Adaptive Broadband Radar Absorber Based on Tunable Graphene

An innovative broadband adaptive absorber, providing a reflection coefficient lower than-10\, dBin the frequency range from 7 to 22 GHz, is proposed. The new absorber is a two-period dielectric Salisbury, in which the outer lossy sheet is made of a graphene monolayer, and the inner one consists of a tunable graphene/dielectric laminate (GL). The two dielectric spacers are made of a commercial low-loss polymer. The total thickness is~ 6\, mm. The adaptive broadband response of the absorber is achieved tuning the effective sheet resistance of the GL through an applied electrostatic field bias. The sensitivity analysis of the reflection coefficient of the absorber illuminated by a plane wave with normal incidence is carried out with respect to the spacer thickness and the graphene carrier charge mobility. By applying a dc-voltage source always below 15 V, the minimum reflection coefficient of the adaptive absorber is centered around 14 GHz, and it is characterized by a bandwidth at-10\, dBof~ 15\, GHz.