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In this work, a metasurface with the symmetrical double C-shaped narrow ring connected with the central cross structure is investigated by simulation, theory and experiment, which can near-perfectly convert linearly polarized electromagnetic waves into their orthogonal components in the frequency ranges from 9.38 to 13.36 GHz and 14.84 to 20.36 GHz. And the corresponding fractional bandwidths within the two bands are 35.00% and 31.36%, respectively. The influences of structural parameters on the polarization conversion performance are studied. The results show that the central frequencies and bandwidths of the two bands can be easily modulated by varying the structural parameters of r and θ. The high-efficiency and dual-broadband characteristics can also be well maintained in the oblique incidence range of 0-45°. Meanwhile, the mechanisms of polarization conversion are analysed, and several formulas are used to calculate the reflection coefficients of the co-and cross-polarization under the normal incident y-polarized electromagnetic waves based on the phase difference of the reflection coefficients of the uand v-polarized conversions. The experiment results are in good agreement with those of simulations and theoretical analysis. The proposed metasurface has important applications in novel polarization control devices.

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A dual-broadband and high-efficiency reflective linear polarization converter based on an anisotropic metasurface is presented. The device consists of two symmetrical, double-slotted metallic split-rings and one criss-cross structure, a dielectric layer, and a completely reflective metallic ground. The converter exhibits four resonances and can near-perfectly convert x- or y-polarized incident waves into cross-polarized waves in the frequency ranges of 9.38–13.36 GHz and 14.84–20.36 GHz. The polarization conversion ratios (PCRs) of the two bands are 98.21% and 99.32%, respectively. The energy conversion ratio (ECR) for energy loss measurement is almost 100% in these frequency bands. The polarization conversion principle is studied. The bandwidths and PCRs of the two bands are determined by varying the dielectric layer thickness. The simulation results are consistent with experimental observations. The designed dual-broadband and high-efficiency metasurface has great potential in the application of electromagnetic polarization control.

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A dual-wideband coding metasurface based on the polarization conversion for radar cross section (RCS) reduction is proposed. An anisotropic element with rotational symmetry is denoted as '0' or '1' in 1-bit coding sequences. The unit cells are arranged according to a binary coded matrix formed by simulated annealing algorithm. The optimal coding metasurface possesses RCS reduction of greater than 10 dB in 9.9-14.1 and 15.6-20.6 GHz while simultaneously maintaining an effective specular reflection performance from 14.1 to 15.6 GHz under x-polarized normal incidence. This shows that the designed optimal coding metasurface has the performance of frequency selectivity. Additionally, the proposed optimal coding metasurface in this paper has polarization insensitive characteristics. The experiment results of the prepared prototype are found to be in line with the numerical simulation results. It is a novel and practical method to achieve low-backward scattering by a combination of diffusion and reflection. The optimal coding metasurface offers huge potential applications for complex electromagnetic wave manipulation, such as stealth fields and antenna designs.

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