In this letter, a paradigm for designing tunable frequency selective surfaces (FSSs) with angular stability is presented. The tunable FSS is implemented by nonresonant subwavelength unit cells loaded with varactor diodes, which can be applied in a dynamic and efficient compensation mechanism. The red shifts introduced by varactor diodes are used to compensate the deviation under oblique incident angles. The proposed tunable FSS is a two-layer structure composed of an array of wire grid and an array of split square ring loaded two varactor diodes. The periodicity of one split square ring is same with that of 2 × 2 wire grids. The equivalent circuit based synthesis method is analyzed to investigate the underlying principle of the proposed FSS. The experimental measurement is carried out in C-band frequency, which demonstrates the feasibility of this method. The measured results are in good agreement with the simulations, manifesting the angular stability at 4.25 GHz.

中文翻译：

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具有角稳定性的可调谐频率选择表面

在这封信中，介绍了设计具有角稳定性的可调频率选择表面 (FSS) 的范例。可调 FSS 由加载有变容二极管的非谐振亚波长单位单元实现，可应用于动态和高效的补偿机制。变容二极管引入的红移用于补偿斜入射角下的偏差。所提出的可调 FSS 是一个两层结构，由一个线栅阵列和一个加载了两个变容二极管的分裂方环阵列组成。一个分裂方环的周期与2×2线栅的周期相同。分析了基于等效电路的综合方法，以研究所提出的 FSS 的基本原理。实验测量在C波段频率下进行，这证明了这种方法的可行性。测量结果与仿真结果吻合良好，表明在 4.25 GHz 时具有角稳定性。