Gain enhancement of microstrip reflectarray incorporating a PBG structure

Reflectarray combines the features of the reflector and array and was first introduced in 1963. The microstrip reflectarray antenna is a planar antenna, printed on a dielectric substrate. It consists of thousands of microstrip elements specifically designed so that the scattered field from each of the elements yields a proper differential phase to achieve a focusing effect. Since the major part of the antenna is a flat structure with a low profile, the antenna can be mounted flush on a building and it is easy to fabricate and install. There are two key issues regarding the performance of microstrip reflectarrays. The first one is its narrow bandwidth and the second one is its efficiency. A novel approach for gain enhancement of microstrip reflectarrays is proposed. A 7/spl times/7 elements microstrip reflectarray with a PBG ground plane was designed and measured. It is found that by incorporating a PBG that consists of a periodic array of square perforations in the ground plane, the antenna gain can be improved by 2.8 dB than that without the PBG.