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In this communication, a broadband and tunable radar absorber is proposed by integrating graphene capacitor with resistive frequency-selective surfaces (RFSS). The microwave reflectivity can be dynamically controlled by changing the effective sheet resistance of graphene through an electrostatic field bias. The simulated results indicate that this structure can tune its reflectivity over a wide frequency band ranging from 2.9 to 15.9 GHz under the normal incidence, when the graphene resistance is varied from 120 to 700 Ω/sq. The tuning range of the average reflectivity is from -4.6 to -15.3 dB. The physical mechanism of this tunable absorber is discussed by studying the electric field distribution and power loss density. We fabricated this absorber and measured its tunable reflectivity by applying different biasing voltages. The experimental results are in a good agreement with those of the simulation results. In addition, this absorber is also verified to have a good angular stability and polarization insensitivity, which will have broad prospects in the application of stealth technology.
Song et al. (Tue,) studied this question.