High-Impedance Electromagnetic Surfaces with Forbidden Bands at Radio and Microwave Frequencies

A new type of metallic electromagnetic structure has been developed that is characterized by having high surface impedance. The geometry is analogous to a corrugated metal surface in which the corrugations have been folded up into lumped circuit elements, and distributed in a 2-D lattice. Although it is made of continuous metal, and conducts DC currents, it does not conduct AC currents within a forbidden frequency band. Unlike normal conductors, this new surface does not support propagating surface waves. Furthermore, image currents induced in the surface are not phase reversed as they are on a flat metal surface.