A High-Efficiency Reconfigurable Bidirectional Array Antenna Based on Transmit–Reflect Switchable Metasurface

This communication proposes a reconfigurable bidirectional array antenna with high efficiency by employing a novel transmit-reflect switchable metasurface (TRSM) with 360° continuous phase coverage. To realize electromagnetic (EM) wave manipulation, a transmit-reflect switch layer (TRSL) incorporating p-i-n diodes is introduced as the middle layer of TRSM, sandwiched by two transmission metasurfaces (TMs). By on/off the switches, the TRSL functions as a mesh-type ground or a polarization-filtering layer, exhibiting a reconfigurable reflective or transmissive property to the incident wave. Furthermore, the TRSM achieves 360° phase compensation and directive beam formation through combined operation of upper and lower TMs. This structure enables bidirectional radiation at a single frequency and polarization. To minimize structural complexity, an enhanced TRSM design was developed and optimized to achieve a 50% reduction in the number of p-i-n diodes. Since the independent control of bidirectional radiation by TRSL does not interfere with the phase-tuning function of two TMs, the TRSM achieves 360° phase compensation and minimizes quantization errors. Moreover, the use of p-i-n diodes, which are not directly integrated with the radiating elements, reduces insertion loss. Hence, the TRSM maintains a high aperture efficiency. A prototype was fabricated and measured to demonstrate a successful realization of the upward and downward directive beams with peak gains of 22.3 and 22.1 dBi and aperture efficiencies of 47.2% and 43.8% The proposed antenna design presents notable advantages, such as high gain, high aperture efficiency, cost-effectiveness, a simplified configuration, and electronic beam control functionality.