Effect of truncating the superstructures in broadband Fabry-Pèrot cavity antennas

Fabry-Perot cavity antennas, while offering design simplicity and high directivity, are promising candidates for microwave and millimeter wave communication links. Recommendations for effectively truncating the 1-D/2-D periodic structures, designed to act as superstructures in such antennas, are presented. It is shown that the aperture size in such antennas contributes, in part, towards the directivity-bandwidth product. A simple Fabry-Perot cavity antenna which uses a two layered 1-D Electromagnetic Band Gap (EBG) structure as its superstructure is studied to quantify the effects of aperture size on peak directivity and half-power directivity-bandwidth. Conventional aperture size for such antennas ranges from 5-6λ02, which results in over-dimensioning as well as narrowband behavior. It is shown that comparable performance with existing designs can be achieved by using much smaller aperture sizes and thus reducing the antenna footprint. This work serves as a guide to effectively choose and fine-tune aperture sizes for Fabry-Perot cavity antennas, thus reducing the redundant computational load in the full-scale design process.