Multispectral flexible ultrawideband metamaterial absorbers for radar stealth and visible light transparency

The existing metamaterial absorber cannot simultaneously achieve wide bandwidth, light thickness, flexibility, and transparency in the radar frequency band. To address that problem, a flexible transparent and ultra-broadband metamaterial absorber is designed, fabricated, and tested in the present study. The metamaterial absorber is built as a sandwich structure with an indium tin oxide (ITO) top layer surface resonance unit, an air dielectric layer, and an ITO grounding layer. The absorptivity of the metamaterial absorber exceeds 90% in the frequency range of 3.7–102 GHz, and it can effectively cover the S, C, X, Ku, K, Ka, U, V, and W bands of the radar working band. The absorptivity exceeds 80% when the incident angle changes in the range of 0–45° under TE polarized mode and exceeds 90% when the incident angle changes in the range of 0–60° under TM polarized mode, which indicates that the metamaterial absorber has good incident angle stability and insensitive to polarization. Moreover, radar stealth properties in the 2–40 GHz frequency band are verified after measuring. The light transmittance of the metamaterial absorber exceeds 80%, ensuring that the solar cell array and aircraft window receive light normally. Furthermore, the thickness of the metamaterial absorber is merely 1.02 mm, which has good flexibility and can perfectly fit the object's surface. These excellent performances demonstrate that the metamaterial absorber has wide application potential in the fields of radar stealth and micro satellite stealth.