An ultra-wideband ellipse-shaped linear-to-circular polarization conversion metasurface with high efficiency

In this work, a high-efficiency ultra-wideband ellipse-shaped linear-tocircular polarization conversion metasurface is proposed. The metasurface is composed of a square array of ellipse-shaped metal patches printed on grounded dielectric substrate and covered by a dielectric layer, because it is an orthogonal anisotropic structure with a pair of mutually perpendicular symmetric axes u and v along the directions +/- 45 degrees with respect to the vertical y-axis, and the reflection phase difference under u- and v-polarized incidences is very close to -90 in an ultra-wide frequency ranges, both theoretical prediction and numerical simulation show that the metasurface can achieve high-efficiency ultra-wideband linear-to-circular polarization conversion under x- and y-polarized incidences, its 3-dB axial-ratio (AR) band is between 7.08 and 25.86 GHz with a relative bandwidth of 114%, in particular, the AR of its reflected wave can be kept lower than 0.89 dB in the frequency range 7.65-25.32 GHz, in which the polarization conversion rate (PCR) is always larger than 99.73%. Finally, one effective experimental verification is carried out, and a reasonable agreement is observed between the simulation and experimental results. Therefore, the polarization conversion metasurface has great potential application values in various polarization-controlled devices.