Recent progress in angle-insensitive narrowband and broadband metamaterial absorbers

Recent progress in angle-insensitive narrowband and broadband metamaterial absorbers is presented herein. Initially, a few narrowband structures are described along with their absorption mechanisms. A bandwidth-enhanced absorber, conceptually derived from the existing narrowband geometry, is also discussed. Finally, several broadband absorbers having wide absorption bandwidths across different microwave frequency ranges are illustrated. The reported structures are primarily designed to exhibit high angularly stable responses suitable for practical applications. Furthermore, their geometries are fourfold symmetric, thereby displaying polarization-independent characteristics. Experimental verifications of the designed absorbers have been confirmed under normal and oblique incidences. The angle insensitivity, polarization independence, flexible absorption bandwidths (from narrowband to broadband), and commercial feasibility of the reported structures might establish them as potential candidates for manifold absorber applications