Circular-Polarization-Selective Metasurface and Its Applications to Transmit-Reflect-Array Antenna and Bidirectional Antenna

In this article, a cascaded metasurface (MS) with circular-polarization-selective properties is proposed, which can achieve high reflection for left-handed circular polarization (LCP) and high transmission for right-handed circular polarization (RCP). Such MS, constructed by cascading two kinds of MS sheets, can conduct decoupled geometric phase modulations for the LCP reflection channel and RCP transmission channel by respectively rotating the two elements in the two MS sheets. In order to show its practical applications, first, the proposed MS is applied to design a reconfigurable circularly polarized (CP) transmit-reflect-array antenna (TRA) that can be switched between a high-gain LCP transmitarray antenna and a high-gain LCP reflectarray antenna (RA) dependent on the polarization state of the feed antenna. The simulated results validate its function-switchable and high-gain characteristics. Second, a CP bidirectional antenna is designed utilizing the proposed MS and validated by a fabricated prototype with good agreement between the measured and simulated performances. The results indicate that the joint bandwidth (BW) for both forward and backward aperture efficiencies larger than 20% and axial ratios smaller than 3 dB is about 16% (9.4–11 GHz), across which the antenna realizes bidirectional high-gain and high-purity LCP radiations.