An Ultrathin Frequency Selective Rasorber Based on Electromagnetic Composite Absorption

In this article, an ultrathin frequency selective rasorber (FSR) based on electromagnetic composite absorption is proposed. At first, a subwavelength unit (SLU) for electromagnetic composite absorption is designed and its mechanism is discussed under the excitation of electric field ( $E$ -field) and magnetic field ( $H$ -field) of incident electromagnetic waves separately. Next, a single layer ultrathin frequency selective absorber (UFSA) is constructed by eight SLUs, which are arranged by mirror symmetry and 90° rotation symmetry. Then, two UFSAs are designed, which work at different frequencies. The proposed ultrathin FSR, which is constructed by simply stacking two UFSAs, has a transmission band (2.09–2.69 GHz) and two absorption bands (two absorptive peaks above 90% at 2.05 and 2.78 GHz) on both sides of the transmission band. Importantly, compared to the traditional FSR, the profile of the FSR is low and $0.039\lambda _{c}$ . Finally, to verify the design and analysis, the proposed FSR was fabricated and measured. A good agreement between the results of the experiment and simulation can be obtained accordingly.