Circularly polarized fabry perot cavity antennas with peripheral roughness in superstrate unit cells

Abstract

A Fabry Perot cavity (FPC) antenna consists of a primary radiator at the base of a dielectric cavity sealed with a partially reflecting surface at the other end. Excitation from the radiator is partially reflected by the reflecting surface back into the cavity that is backed by a ground plane. Multiple reflections within the cavity enhances the gain of the antenna. These antennas have been extensively researched and developed for their reduced fabrication complexity and cost as compared to other high gain planar antennas. Recently, metasurfaces with desirable electromagnetic properties have been engineered for the partially reflecting surface of FPC antennas in order to reduce their profile dimensions. These surfaces usually consist of an array of unit cells that are skillfully designed in order to obtain high bandwidth or desired polarization. In this thesis, we have examined two unit cell designs - arc and rectangular loop with the diagonal - with an objective of achieving circular polarization, broad bandwidth and high gain. Based on simulations, we achieved minimum axial ratios of 7.46 dB and 7.61 dB respectively for these two designs. Then we introduced a new design parameter in the form of peripheral roughness in the edges of each of the unit cells. While the roughness did not significantly improve the axial ratio of the design with the unit cell arc, we demonstrated a wide return loss bandwidth of 202.78 MHz (8.86%), an enhanced gain of 9.48 dBi, and a reduced axial ratio of 4.79 dB for the unit cell with a rectangular loop with diagonal.