Enhancement of absorption bandwidth of magnetic microwave absorbers via embedding metamaterials

Traditional microwave absorbers are typically made of ferrite powders and/or ferromagnetic metal powders and rely on ferromagnetic relaxation in the powders [1]. These absorbers can show strong absorption over a relatively wide frequency range if the thickness is sufficiently large, and for a given absorption level the frequency bandwidth usually decreases with a reduction in the thickness. One can also make microwave absorbers by using metamaterials that consist of metallic patterns on a back-grounded dielectric substrate. The perfect metamaterial absorber can achieve near unity absorption and can be easily adjusted by changing the structure parameters [2]. That brings a new way to improve the absorption property of the traditional magnetic absorber, especially in low frequency range under the condition of limited thickness.