A high-impedance surface using annular-slot-loaded ground plane

This paper presents a simple realization of a high impedance surface that can be used for low profile antennas with circular current distributions. The surface consists of an annular slot backed by a thin grounded substrate. The annular-slot-loaded ground plane reflects incident radiation with a phase centered at 0-dgrees at a resonance frequency that is a function of the slot and substrate parameters. This enhances the radiation in the broadside direction. Simulation and measurement results of a loop antenna validate the design concept and are compared with a mushroom-type EBG ground plane. A parametric analysis is also conducted with a spiral antenna placed above the annular-slot-loaded ground plane.