Influence of a curved FSS on the radiation patterns of an enclosed source

In order to study the effects of a dielectric embedded FSS on an enclosed antenna pattern, the authors adopt the ray tracing technique to compute the near field pattern of the antenna-FSS configuration exterior to the structure, from which the transmission coefficient and the far field patterns can be calculated. They use parabolic and paraboloidal shapes formed from a dielectric slab with an embedded slot ring FSS which, when it is planar, provides a flat passband transmission window. Rings have been chosen with a view to minimise polarization dependence of the element although the method is applicable to arbitrary FSS arrays and surfaces of arbitrary shape. The approach adopted is based on tracing multiple ray paths through the curved dielectric slab with the FSS treated as an infinitesimally thin interface with known reflection and transmission coefficients. In this manner, a structure composed of an FSS embedded in a dielectric can be treated as a series of interfaces where the incident ray is partially specularly reflected and partially transmitted according to the reflection and transmission dyadics at the point of incidence, until it emerges on the other side of the radome or decays to a level below a prescribed threshold. With a sufficiently dense bundle of input rays from the source, the radiation pattern transmitted through the radome can be computed using two dimensional interpolation on the transmitted rays