Ultra-broadband microwave absorption by ultra-thin metamaterial with stepped structure induced multi-resonances

Since the electromagnetic (EM) absorbers have wide uses in many military and civilian applications, much effort has been devoted continuously to broadening the absorption bandwidth while making the thickness as thin as possible. In this paper, we present an ultra-wideband metamaterial absorber composed of periodic stepped-structures of magnetic material with a mixture of carbonyl iron powder and resin. The proposed metamaterial absorber features an ultra-thin thickness of only 0.025 wavelength and an ultra-broad operating bandwidth (defined by absorption larger than 90%) from 1.23 to 19 GHz. The ultra-broadband strong absorption is mainly attributed to the giant magnetic loss of the magnetic material, the structure-induced multi-resonances, and the edge diffraction effects of the stepped structures. In addition, good angular performance is observed for all polarizations. Experiments are carried out and are in good agreements with the simulated ones. We also propose a method to further reduce the weight of the structure without affecting much of the overall absorbing performance. The proposed metamaterial absorber has promising prospects in many real-world applications, such as RCS reduction and EM compatibility.