Ultra-wideband linear-to-circular polarization conversion metasurface

An ultra-wideband and high-efficiency reflective linear-to-circular polarization conversion metasurface is proposed.The proposed metasurface is composed of a square array of a corner-truncated square patch printed on grounded dielectric substrate and covered with a dielectric layer,which is an orthotropic anisotropic structure with a pair of mutually perpendicular symmetric axes u and v along the directions with the tilt angles of ±45° with respect to the vertical y axis.When the u-and v-polarized waves are incident on the proposed metasurface,the phase difference between the two reflection coefficients is close to-90° in an ultra-wide frequency band,so it can realize high-efficiency and ultra-wideband LTC polarization conversion under both κ-and y-polarized incidences in this band.The proposed polarization conversion metasurface is simulated and measured.Both the simulated and measured results show that the axial ratio(AR) of the reflected wave is kept below 3 dB in the ultra-wide frequency band of 5.87 GHz-21.13 GHz,which is corresponding to a relative bandwidth of 113%;moreover,the polarization conversion rate(PCR) can be kept larger than 99% in a frequency range of 8.08 GHz-20.92 GHz.