基于双层超表面的宽带、高效透射型轨道角动量发生器

提出一种宽带、高传输效率的双层超表面,其单元结构是在介质层两边对称刻蚀结构参数相同的十字型金属贴片且将两层超表面沿y方向错位半个周期长度形成.通过引入y方向的错位,双层超表面的透射带宽得到大幅度提升.同时,采用等效电路理论分析了该双层超表面的带宽展宽机理.在此基础上,进一步结合Pancharatnam-Berry相位原...

Wideband and high efficiency orbital angular momentum generator based on bi-layer metasurface

A broadband and high-efficieny bi-layer metasurface is proposed in this paper.The unit cell of the metasurface is formed by symmetrically etching two cross-type metal patches on both sides of a dielectric plate.Furthermore,the two metal patches have a displacement of half a period along the y-axis.By employing the displacement,the transmission bandwidth of the bi-layer metasurface is significantly expanded.In order to obtain a physical insight into bandwidth broadening,aπ-type equivalent circuit that presents the electromagnetic coupling between within the bi-layer metasurfaces is successfully extracted to investigate the influence of electromagnetic coupling on transmission performance.The results show that by shifting the metal patches along the y-axis by half a period,the coupling impedance(Z12 or Z21)of bi-layer metasurface can be significantly modified,which further changes the electromagnetic coupling of the bi-layer metasurface.Correspondingly,the impedances Zp and Zs in theπ-type circuit are changed to approximately meet the resonant condition of circuit in broadband,resulting in the bandwidth expansion of the proposed device.By using Pancharatnam-Berry phase theory,we redesign the proposed metasurface unit cell into a broadband orbital angular momentum generator.The simulation and measurement results verify that the bi-layer metasurface can convert a left-hand circularly polarized wave into a right-hand circularly polarized wave carrying orbital angular momentum in a frequency range between 11 GHz and 12.8 GHz,demonstrating the performance of device.