Broadband Microwave Absorption Properties of Ultrathin Composites Containing Edge-Split Square-Loop FSS Embedded in Magnetic Sheets

A convenient fabrication process about the ultrathin broadband composite microwave absorption material (MAM), which involves a frequency selective surface (FSS) sandwiched between two different magnetic sheets, is presented in this letter. The FSS consists of an array of elements with the geometry of square-loop having a split in each edge (denoted as edge-split square-loop FSS). The top and bottom magnetic sheets were prepared based on silicon rubber filled with sphere-shaped and flake-shaped carbonyl iron powders, respectively. It is revealed by measurement and simulation results that the composite MAM with the FSS that induces multiple resonances has a broad operating bandwidth compared to the traditional magnetic MAM without FSS. The low-frequency resonance can be manipulated by adjusting the size of the split S, while the high-frequency resonance is generally invariable. The composite MAM with the thickness of 2.2 mm has an operating bandwidth with the reflectivity below -10 dB in the frequency range of 4-18 GHz, which is nearly 2.7 times the bandwidth of the traditional magnetic MAM.