To overcome the narrow axial ratio (AR) bandwidth inherent in conventional linearly to circularly polarised converters, this research proposes a metasurface (MS) with a diamond-shaped configuration that can mitigate the effect of surface wave (SW) along the MS edge and achieve a wider 3 dB AR bandwidth. The diamond-shaped MS structure is realised by slanting a square MS by 45°, and it consists of constituent unit cells of rectangular and arbitrary shapes. The rectangular unit cells are positioned 45° to the square dielectric substrate, and the unit cells along the MS edge are partially cut into arbitrary shape to be perfectly aligned along the edge. The 3 dB AR bandwidths and degradation of the MS are characterised by SW and magnetic current distribution. Simulations are carried out and an MS prototype is fabricated to verify the results. The effects of partially cut unit cells (PCUCs) along the MS edge on the SW are characterised. The simulation and measured 3 dB AR bandwidths of the diamond-shaped MS are 37.6 and 28.8%, respectively. The novelty of the proposed diamond-shaped MS polarisation converter lies in the implementation of arbitrary-shaped PCUCs and the use of the diamond-shaped configuration in place of conventional square geometry to realise wider AR bandwidth.

中文翻译：

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使用菱形反射超表面的宽带线性到圆偏振转换

为了克服传统线性到圆极化转换器固有的窄轴比（AR）带宽，本研究提出了一种菱形配置的超表面（MS），可以减轻沿MS边缘的表面波（SW）的影响并实现3 dB的AR带宽。菱形MS结构是通过将方形MS倾斜45°来实现的，它由矩形和任意形状的组成单元构成。矩形单元与方形电介质基板成45°角，沿MS边缘的单元被部分切割为任意形状，以沿边缘完美对齐。3 dB的AR带宽和MS的降级由SW和磁电流分布来表征。进行了仿真，并制造了MS原型以验证结果。表征了沿着SW上MS边缘的部分切割的晶胞（PCUC）的作用。菱形MS的仿真和测得的3 dB AR带宽分别为37.6和28.8％。所提出的菱形MS偏振转换器的新颖之处在于任意形状PCUC的实现以及菱形配置的使用，以代替传统的方形几何形状以实现更宽的AR带宽。