Metasurface based Ultra-Thin and Flexible Multi-Frequency Perfect Absorber in Microwave Regime

An ultra-thin and flexible multi-frequency perfect absorber based on metasurface in microwave regime is proposed and analyzed. The absorbing device is composed of a thin conductive film combined with an in-phase all-reflecting metal-dielectric-metal cavity, from which nearly perfect absorption can be implemented due to coherent cancellation of the electromagnetic wave inside the conductive film. Detailed characteristics of the absorption on the structural parameters including both thicknesses of the layered structure and arrangement of the metasurface patterns of the device are investigated and analyzed. Simultaneous multiple frequency absorption using a single device is proposed and implemented using multiple nested metasurface patterns, from which a 3-frequency microwave perfect absorber is obtained and optimized with a total thickness of only ~0.2 mm in the frequency range of 6 GHz -10 GHz. The proposed method provides a possible way of implementing an ultrathin and flexible microwave absorber which is of great importance in practical applications.