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 x- 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.
* Project supported by the Natural Science Foundation of Shaanxi Province, China (Grant Nos. 2019JM-077 and 2018JM-6098), the Scientific Research Program Funded by Shaanxi Provincial Education Department (Grant No. 18JK1195), and the Shaanxi Key Research and Development Project, China (Grant No. 2019GY-055).
Unit cell of proposed polarization conversion metasurface: (a) three-dimensional (3D) view, and (b) top view.
Fig. 2.
Simulated results of proposed polarization conversion metasurface undeer y-polarized normal incidence: (a) phase difference Δ φyx between rxy and ryy and (b) magnitude of rxy and ryy.
Fig. 3.
Axial ratio of reflected wave under y-polarized normal incidence.
Fig. 4.
(a) LTC reflection coefficients and (b) polarization conversion rate (PCR) of proposed polarization conversion metasurface under y-polarized normal incidence.
Fig. 5.
Intuitive schematic diagram of phase difference between co- and cross-polarization reflection coefficients under x- and y-polarized incidences.
Fig. 6.
Simulated results of proposed polarization conversion metasurface under u- and v-polarized normal incidences: (a) phase difference between ruu and rvv, (b) magnitudes and (c) phases of ruu and rvv, (d) axial ratio (AR) of the reflected wave.
Fig. 7.
(a) Photographs of experimental sample, (b) schematic diagram of measurement setup, and (c) measured results: axial ratio (AR) of reflected wave under x- and y-polarized incidences.
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