A Conformal Metamaterial-Based Optically Transparent Microwave Absorber With High Angular Stability

We put forward an optically transparent microwave absorber based on a conformal broadband metamaterial, which shows high angular stability. Our absorber is a double-layer sandwich structure mainly made of transparent polyvinyl chloride sheets and indium tin oxide films. To achieve wideband absorption and high angular stability, an impedance layer composed of square spiral elements is exploited to increase the absorption bandwidth. A compensation layer is then employed to address the mismatch between the impedance of the absorber and that of free space at high angular incidences. Experimental results show that a high light transmittance (69.4%), together with an adequate absorption bandwidth (85.7%) and angular stability (60 degrees) may be achieved with planar and conformal configurations, including different curvatures.