Ultra-broadband cross-pyramid ionic liquid metamaterial absorber with 60° angular stability

In this work, a metamaterial absorber based on a cross-pyramid structure employing ionic liquid (IL) was designed. Numerical simulations show that the absorber achieves over 90% absorption across 7.37-50.00 GHz, with a relative absorption bandwidth of 149%. Its symmetric design ensures polarization insensitivity from 0° to 90°. Even at 60° incidence, it maintains over 90% absorption in 7.90-50.00 GHz (TE) and 11.35-50.00 GHz (TM). Owing to the thermal stability of the IL, performance remains stable between 25 °C and 100 °C. The efficient electromagnetic wave absorption is attributed to the synergistic effect of a 3D and multilayer impedance-gradient structure and the highly lossy IL material. Experimental results confirm over 90% absorption in 8.16-40.00 GHz (TE) and 8.17-40.00 GHz (TM), with wide bandwidths maintained even at 60° incidence. These features make the absorber promising for electromagnetic shielding, stealth, and microwave applications.