Higher order impedance boundary conditions revisited: application to chiral coatings

Abstract

In this paper, a novel spectral domain method for obtaining higher order impedance boundary conditions for the problem of electromagnetic scattering from complex coatings is described. The method is then applied to the specific case of chiral coatings on conductors. The present method for obtaining the boundary conditions is quite general, and is applicable to coatings with arbitrary constitutive relations, including anisotropic coatings, such as dielectric layers with tensor permittivity, and non-reciprocal coatings, such as magnetically biased ferrites. Multiple layers may also be handled in a systematic manner. Although the examples presented focus on boundary conditions containing tangential derivatives no higher than second order, an extension to higher order conditions is also straight forward. The standard impedance boundary condition (SIBC), tensor impedance boundary condition (TIBC), and the generalized impedance boundary conditions (GIBC), are contained as special cases of the general method described in this paper. It is also shown how the general method presented allows the effects of curvature to be included in the boundary condition. The examples presented include a number of planar chiral layers and chiral coated circular cylinders, and illustrate the accuracy of the proposed boundary conditions.