An equivalent circuit (EC) model for the frequency-selective surfaces (FSSs) comprising anisotropic elements is presented. The periodic surface is initially simulated with an arbitrary azimuthal incidence angle, and its surface impedance matrix is derived. The impedance matrix is subsequently rotated by an angle $\varphi ^{rot}$ on the crystal axes $\chi _{1}$ and $\chi _{2}$ , thus nullifying its extra diagonal terms. The rotation angle $\varphi ^{rot}$ is derived according to the spectral theorem by using the terms of the matrix initially extracted. The diagonal terms of the rotated matrix, that is, the impedances $Z_{\chi _{1}}$ and $Z_{\chi _{2}}$ , are finally matched with the simple LC networks. The circuit model representation of the anisotropic element can be used to analyze the anisotropic FSSs rotated by a generic azimuth angle. The methodology provides a compact description of the generic FSS elements with only five parameters: the lumped parameters of the LC network $L_{\chi _{1}}$ , $C_{\chi _{1}}$ , $L_{\chi _{2}}$ , $C_{\chi _{2}}$ and the rotation angle $\varphi ^{rot}$ . The circuit model can consider the presence of the dielectric substrates close to the FSS or a variation in the FSS periodicity without additional computational efforts. The EC model is finally applied to the design of the two transmitting polarization converters based on the anisotropic metasurfaces.

中文翻译：

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各向异性频率选择表面和超表面的简单等效电路方法

提出了包含各向异性元件的频率选择表面 (FSS) 的等效电路 (EC) 模型。周期性表面最初以任意方位角入射角进行模拟，并推导出其表面阻抗矩阵。阻抗矩阵随后旋转一个角度 $\varphi ^{腐烂}$ 在晶轴上 $\chi _{1}$ 和 $\chi _{2}$ ，从而消除其额外的对角线项。旋转角度 $\varphi ^{腐烂}$ 是根据谱定理通过使用最初提取的矩阵的项导出的。旋转矩阵的对角项，即阻抗 $Z_{\chi _{1}}$ 和 $Z_{\chi _{2}}$ , 最终与简单的匹配 液晶显示器网络。各向异性元件的电路模型表示可用于分析按通用方位角旋转的各向异性 FSS。该方法提供了对通用 FSS 元素的简洁描述，只有五个参数：液晶显示器 网络 $L_{\chi _{1}}$ , $C_{\chi _{1}}$ , $L_{\chi _{2}}$ , $C_{\chi _{2}}$ 和旋转角度 $\varphi ^{腐烂}$ . 电路模型可以考虑靠近 FSS 的介电基板的存在或 FSS 周期性的变化，而无需额外的计算工作。EC模型最终应用于基于各向异性超表面的两个透射偏振转换器的设计。