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

ABSTRACT In this work, a high-efficiency ultra-wideband ellipse-shaped linear-to-circular 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° 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.