Ultra-wideband metamaterial absorber based on a hybrid structure of resistor-reinforced cross kite frame

A wideband metamaterial absorber with a thin layer remains a challenging task. An ultra-wideband metamaterial absorber based on a hybrid structure of a resistor-reinforced cross-shaped kite frame is proposed. The unit cell of the metamaterial absorber draws on the stability principle of traditional kites. A cross-shaped metal frame serves as the support and resistors reinforces at key connection points to maintain overall stability. The air between the dielectric substrate and the metal plate is filled with lightweight polymethacrylimide foam. The period of the unit cell is 15 mm, which is equivalent to 0.25λL, and the total thickness is 5.27 mm, which is equivalent to 0.088λL. When electromagnetic waves impinge on the structure, the metal framework captures the electromagnetic energy, and the loaded resistors convert it into heat through ohmic loss. Simulation and experiment results show that this kite-shaped design metamaterial absorber achieves over 90% broadband absorption in the frequency of 5–18 GHz, with a relative bandwidth of 113%, and has a good polarization angle and incidence angle insensitivity.