A high-efficiency, ultra-wideband absorber with wide-angle stability

In this work, we propose a high-efficiency, ultra-wideband absorber with wide-angle stability in the microwave regime. The designed absorber consists of copper octagonal split-rings with chip resistors and an air spacer. Benefiting from good impedance matching, the absorption exceeds 90% in the ultra-wide waveband from 10.1 to 29.2 GHz under the wide incident angle of 45°. The equivalent circuit model (ECM) of the proposed absorber is developed to explain the mechanism of ultra-wideband absorption. Furthermore, the absorption strength and bandwidth of the proposed absorber could be tuned by adjusting the resistances of the chip resistors. Finally, the absorber samples are fabricated in experiments, and the measured absorption spectra agree well with the simulated ones, which validates the effective design of an absorber. The proposed absorber has the advantages of high efficiency, ultra-wide bandwidth, and wide-angle stability, which are highly desirable for dynamic radar cross section reduction.