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 investigate the intrinsic behavior of PCMs. Based on the extended CMR method, the physical concepts behind polarization conversion purity and angular stability at the resonance frequencies are revealed in a new manner. 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.