超宽带共极化相位梯度超表面的设计

Design of ultra-wideband co-polarized phase gradient metasurface

为了实现电磁波的传播和共极化特性调控,利用PB几何相位理论设计了一种基于“弯工”形的金属结构超表面,采用10种不同的单元进行空间排布,每个相邻单元相位差为π10,实现了0~2π相位内的反射波相位调控。基于广义斯涅尔定律构建了相对带宽为57.3%的相位梯度超表面,其基本单元由顶层弯工形金属结构、中间为介质层与底层铜金属板组成。通过在不同频点处分别入射线极化波和圆极化波,能够实现对任意波束入射下的反射波束的偏转调控。仿真了在不同频点下的反射波束的偏转角度,并且与理论结果相一致。在设计频段范围内其共极化转换效率达90%以上,镜面反射率在-20 dB以下。通过测试所制作的超表面的镜面反射率为-15 dB与仿真结果基本相吻合。与传统超表面相比,所设计的超表面其频带范围在18.8~33.9 GHz,具有宽频带、高极化转换率、体积小、成本低的优点。该超表面能够应用在诸多方面如5G技术、高增益天线、超宽带隐身和雷达散射RCS等。

A metal-structured metasurface based on the"bend I"shape is designed by means of Pancharatnam-Berry(PB)geometric phase theory to realize the propagation of electromagnetic waves and the regulation of the co-polarization characteristics.In the design,10 kinds of units are used for spatial arrangement(the phase difference of two adjacent units is π/10),which realizes the phase regulation of the reflected wave within the 0~2π phase.On the basis of the generalized Snell′s law,a phase gradient metasurface with a relative bandwidth of 57.3% is constructed.Its basic unit is composed of a bend I-shaped metal structure on the top,a dielectric layer in the middle and a copper metal plate on the bottom.The deflection control of the reflected beam in the case of arbitrary beam incidence can be realized by separately entering linear polarization waves and circular polarization waves at different frequency points.The deflection angle of the reflected beam at different frequency points is simulated,and the simulation results are consistent with the theoretical results.In the range of the designed frequency band,the co-polarization conversion efficiency of the metasurface is more than 90%,and its specular reflectance is below-20 dB.By the test,the specular reflectivity of the designed metasurface is-15 dB,which is basically in agreement with the simulation results.In comparison with the traditional metasurface,the frequency band of the designed metasurfase is in the range of 18.8~33.9 GHz,which has the advantages of wide frequency band,high polarization conversion rate,small volume and low cost.The metasurface can be used in many areas,such as 5G technology,high-gain antennas,ultra-wideband stealth and RCS.