An effective-medium model for high-impedance surfaces

We show that high-impedance surfaces with complex microstructures can be well described by a double-layer effective-medium model consisting of an anisotropic meta-material layer (with a dispersive permeability mu) put on top of a metal sheet. We predict that a complete surface wave (SW) gap exists in such a system when the condition 0 < 1 is fulfilled, and we verify this prediction by finite-difference-time-domain (FDTD) simulations on realistic structures. We argue that opening a SW gap in the in-phase reflection regime requires an additional mechanism for such kinds of systems, and demonstrate this argument via FDTD simulations on two commonly adopted structures.