Anisotropic metasurface-based linear-to-orthogonal linear, circular and elliptical reflective polariser for 6G FR-3 sub-band applications

This paper presents a meta-surface based, anisotropic retro polarisation converter, operating over the electromagnetic spectrum of FR3 band. It provides polarisation conversions from linear-to-orthogonal linear, circular and elliptical polarisations across the sub-band of FR3 [i.e.; C-band (partially), X-band, Ku-band and K-band (partially), as per IEEE spectrum category]. The proposed unit cell consists of a single FR-4 substrate backed by a metallic ground plane, while the top surface contains a split-ring resonator loaded with diagonally placed equals-sign-shaped metallic resonators. It operates as a linear-to-circular polarisation converter across 7.4–8.6 GHz, 9.2–14.4 GHz and 17–17.8 GHz. It also offers linear‑to‑cross polarisation conversion characteristics at 9 GHz, 15.4–16.7 GHz and 18.8–18.9 GHz, and as a linear-to-elliptical converter in remaining spectrum. The proposed structure can find potential applications for polarisation-sensitive applications, such as reconfigurable antennas, radar cross-section (RCS) reduction and multifunctional reflective surfaces in communication systems for selected 6 G FR-3 sub-band applications.