Broadband electrically tunable linear polarization converter based on a graphene metasurface

In this study, a broadband tunable reflective graphene-based linear polarization converter (GLPC) is proposed based on the graphene-ionic liquid-ITO structure (GIIS) integrated with a periodic double split ring resonator (DSRR) in the millimeter-wave regime. The tuning characteristic of the designed GLPC is analyzed using full-wave simulations and the equivalent circuit model method (ECM), which is based on multi-section transmission lines. There is a good agreement between ECM and simulation results. A comprehensive physical mechanism for the proposed broadband GLPC is then achieved by analyzing the surface current distributions. After manufacturing, the GLPC prototype's co- and cross-polarized reflection coefficients were measured using various bias voltages. The reflectivity can be controlled from -4.5 to -20 dB by changing the bias voltage in the range of +1.1 to -3.3 V. The designed GLPC can provide a tunable polarization conversion within the frequency range of 15.5∼35 GHz and shows a more than 75% conversion efficiency. The results of the simulation and the measurement are also in good agreement. The designed GLPC has potential applications in radar cross-section reduction, antenna design, and stealth technology by reconfiguring its polarized reflection characteristic dynamically.