In this work, an ultra-wideband gradient metasurface (GM) is designed by using Pancharatnam–Berry (PB) phase. In the design process, a circular polarisation (CP)-maintaining metasurface (CMM) is proposed at first, which can realise ultra-wideband CP-maintaining reflection in the frequency band of 7.7–19.9 GHz, moreover, PB phase will be generated in its co-polarised reflection coefficient under CP incidence by rotating the anisotropic resonators in its unit cells. Thus, based on the CMM, an ultra-wideband GM is designed by using PB phase. Both the simulation and experiment show that the designed GM can realise ultra-wideband anomalous reflection under arbitrary polarised incidence, the reflected wave under CP incidence will be deflected to an anomalous direction and even be converted to a surface wave; but under linearly polarised and elliptically polarised incidences, the reflected wave will be separated into two beams. In addition, to design more anomalous reflection metasurfaces, the generation principle of PB phase, together with the root cause of the CP-maintaining reflection of the proposed CMM, has been analysed in detail in the designing process.

中文翻译：

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梯度超表面实现的超宽带异常反射

在这项工作中，通过使用Pancharatnam–Berry（PB）相设计了超宽带梯度超表面（GM）。在设计过程中，首先提出了保持圆偏振（CP）的超颖表面（CMM），它可以在7.7-19.9 GHz的频带内实现超宽带的CP保持反射，此外，在通过旋转其晶胞中的各向异性谐振器，其在CP入射下的同极化反射系数。因此，基于CMM，通过使用PB相位设计了超宽带GM。仿真和实验均表明，所设计的GM可以在任意偏振入射下实现超宽带异常反射，CP入射下的反射波会偏转到异常方向，甚至转换为表面波。但是在线性偏振和椭圆偏振入射下，反射波将分成两束。另外，为了设计更多反常的反射超表面，在设计过程中详细分析了PB相的产生原理，以及所提出的CMM保持CP的反射的根本原因。