Abstract
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.
Keywords: Graphene, absorption coefficient, loss tangent, permittivity, permeability, reflection coefficient.
Graphical Abstract
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