A frequency and bandwidth tunable metamaterial absorber in x-band

Smart control is an attracting and important function for modern electromagnetic wave absorber. This paper presents the design, fabrication, and measurement of a frequency and bandwidth tunable metamaterial absorber (MA) in X-band. The unit cell of the MA consists of a microstrip resonator loaded with the varactors. Simulation and measurement results show that by tuning the bias voltage on the varactors, the peak absorption frequency can be tuned by 0.44 GHz with the peak absorption greater than 95%. Field and circuit model analysis is conducted to reveal the working mode and predict the absorbing frequency. After that, by specially designing the bias circuit so as to adjust the bias voltage on neighboring unit cells separately, dual resonance and absorption peaks occur, and the overall absorption bandwidth can thus be tuned conveniently by controlling the difference of the two resonance frequencies. The center absorbing frequency can also be tuned. Simulation and experiment results show that the 75% absorption (-6 dB reflection) bandwidth can be tuned from 0.40 GHz to 0.74 GHz, which is a two-fold tuning range. This work is believed to improve the state-of-the-art smart metamaterial absorber. (C) 2015 AIP Publishing LLC.