An asymptotic boundary condition for corrugated surfaces and its application to calculate scattering from circular cylinders with dielectric filled corrugations

Abstract

In order to analyze corrugated surfaces accurately, the field outside the surface must be expanded in Floquet modes and the field inside in parallel plate waveguide modes. This is very laborious and difficult and is also restricted to certain canonical geometries. An easier approach is to approximate the fields at the interface by an equivalent surface impedance. This approach has known limitations because the surface impedance can only be defined uniquely for specific canonical field problems, e.g., the surface impedance approach does not work when the plane of incidence is not orthogonal to the corrugations because then the surface impedance varies rapidly with the angle of incidence. The paper introduces an asymptotic corrugation boundary condition (ACBC) which does not suffer from the complexity of the Floquet mode technique and the limitations of the surface impedance approach. A similar boundary condition has been introduced for strip-loaded dielectric surfaces.