A wideband absorber working in the L- and S-bands based on magnetic materials

In this paper, a multi-layered microwave absorber that can work in the L- and S-bands is proposed. The absorber is composed of a traditional medium and magnetic material coatings. A genetic algorithm is used to achieve rapid design of a multi-layered absorber. The absorptivity of the absorber is more than 90% in 1.13–4.36 GHz under normal incidence, i.e., 117.7% fractional bandwidth. Moreover, the total thickness is 13 mm, corresponding to 0.049λ0 at the lowest operating frequency. Meanwhile, the absorber also has good wide-angle and polarization-independent characteristics. When the incident angle increases to 40°, it still can keep stable absorption in both TE and TM polarization modes. The working mechanism of the absorber is analyzed from the perspective of equivalent complex impedance, transmission line theory, and power loss density. Finally, a sample was fabricated and measured. The experimental results agree well with numerical simulations, achieving ultra-broadband and ultra-low frequency absorption.