Design of an Ultra-thin Tunable Metamaterial Absorber for Broadband Frequency Applications

A novel broadband metamaterial absorber (MMA) is presented in this paper. The absorber is a single layer structure based on the topology of a high impedance surface (HIS), but in which the conventional top layer is replaced by an active frequency selective surface (AFSS) loading with resistors and varactor diodes. The absorbing resonant frequency of the MMA changes by adjusting the capacitance of varactor. Simulated results show that the absorption of the absorber covers a broadband of 2.35 GHz-11.45 GHz above 98% when the capacitance increases from 0.1 pF to 5 pF. At the same time, the total thickness of this absorber, 2 mm, is only λ/64 of the lower limit frequency.