Abstract
Electromagnetic bandgap (EBG) structures and frequency selective surfaces (FSSs) can be employed to control electromagnetic-wave propagation in special directions. They have been widely employed as superstrates of Fabry-Perot (FP) antennas (or called planar resonator antenna) for low-profile directive antennas to as spatial angular filters. Extensive effects have been made in FP antennas for high directivity without complex feed networks like conventional antenna array. First, A novel approach for reducing sidelobe levels of compact FP antennas is presented in this study. Perfect electrical conductors (PECs) and Perfect magnetic conductors (PMCs) are employed as cavity sidewalls of FP antennas for reducing the sidelobes caused by reducing the antenna size. A quarter-wave transformer along with a PEC is employed to function as a PMC in this study for real applications. The compact FP antennas with high-directivity (~15 dBi) and low sidelobe levels (-25 dB) both in the E- and H-planes are designed. This antenna can be applied to the antennas of short-range vehicular radars. Then, A novel design of switchable FP antennas for reducing the antenna area is presented in this study. A reconfigurable FSS is employed as a superstrate of a switchable FP antenna. The switchable FP antenna has two performances in one antenna structure switched by bias voltages of PIN diodes. This antenna will be expect to as the antennas of automotive radars that need both high- and low-directivity antennas.