A closely spaced dual-band dual-sense linear-to-circular polarization converter for X-band applications

This paper presents a novel design of closely spaced dual-band dual-sense linear-to-circular polarization converting metasurface for X-band applications. The unit cell of the metasurface consists of a pair of L-shaped dipoles and a pair of cross-dipoles, respectively, with diagonal symmetry. The proposed linear-to-circular polarization converter (LCPC) provides a 3-dB axial ratio bandwidth (ARBW) ranging from 7.84 to 9.08 GHz (14.65%) for the lower band, and from 10.89 to 12.94 GHz (17.11%) for the upper band. The two frequency bands are in close proximity to each other, with a calculated separation bandwidth of 33.95%. Moreover, the proposed metasurface provides dual-sense operation, enabling polarization conversion to left-hand circular polarization (LHCP) in the lower band and right-hand circular polarization (RHCP) in the upper band for a $y$-polarized incidence wave and vice versa for an $x$-polarized incidence wave, respectively. These characteristics hold significant importance in different applications, such as satellite communication, that demand polarization diversity. After numerical analysis based on full-wave simulations, the proposed converter is fabricated and measured. A good agreement is observed between the full-wave simulated and measurement results.