Mechanically Frequency-Reconfigurable and Circularly Polarized Fabry-Pérot Cavity Antenna

A left-handed circularly polarized (LHCP) and frequency reconfigurable Fabry-Pérot cavity antenna (FPCA) is proposed using mechanically reconfigurable Fabry-Pérot cavity (FPC). By using chiral metasurfaces as the top and bottom boundaries of the FPC, LHCP waves can be multiply reflected within the cavity while preserving the same handedness. Moreover, the resonant frequency is directly dependent on its twist angle. Hence, the antenna can realize frequency reconfiguration by rotating the chiral partially reflective surface (PRS). The chiral bottom reflector is designed with low polarization loss. Additionally, a chiral PRS is designed to achieve both chiral reflection and polarization-stable transmission during the rotation of the PRS, ensuring stable LHCP radiation during reconfiguration. Finally, a Fabry-Pérot cavity antenna is obtained under the excitation of an LHCP source antenna. It achieves narrowband performance in terms of gain and axial ratio bandwidth with a high directionality. Moreover, a wide and continuous frequency reconfiguration range of peak gain is realized from 5 to 6.02 GHz. The maximum peak gain of 19.98 dBic with a variation of less than 1.9 dB is realized. Maximum aperture efficiency reaches 55.55%. A prototype has been fabricated and measured for verification. Both simulation and measurement results show good agreement, confirming the feasibility of the proposed design method.