In this article, a novel tunable attenuator based on graphene is proposed. It consists of a coupled microstrip line (CMSL) and two graphene-covered gaps in MSLs. By utilizing a biased voltage, the surface impedance of graphene can be tuned, and then, the reflective coefficient at two ports of the coupler can be correspondingly adjusted; therefore, the performance of the attenuator can be modified. The design procedure and the mechanism of the attenuator are demonstrated in detail. To verify the analysis, a prototype was fabricated and tested. According to the measured results, the fabricated attenuator presents the favorable attenuation tuning range from 3 to 20 dB at the operating frequency from 1 to 6 GHz, and it is just 38 mm $\times22$ mm in size. Besides, $\vert S_{11}\vert $ of the attenuator can always be maintained at a low level, and the phase of $S_{21}$ is substantially unchanged.

中文翻译：

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基于石墨烯耦合微带线的可调衰减器

在本文中，提出了一种基于石墨烯的新型可调衰减器。它由耦合微带线 (CMSL) 和 MSL 中的两个石墨烯覆盖的间隙组成。利用偏置电压可以调节石墨烯的表面阻抗，进而相应调整耦合器两个端口的反射系数；因此，可以修改衰减器的性能。详细展示了衰减器的设计过程和机制。为了验证分析，制造并测试了原型。根据测量结果，制作的衰减器在 1 至 6 GHz 的工作频率下呈现出 3 至 20 dB 的良好衰减调谐范围，并且仅为 38 mm $\times22$ 毫米大小。除了， $\vert S_{11}\vert $ 衰减器的相位可以始终保持在低电平，并且相位 $S_{21}$ 基本不变。