Using characteristic mode theory to design and analyze an X-band polarization conversion metasurface

This paper proposes a new framework based on the characteristic modes analysis (CMA) to design polarization conversion metasurfaces (PCMs). This approach relies on the information inferred from the characteristic currents of the dominant modes (DMs). To demonstrate the advantages of this strategy, a multi-functional PCM is designed for the X-band frequencies. Besides, this paper expands and develops the characteristic mode rotation (CMR) method to reveal the intrinsic behavior of PCMs in a new manner. In addition, the extended CMR method is utilized for the first time to investigate the physical concepts behind polarization purity and angular stability at the resonance frequencies. Finally, a prototype of the designed polarizer is fabricated and its reflection coefficients are measured. A great agreement between simulation and measurement results is obtained.