Electromagnetic scattering from periodically loaded cylinders

Summary form only given. The plane wave scattering from perfectly conducting periodically loaded or corrugated cylinders at skew incidence can be analyzed by several methods, according to the geometrical and material properties of the scatterer. Two basic configurations recur in practical applications, with the corrugations or loading; either along the z axis of the cylinder or in the transverse plane. This latter case can be solved by exploiting the periodicity of the structure along the cylinder axis. Since the scatterer is a periodic function of z with period d, the fields observed at two arbitrary points, separated by a distance d along a line parallel to the z-axis, are identical except for a constant phase shift. This means that it is necessary to determine the fields only in a basic cell of the periodic cylindrical structure, which is enclosed by the planes z=/spl plusmn/d/2. In this paper, different methods for the analysis of the problem are discussed and compared, both in the cases of longitudinal and transverse loadings. Particular attention is devoted to the case of transverse corrugations or loadings. In this context, a special formulation of the method of moments is applied, which utilizes a periodical free-space Green´s function. When the cylinder cross section is circular, typical Floquet´s modal expansions are also considered. Finally, in the presence of more complex configurations a hybrid technique is used, which combines the finite element method (FEM) with the Floquet´s expansion.