Abstract
An ultra-wideband linear polarization converter based on a reflecting metasurface is presented. The polarizer is composed by a periodic arrangement of miniaturized metallic elements printed on a grounded dielectric substrate. In order to achieve broadband polarization converting properties, the metasurface is optimized by employing a genetic algorithm (GA) which imposes the minimization of the amplitude of the co-polar reflection coefficient over a wide frequency band. The enhanced angular stability of the polarization converter is due to the miniaturized unit cell which is obtained by imposing the maximum periodicity of the metasurface in the GA optimization process. The pixelated polarization converter obtained by the GA exhibits a relative bandwidth of 102% working from 8.12 GHz to 25.16 GHz. The analysis of the surface current distribution of the metasurface led to a methodology for refining the optimized GA solution based on the sequential removal of pixels of the unit cell on which surface currents are not excited. The relative bandwidth of the refined polarizer is extended up to 117.8% with a unit cell periodicity of 0.46 mm, corresponding to λ/20 at the maximum operating frequency. The performance of the proposed ultra-wideband polarization metasurface has been confirmed through full-wave simulations and measurements.
Highlights
In order to understand whether the pixel removed is necessary or not to the metasurface, the reflection coefficient R yx calculated by the full wave is compared against the cross-polar reflection coefficient of the original unit cell Ryx
The pixelated unit cell topology has been optimized with a genetic algorithm (GA) in conjunction with a full-wave code based on a Periodic Method of Moments
The miniaturized unit cell is obtained limiting the maximum periodicity of the metasurface in the optimization process
Summary
Michele Borgese , Filippo Costa , Simone Genovesi, Agostino Monorchio & Giuliano Manara. The unit cell is composed by a square-shaped resonator with diagonal and metallic ground sheet separated by dielectric substrate with a thickness of 3 mm This polarization converter exhibits a relative bandwidth of 91.2% working from 7.57 GHz to 20.46 GHz. The presence of the ground plane in reflective metasurfaces allows for the reflection of almost all electromagnetic energy impinging on the surface. This kind of devices are widely used for military applications in the microwave regime for the design of stealth surfaces In these cases, wideband polarization converters (as the polarizer presented in the paper) are needed. An ultra-wideband polarization converter based on a single-layer reflective metasurface is presented This device is able to perform a linear-to-linear polarization conversion for an orthogonal incidence of the EM wave.
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