Transparent Microwave Absorber Based on Patterned Graphene: Design, Measurement, and Enhancement

A patterned graphene-based transparent microwave absorber is proposed in this paper. Graphene is transferred onto polyethylene terephthalate (PET) film, and patterned as μm-level periodic patches, so that a capacitive and resistive graphene surface is obtained at microwave band. By placing this graphene/PET film on the top of a glass substrate and applying fluorine-doped tin oxide film as the reflective layer, transparent absorber working at Ku band is realized. The optical transmittance of the fabricated graphene/PET film reaches around 80% in the whole optical light range, while the absorption coefficient reaches 90% at 12.6 GHz. By analyzing the parasitic effects in the rectangular waveguide measurement, a good agreement is obtained among the measurement, three-dimensional full-wave simulation, and the equivalent circuit. Two configurations are further analyzed to enhance the absorption level and the working bandwidth of the absorber. 100% absorption and 3 GHz bandwidth broadening are realized.