Imidazole ionic liquid based ultra-broadband low-thickness metamaterial absorber from union-pyramid-like structure design

In this work, a union-pyramid-like imidazole ionic liquid metamaterial absorber (UPL ILMMA) is developed. The UPL ILMMA achieves over 90% absorption across 7.08–50.00 GHz, with a relative absorption bandwidth of 150%. When the incidence angle is 55°, the absorption exceeds 90% in the range 7.83–50.00 GHz (TE) and 9.47–50.00 GHz (TM). Due to the excellent thermal stability of IL, the UPL ILMMA still maintain excellent absorption performance in the temperature range of 25–100 °C. In addition, the UPL ILMMA exhibits polarization insensitivity and low thickness (6.1 mm). The high absorption efficiency is attributed to the synergistic impedance matching and electromagnetic energy dissipation that are enhanced by the UPL structure design. The experimental results confirmed over 90% absorption in the ultra-broadband ranges of 7.75–40.00 GHz (TE) and 7.40–40.00 GHz (TM). Under 55° oblique incidence, over 90% absorption is maintained in both polarization modes, with absorption bandwidth spanning 11.01–40.00 GHz (TE) and 6.81–40.00 GHz (TM). These combined advantages position UPL ILMMA as a promising candidate for next-generation broadband absorbers in electromagnetic shielding, stealth technology, and microwave engineering applications.