Improving Impedance Matching and Microwave Absorption Performance of Magnetic Microwave Absorbing Layer by Cutting Away Periodic Macro Elements

It has been increasingly hard to further decrease the permittivity of magnetic microwave absorbing layers (MALs) through micro- and meso-scale regulations of absorbents, limiting the improvement of impedance matching and microwave absorption performance. Here, macro-scale regulation of metamaterials is applied to push forward the performance improvement. The absorption band of the 1 mm and 2 mm thick carbonyl iron (CI)-based MALs here is 8.4 GHz to 13.6 GHz and 3.8 GHz to 6.6 GHz, respectively. A meta-MAL is obtained through cutting away periodic cylindrical macro elements from the 2 mm MAL. In this way, the permittivity is significantly reduced and the absorption band can be expanded to 7.7 GHz to 18 GHz. By comparing the meta-MAL to the MALs with equal thickness and surface density, respectively, it is evident that meta-MAL always has better impedance matching characteristics and wider bandwidth. A sample was fabricated and the measured result verifies the design. This work will push forward further studies on performance improvement of various magnetic MALs by cutting away periodic macro elements, which is suitable for mass production in practical applications.