and via the residue theorem for the field in shadow region. The obtained solution is cast in the format of the geometrical theory of diffraction (GTD). In the lit region, the geometrical optics (GO) solution consists of the direct incident ray and the reflected ray. The ray picture associated with the reflected ray for the coated cylinder remains the same as that for the conducting cylinder without coating. The reflection coefficient for the field reflected at the specular reflection point on the coated circular surface is approximated by the reflection coefficient for a grounded planar dielectric/ferrite slab with a plane wave incidence. In the shadow region, the residue series solution can be interpreted as the usual creeping wave diffraction of the GTD solution with the same ray path as the diffracted field associated with the conducting cylinder without coating. In the transition regions adjacent to the shadow boundaries where the pure ray-optical solution fails, a 'universal' transition integral of the uniform GTD (UTD) is employed to obtain the uniform solution. Numerical data for the essential transition integral is deduced, via a heuristic approach, from the exact eigenfunction solution together with the GTD solutions for the coated cylinder. The solution is convenient for the engineering applications due to its simple ray format. Numerical results obtained from the UTD solution for the cylinder with thin coating show excellent agreement with the exact eigenfunction.