A Dynamically Tunable Microwave Absorber Based on Graphene

In this article, a dynamically tunable graphene-based absorber in Ku-band is proposed for the first time, the center frequency of which can be continuously tuned while maintaining an excellent absorption performance. It consists of a periodically patterned graphene sandwich structure (GSS) and periodic patches printed on the substrate backed with the ground. The periodically patterned GSS is directly deposited on the top surface of patches. By using the external bias voltage, the proposed absorber can provide a dynamically tunable operating frequency from 13.9 to 16.4 GHz, in which the absorptions remain above 0.92. To theoretically investigate the performance of the absorber, an equivalent circuit based on transmission-line is derived. We fabricate and measure some samples to experimentally verify the dynamical frequency tunability of the graphene-based absorber, which has never been really achieved before in microwave frequency. A good agreement between simulation and measurement is acquired. The whole thickness of the absorber is equal to 0.06 lambda, which provides a path forward for the realization of a dynamically tunable and ultra thin absorber. The design strategy can generally be applied to other wavelength region applications such as mechanical deformation and bolometric detector.