Analysis and enhancement of the bandwidth of ultrathin absorbers based on high-impedance surfaces

A design for ultrathin absorbers with wideband absorption is presented. The absorber is composed of a high-impedance surface comprising a lossy patch array over an electrically thin grounded dielectric substrate. This class of absorbers is usually considered as a narrowband structure. Here, we show that the performance of this absorber can be considered as the low-frequency case of a λ/4-thick absorber and wideband absorption can be actually achieved by the use of multi-resonance arrays. Arrays with different resonant geometries are proposed to design dual-band and triple-band ultrathin absorbers. By tuning these absorption bands closer to each other, we obtain a wideband absorber without increasing the thickness, and the experimental verification is also presented.