A novel reflective FSS for polarization conversion and enhanced angular stability

In this paper, a novel reflective linear-to-circular polarization Frequency-Selective Surface (LTCP-FSS) for X-band applications is presented. Initially, the design uses an orthotropic elliptical ring arranged in an orthotropic direction with the symmetric of orthogonal axes (u and v) oriented at 45° from the x or y direction. The incident X and Y polarized waves are converted to circular polarization in reflective mode through the orthotropic elliptical rings, which maintain equal amplitude and a ± 90° phase difference between the x and y direction electric field components. The bandwidth of the proposed FSS is further enhanced by loading resonator elements around the elliptical ring in an orthotropic orientation. This addition introduces extra harmonics alongside the elliptical ring harmonics, resulting in enhanced bandwidth and improved angular stability. The proposed LTCP-FSS is validated using an equivalent circuit model (ECM) and hardware measurements. It has a 43.45% (7.2–11.2 GHz) polarization conversion bandwidth and a 38.25% (7.4–10.9 GHz) 3dB axial ratio relative bandwidth for right-hand circular polarization (RHCP). The polarization conversion ratio (PCR) is above 95% in the 7.2–11.2 GHz frequency range. Additionally, it shows good angular stability up to 60° of the incident waves.