Temperature tunable ultra-wideband absorber based on ionic liquid

Abstract In this paper, a temperature tunable ultra-wideband absorber based on ionic liquid is proposed for the microwave frequency band. The absorber consists of a band-resistive frequency selective surface, a 3D resin cavity vessel, and an ionic liquid ([EMIm][N(CN) 2 ]) layer. Numerical simulation analysis shows that the absorptivity is more than 90% and a relative bandwidth is 113.04% in the range of 7.5–27 GHz. Meanwhile, the absorber absorptivity has different tuning effects in different frequency bands with the change of temperature. Along with the temperature going up, the absorptivity decreases in the low-frequency band of 6.5–14 GHz, the absorptivity increases in the high-frequency band of 28 GHz–40 GHz. It is worth mentioning that the proposed ionic liquid-based absorber has the characteristics of wide incidence angle and polarization insensitivity. Finally, the temperature tunable absorber model based on ionic liquid is fabricated by 3D printing technology. The experimental results are consistent with the simulation results, demonstrating that the absorber is practically feasible. In summary, the absorber achieves a wide frequency tuning range, which gives it great potential application prospects in fields such as frequency-selective thermal radiators.