Frequency-tunable metamaterial absorber with three bands

Abstract

We propose a three-band metamaterial absorber composed of two opposite-trapezoid rings with only one varactor diode. By changing the reverse bias voltage on the varactor diode from 0 V to −15 V, the frequencies at the first and second absorption peaks can be dynamically tuned from 2.77 GHz to 4.36 GHz and 8.11 GHz to 8.41 GHz, respectively. With the increase of the reverse bias voltage, the frequency shift of the first absorption peak may reach 1.59 GHz with the absorptivity from 68.4% to 99.8%; for the second absorption peak, the frequency shift reaches 0.30 GHz with the absorptivity of above 97.4%; while the third absorption peak hardly shifts keeping nearly perfect absorptivity of above 99.9%. The absorption mechanism is analyzed by surface current distributions and the simulation results are verified by the experimental measurement. The proposed metamaterial absorber may be useful in the fields of multi-band electromagnetic stealth, biosensors, reflectors and so on.