Wideband Dual-Circularly Polarized Transmit-Reflect-Array Antenna With Energy Allocation Based on Hybrid Metasurface

This communication presents a design strategy for a wideband bidirectional dual-circularly polarized (DCP) transmit-reflect-array antenna (TRA) that integrates a DCP transmitarray (TA) and a DCP reflectarray (RA). Two types of meta-atoms (MAs), capable of independently manipulating full-space CP phase responses, are designed and incorporated into a shared aperture to construct hybrid metasurfaces. The arrangement of these MAs is optimized using a genetic algorithm (GA), providing four degrees of freedom (DoFs) of beamforming. Modifying the proportion of two types of MAs enables energy allocation (EA) with tailored gain differences between orthogonal CP components. Two DCP TRA prototypes, achieving gain differences of 0 and 5 dB, are fabricated and characterized with a panel thickness of only $0.14~\lambda _{0}$ . The measured bandwidths of the two TRAs exceed 30.7% for TA operation and 44.1% for RA operation, with both the gain variations and axial ratios below 3 dB.