Metasurface-based conformal linear-to-circular polarization converter for emerging wireless applications

This paper proposes the analysis and design aspects of a metasurface-based reflective type linear-to-circular polarization (LCP) converter in both planar and conformal profiles. The metasurface unit cell consists of a diagonally placed split circular metallic ring on top of a metal backed dielectric substrate. The structure provides LCP conversion with axial ratio (AR) < 3 dB at two frequency bands, which are 27.38–28.61 GHz and 33.1–52 GHz corresponding to fractional bandwidths of 4.4% and 44.5%, respectively. It exhibits two different handedness at the aforementioned two bands for a TE (or TM) linearly polarized incident wave. Moreover, it shows dual polarized and angularly stable (up to 25°) characteristics. It is observed from the far-field characteristics that the LCP converter with an array of 29 × 29 unit cells (12λ ×12λ) produces peak gain of 26 dBi, cross polarization level 20 dB below the maximum main lobe level when illuminated by a linearly polarized source at far-field. Subsequently, the same unit cell is used to design a cylindrical conformal metasurface with different radius of curvatures (r). It provides quite stable AR, gain and radiation patterns till r=100 mm. The array has been fabricated to experimentally validate the numerical results of both the planar and conformal geometries. © 2023 Elsevier GmbH