Optimal Design of Miniaturized Reflecting Metasurfaces for Ultra-Wideband and Angularly Stable Polarization Conversion

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.

Ultrawideband Spin‐Decoupled Coding Metasurface for Independent Dual‐Channel Wavefront Tailoring

“…On the other hand, the reflective half‐wave plate element has a Jones matrix described as: with off‐diagonal symmetry to realize the polarization conversion effect. Here, Φ 0 shows the original phase of the half‐wave plate element.…”

“…The above results reveal that the challenge to design broadband spin‐decoupled metasurface can be reduced to find broadband half‐wave plates with different original phases. The literatures of metamaterial fields have explored many methods to manipulate the polarization state of EM wave in a broad band, and this may provide possible solutions.…”

“…In this work, we propose a digital strategy to realize ultrawideband spin‐decoupled metasurface capable of independently encoding distinct wavefronts into orthogonal spin channels. Through theoretical analysis, we find that the hybrid method integrating both propagation and geometric phases can be simplified to seek different half‐wave plate meta‐atoms with different original phases. By utilizing digital and coding metasurface, a type of metasurface employing discrete phase elements to achieve diverse wave functions, we further get additional degree of freedom that is quite conducive to broadening the bandwidth as well as reducing the complexity of the design process.…”

Low-Cost Portable Reader for Frequency Domain Chipless Tags: Architecture and Experimental Results on Depolarizing Tags

“…The tags are formed by a series of dipoles of different length placed at an adequate distance from a metallic ground plane. The two-layer surface acts as a multi-frequency polarization converter [14,15]. The device is able to convert the polarization of the impinging wave only when the angle of incidence is close to 45 • with respect to the orientation of the dipole.…”

A coding optimized polarization conversion metasurface in broadband and wide‐angle

“…However, these metasurfaces are designed by tentative simulations and manual parameter optimizations. In order to improve the design efficiency, optimization algorithms were considered to design metasurfaces . In Reference , a broadband polarization conversion metasurface for normal incidence is designed using genetic algorithms.…”