Wideband Microwave Absorber with Dynamically Tunable Absorption Based on Graphene and Random Metasurface

A wideband microwave absorber with dynamically tunable absorption is proposed in this paper. It consists of a few layers of large-area graphene and a layer of random metasurface. Through the superimposition of a few layers of graphene, the tunable range of graphene sheet resistance is lowered to 80 Ω/sq - 380 Ω/sq, which is more suitable as the resistance film of broadband microwave absorber, because it is easier to match the impendence of free space. In addition, by choosing twelve proper elements of metasurface and distributing them randomly, more resonance frequencies and phase responses can be achieved, thus improving the bandwidth of the microwave absorber and reducing its profile simultaneously. By tuning the sheet resistance of graphene via bias voltage, the absorbance of proposed absorber can be tuned from 80% to 50% in a wide bandwidth from 5 GHz to 31 GHz. The prototype of proposed absorber is fabricated and measured. The reasonable agreement between the simulated and measured results verifies the accuracy of our approach.