A thin ultra-wideband microwave absorbing structure printed on flexible substrate with resistive-ink made of multiwall carbon-nanotube

In this paper, we present a ultra-wideband radar absorbing structure operating in 5-50GHz frequency range. Two layer of Frequency Selective Surfaces (FSS) separated by dielectric spacer and having 160 Ω/sq. and 80 Ω/sq. respectively are printed on flexible PC-sheet with home-made water-based MWCNT-ink. For a thickness of 5mm a measured reflection coefficient bandwidth below -15dB is achieved over a bandwidth of 31GHz between 9-40GHz band, and agrees very well with simulation. The higher absorption bandwidth of absorber at normal incidence is benefitted from the stacked gradient of optimized surface resistance of resistive-FSS structure separated by below λ
_o
/4 spacer besides the bandwidth of the proposed absorber combines flexibility and compactness.