Bidirectional and Circularly Polarized Fabry-Perot Antenna Based on Self-Complementary Metasurface for Millimeter-Wave Applications

In this paper, a practical design to achieve bidirectional radiation and polarization conversion in a Fabry-Perot resonator antenna (FPRA) is proposed. The proposed design utilizes quasi-self-complementary and frequency-selective surfaces (SC-FSS) that are printed on a single dielectric substrate. The self-complementary surface (SCS) has been demonstrated to ensure a consistent 90° phase shift between orthogonal linear polarizations. Frequency-selective surface (FSS) is combined to enhance the reflection magnitude for high gain without affecting the polarization conversion characteristics. Based on the principle of symmetry, the SC-FSS unit is changed and modified to substitute the full reflection ground in the FPRA. This modification is initially proposed to realize bidirectional, circularly polarized (CP), and high-gain radiation in the FPRA. A 45° rotating patch antenna serves as the linearly polarized (LP) feed source. The impedance bandwidth of FPRA is 24.4–25.3 GHz. At 24.8 GHz, the maximum gain at theta = 0° and 180° is 14.2 dBi and 13 dBi, respectively. The polarization conversion bandwidth and 3 dB gain bandwidth are 24.4–25.2 GHz. The radiation properties in the upward and downward directions exhibit good consistency. Furthermore, the left-hand or right-hand CP radiation can be modified by altering the position of the feed, utilizing the same SC-FSS.