A. Armogida

EM scattering from the edge of a semi-infinite planar strip grating using approximate boundary conditions

Electromagnetic scattering by the edge of a semi-infinite, dense planar grating of free-standing metallic strips is analyzed. The grating is illuminated by an arbitrarily polarized plane wave impinging on its edge at oblique incidence. The strips can be arbitrarily oriented with respect to the edge. An equivalent canonical problem is defined by adopting for the strip grating well-known approximate boundary conditions derived in the framework of homogenization techniques. The exact spectral solution for the above canonical problem is deduced by the application of the Sommerfeld-Maliuzhinets method, and explicitly depends on the grating parameters. The spectral solution is defined along the Sommerfeld integration contour and can be evaluated asymptotically to derive high-frequency expressions for the diffracted field. Some numerical results are presented to show that the above solution predicts a non vanishing diffracted field for any incident field polarization, and smoothly converges to the known solutions for both the perfectly conducting half-plane and the unidirectionally conducting half-plane, which are contained in the adopted strip-grating model as limit cases.

Electromagnetic scattering by anisotropic impedance half and full planes illuminated at oblique incidence

The three-dimensional electromagnetic (EM) scattering from half and full plane configurations, both characterized by a perfectly conducting and an anisotropic impedance face, is analyzed. The anisotropic impedance boundary condition considered for the loaded face is suitable for modeling corrugated surfaces or strip-loaded grounded dielectric slabs used to realize artificially hard or soft surfaces, with a tensor surface impedance exhibiting a vanishing impedance along the corrugations or strips and a diverging impedance in the orthogonal direction. Previous rigorous solutions, valid when the vanishing impedance direction is either parallel or perpendicular to the edge, are generalized here to the case in which the direction of vanishing impedance is arbitrarily oriented.

Plane wave scattering by edges in unidirectionally conducting screens

According to its original definition a unidirectionally electrically conducting (UEC) screen is a penetrable anisotropic surface which is perfectly conducting in one direction and perfectly insulating in the orthogonal direction. The scattering of an arbitrarily polarized plane wave obliquely incident on the edge of either a UEC half plane or a planar junction between a UEC screen and a perfectly conducting half plane is analyzed in this paper. The direction of infinite conductivity of the UEC screen is arbitrarily oriented with respect to the edge. Exact closed form expressions for the scattered field are derived, which contain the standard transition function of the uniform geometrical theory of diffraction and simple ratios of trigonometric functions. Specific attention is devoted to the phenomenon of surface wave excitation at the diffracting edge of the structures under investigation. The features of this wave guided by the anisotropic screen are discussed.