Triple-band linear-to-circular polarization converter via tailored asymmetry in single-layer metasurface

This paper proposes a single-layer, triple-band linear-to-circular metasurface (LTCM) polarization converter designed with tailored asymmetry. The structure of LTCM consists of a single dielectric substrate with patterned metal on both sides, featuring double-open ‘I’ shapes printed on each side and rotated 90° counter-clockwise in the transmission direction to break symmetry and form a chiral structure. This design enhances the quality of circularly polarized waves by adding bar-shaped branches. The LTCM utilizes the asymmetric transmission effect to produce high-quality circularly polarized waves. It converts a y-polarized wave into left-hand circularly polarized (LHCP) waves within the 8.170-8.270 GHz and 13.509-13.574 GHz bands, and into right-hand circularly polarized (RHCP) waves within the 11.705-11.809 GHz band. Additionally, it can transform an x-polarized wave into RHCP at 8.170–8.270 GHz, and into LHCP at 11.705–11.809 GHz and 13.509–13.574 GHz. The axial ratio stays below 3 dB, and the device maintains angular stability up to 30°. The LTCM was fabricated, and the simulated results were confirmed through measurements.