Metasurface with high cross-polarization isolation using rectangular split rings for simultaneous amplitude and phase controls

Metasurfaces have demonstrated significant potential for versatile modulation of electromagnetic waves. To enhance the control of electromagnetic waves, simultaneous control of amplitudes and phases is often essential in certain applications. The C-shaped split ring (SR) with polarization conversion and its deformed structures can fulfill this requirement; however, such structures encounter the challenge of low polarization isolation, which is mainly reflected in its inherent characteristics of low polarization isolation and the deterioration of polarization isolation in amplitude control. In this paper, a reflective metasurface with improved polarization isolation is proposed. The designed metasurface consists of rectangular split ring (R-SR) elements, which can realize both amplitude and phase controls simultaneously and independently while exhibiting higher polarization isolation than the conventional SR element. Furthermore, an alternating mirror rotation method (AMRM) for the arrangement of amplitude-control elements is proposed to suppress the degradation of polarization isolation caused by amplitude control. Several metasurfaces are designed to verify the characteristics of the proposed R-SR structure and the effectiveness of the AMRM. Finally, two reflective metasurfaces composed of R-SR elements and SR elements with identical configurations are designed and manufactured. Both the simulation and measured results demonstrate the versatility of the proposed design and its advantages in terms of polarization isolation and transfer efficiency.