A thin and flexible multispectral single-layer FSS (MSLF) absorber is presented using a micro-holed, macroscale FSS combined with an IR absorbing ground. The FSSs are simplified to MSLF by changing the absorbing layered microstructure to a transmitting microstructure. Dual band millimeter waves (MMWs) are absorbed by the macroscale resonance cavity, while the target IR waves are absorbed by the IR absorbing ground after penetrating the micro-hole array pattern. Thermal emission is reduced significantly due to its low emissivity at IR bands other than the target IR. It is confirmed analytically and experimentally that patterns of various sizes do not exhibit functional crosstalk. The demonstrated multispectral absorption and low thermal emission make this a very promising material for IR-MMW selective bi-stealth. Furthermore, the proposed structure can be applied to existing macroscale patterns in order to increase their applicability by providing additional selectivity without any functional interference.

In this study, optically transparent and single-layer frequency selective surface (FSS) (OTSF) absorber for dual-band millimeter-wave (MMW) absorption and low IR emissivity is proposed. By adopting indium tin oxide (ITO) and polyethylene terephthalate (PET), the proposed OTSF absorber has great optical transparency. The OTSF absorber exhibits high absorption at dual-band frequency in millimeter-wave range. In IR band, the OTSF absorber exhibits low average band emissivity for mid-wave infrared (3‒8 μm) band and long-wave infrared band (8‒15 μm. Thermal images of the OTSF absorber clearly show its low emission characteristics similar with that of metal. Our proposed OTSF absorber structure has great promise in practical application of MMW-IR multispectral stealth materials.