A wideband multilayer filter with frequency tunable characteristics is proposed using active frequency selective surface (AFSS). The proposed AFSS includes three metal layers, while the top and bottom metal layers are embedded with varactors. The metal layers are separated by dielectric layers. By simultaneously adjusting the bias voltage loaded on both ends of the varactor diode, the working bandwidth of the AFSS can be continuously tuned. The operating mechanism is studied using an equivalent circuit, which is composed of an LC series resonance circuit and a parallel resonance circuit. The simulation results prove that the proposed AFSS performs wideband filtering in the frequency range of 3.55 to 4.43 GHz without a bias voltage. With a bias voltage of −19 V, the AFSS working passband is tuned to 4.43 to 5.53 GHz. Simulation and experimental results show that the AFSS has wideband filtering characteristics and good tunable performance.

中文翻译：

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一种使用有源频率选择表面的宽带多层可调滤波器

提出了一种使用有源频率选择表面（AFSS）的具有频率可调特性的宽带多层滤波器。提议的 AFSS 包括三个金属层，而顶部和底部金属层嵌入了变容二极管。金属层由介电层隔开。通过同时调整加载在变容二极管两端的偏置电压，AFSS 的工作带宽可以连续调谐。采用等效电路研究其运行机理，等效电路由LC串联谐振电路和并联谐振电路组成。仿真结果证明，所提出的 AFSS 在 3.55 至 4.43 GHz 的频率范围内执行宽带滤波，无需偏置电压。在 -19 V 的偏置电压下，AFSS 工作通带调谐到 4.43 至 5.53 GHz。