A ultra-wideband thin microwave absorber using inkjet-printed frequency-selective surfaces combining carbon nanotubes and magnetic nanoparticles

A ultra-wideband microwave absorber (UWMA) combining frequency-selective surfaces (FSS) and dielectric layers is proposed. FSS patterns are printed by inkjet on dielectric layers using a resistive magnetic ink made of suspended carbon nanotubes decorated with ${\text{Fe}}_3{\text{O}}_4$ nanoparticles. The UWMA exhibits a huge fractional bandwidth of 140%, corresponding to reflectivity lower than − 10 dB and absorption higher than 90%, observed from 7 GHz to 43 GHz, meaning a 36 GHz bandwidth, for a thickness of only 0.26 $\lambda$. This performance is achieved through a proper selection of FSS surface resistance, tuned by the number of printed layers. Excellent agreement is observed between designed and measured low reflectivity and high absorption.