Thin ultra-wideband metamaterial absorber with switchable reflection/transmission band and polarization insensitivity

In this paper, a thin ultra-wideband metamaterial absorber is presented based on frequency selective surfaces (FSSs), magnetic material, and PIN diodes. The proposed absorber consists of a lossy layer and a switchable layer. The upper lossy layer adopts a sandwich structure combining magnetic material and FSS. PIN diodes are embedded on the FSS to form the bottom switchable layer. Through controlling the biasing states of the diodes, the absorber can actively switch between the reflection and transmission states at S band, achieving over 85% absorption efficiency in the ultra-wideband of 5.15-18 GHz. Notably, the absorber exhibits a thin thickness (3.9 mm) and good polarization insensitivity. This constructed metamaterial absorber can achieve camouflage and bandpass by synergizing passive ultra-wideband absorption with active switchability, showing potential for microwave absorption, wireless communications, adaptive microwave systems, and electromagnetic countermeasures in the future.