A Novel Design Method for High-Efficiency Quasi-2-bit Reconfigurable Metasurface Antennas

This communication proposes a novel design method for a quasi-2-bit reconfigurable metasurface antenna (RMA) to improve aperture efficiency using a simple bias circuit. The quasi-2-bit RMA is designed by combining two types of 1-bit unit cells to achieve four quantized phase states, which results in quantization efficiencies similar to an ideal 2-bit for a specific direction while maintaining a simple 1-bit bias circuit. Furthermore, this RMA can also be designed for multiple beam directions by optimizing the combination of the 1-bit unit cells using the least square method. The quasi-2-bit RMA is then experimentally verified by fabricating a structure optimized for two beam switching angles of ±18° in the E-plane. The aperture efficiencies of the quasi-2-bit RMA are measured to be 25.1% for - 18° and 28.1% for 18°, respectively. Compared to 1-bit RMAs, the measured aperture efficiency of the quasi-2-bit RMA is improved by 61.49% for the - 18° beam and by 114.2% for the 18° beam, respectively.