Background: Advancement in wireless communication technology has raised today’s living standards but has consequently led to the problems of electromagnetic (EM) air pollution as well as spectrum congestion particularly in radio frequency band. To overcome the traffic congestion problem in lower bands, terahertz frequency bands are explored but EM pollution still persists as a global issue, which can be addressed by a tunable microwave absorber. At THz frequencies, 2-D nanostructured graphene has been observed to be less lossy than using other materials and further finds its most interesting applications on account of the plasmonic mode supported by graphene resulting in extreme device miniaturization. At micro and mm-waves, graphene is resistive, hence it can be electronically controlled, ensuring its suitability for the design of tunable microwave absorber.

Objective: Designing of a frequency reconfigurable or frequency tunable absorber is the prime objective of the current work. Two-dimensional graphene absorber has been proposed here having inherent bandgap tunability property, which means the electromagnetic properties of graphene can be controlled via varying external bias potential.

Methods: The numerical modelling of graphene microwave absorber utilizing bulk graphene backed by glass and perfect electric conductor layer is reported in this paper. Finite element Method (FEM) based high frequency structure simulator (HFSS) platform is used to simulate the graphene absorber model. The whole structure is placed into a rectangular waveguide with two ports for absorber excitation.

Results: The variation of electromagnetic properties of graphene absorber is achieved by changing bias potential and further the absorption tunability for the designed absorber is investigated in the range from 2 GHz to 18 GHz. From reflection coefficient curves, it is authenticated that -72.6 dB reflection coefficient dip is obtained at 14 GHz for 5 volt bias potential, which shifts to higher side of frequency as the potential changes from 5 volts to 25 volts.

Conclusion: The results show that by increasing bias potential, absorption coefficient shifts to higher frequency and proves to be a tunable wideband absorber whose resonant frequency can be changed from one value to another without changing thickness or material properties of absorber, thus it can effectively incorporate with antenna substrate or surface of radar.

背景：无线通信技术的进步提高了当今的生活水平，但因此导致了电磁（EM）空气污染以及频谱拥塞（特别是在无线电频带中）的问题。为了克服较低频段的交通拥堵问题，已探索了太赫兹频段，但电磁污染仍然是一个全球性问题，可以通过可调微波吸收器解决。在THz频率下，已观察到2-D纳米结构的石墨烯的损耗要小于使用其他材料的损耗，并且由于石墨烯支持的等离振子模式导致了设备的极度小型化，因此它的应用最受关注。在微波和毫米波中，石墨烯具有电阻性，因此可以对其进行电子控制，

目标：设计可重构频率或可调谐频率的吸收器是当前工作的主要目标。此处提出了具有固有的带隙可调性的二维石墨烯吸收剂，这意味着可以通过改变外部偏置电势来控制石墨烯的电磁特性。

方法：本文报道了利用玻璃支撑的石墨烯和完美的导电层对石墨烯微波吸收器的数值模拟。基于有限元方法（FEM）的高频结构仿真器（HFSS）平台用于模拟石墨烯吸收器模型。整个结构放置在带有两个端口的矩形波导中，以吸收吸收剂。

结果：通过改变偏置电位来实现石墨烯吸收剂电磁特性的变化，并进一步研究了设计吸收剂在2 GHz至18 GHz范围内的吸收可调性。从反射系数曲线可以证实，在14 GHz下对于5伏偏置电势可获得-72.6 dB反射系数下降，随着电势从5伏变为25伏，该反射系数下降到频率的较高侧。

结论：结果表明，通过增加偏置电势，吸收系数会移至更高的频率，并被证明是一种可调谐宽带吸收器，其谐振频率可以从一个值更改为另一个值，而不会改变吸收器的厚度或材料特性，因此可以有效地吸收天线基板或雷达表面。