Flexible design and realization of wideband microwave absorber with double-layered resistor loaded FSS

A flexible design of a wideband double-layer microwave absorber is proposed. In order to break through the limitation of single-layer absorbers at finite resonant frequencies, a special double-layered structure is adopted. The middle layer functional frequency selective surface is the core of the double-layer absorber. It exhibits two functions, which are resonant or lossy in a low frequency and strong reflective in a high frequency. As a result, the coupling between the two layers is weak, and this feature leads to the absorber having two different absorption bands which are provided by two single-layer absorbers (named as functional layers (FLs)), respectively. It means that an engineer could target the design for a particular band according to requirements without degrading the performance on the other band. For the flexible design, two FLs, a dual-band absorption precursor and a continuous absorption modified absorber are proposed successively. During the whole design process, all structures are fabricated and measured. The measurement result shows that the reflection of the modified absorber below -10 dB covers a bandwidth of 2.98-16.62 GHz in normal incidence. The good agreement between simulation and measurement validates the proposed absorber.