Tunable triple-band millimeter-wave absorbing metasurface based on nematic liquid crystal

We propose and design a tunable triple-band millimeter-wave absorbing metasurface based on nematic liquid crystal (NLC). Numerical results based on both effective circuit model and full-wave simulations verify the triple-band absorption property. All triple absorption peaks can be shifted by changing the bias voltage applied to the nematic liquid crystal. We fabricate and measure a triple-band absorbing metasurface sample, which covers 100 × 100 mm2 and is composed of 20 × 20 unit cells. In experiments, when no bias voltage is applied to the NLC layer, the resonant frequencies of the absorbing metasurface are 25.4, 28.7, and 32.8 GHz, respectively. When a 5-V bias voltage is applied, all the absorbing peaks redshift, and a frequency tunability range of 9.5%, 9.1%, and 8.58% is observed in three resonant frequencies, respectively. The experimental results are in good agreement with the numerical simulations. The proposed tunable absorbing metasurface provides a way forward for the realization of tunable millimeter-wave metasurface devices that can be applied in multi-band detection and imaging.