Annular Slot Loaded High-Impedance Ground Plane

High-impedance surfaces like electromagnetic band gap (EBG) ground planes have been used to realize low profile antennas. In this paper, an alternative ground plane design is presented for antennas with circular current distributions, which consists of an annular slot backed by a thin grounded substrate. The slot ring generates a high-impedance condition at a resonant frequency in the vicinity of the slot. This annular slot loaded ground plane results in efficient radiation of the low profile antenna in the broadside direction. Since the slot loaded ground plane consists of a single slot ring rather than periodic structures, it is much simpler to construct than the standard EBG ground plane. Numerical simulations and experimental measurements are shown to validate the design concept and are compared with a mushroom-type EBG ground plane. A parametric analysis was also conducted by varying the slot ring´s dimensions and tuning varactors are shown to vary the ground plane´s resonant frequency.