Achieving ultra-broadband thin microwave absorber by synthesizing all-dielectric and metal-based metamaterials

Metamaterial absorbers (MMAs) have been widely investigated in recent years. The synthesis of traditional metal-based MMAs and new-kind all-dielectric MMAs has great potential in improving absorption performances, which has not yet been unlocked. Here, the two kinds of MMAs are properly designed and synthesized to realize ultra-broadband absorption with small thickness and light weight. The metal-based structure consists of periodic circular metal patches, while the all-dielectric structure consists of a magnetic sheet with periodic cylindrical holes cut away. The total thickness of this hybrid MMA is only 4.1 mm, and the weight of magnetic composites can be reduced by 15.2%. The simulation result shows that −10 dB absorption band can be achieved in 3.7–18 GHz, with two absorption peaks at 5 and 15.5 GHz, respectively. The first peak is mainly attributed to the all-dielectric structure that offers high flexibility in regulating equivalent electromagnetic (EM) parameters. The second peak is attributed to the cooperation of the two structures. Specifically, the metal-based structure acts as an impedance matching layer, while the all-dielectric structure acts as a lossy layer. A sample was fabricated, and the measurement result agrees well with the simulation result. This work will push forward further studies on absorption performance improvement by synthesizing all-dielectric and metal-based MMAs, which is beneficial to practical applications.