Experimental Validation of a Reconfigurable Coaxial Metasurface Radar Absorber Using Varactor Diode Tuning

The development of radar absorbing devices turned at the beginning of the millenium to metasurfaces. Reduced sizes, wide array of possible impedances, easy implementation of electronics are among the main benefits rendering them an adequate solution to the challenges of stealth. However, even these novel systems are intrinsically limited in their bandwidth. Fortunately, the recent interest for time-varying devices highlighted the possibily to overcome such limitations. To serve as a first step towards a functional time-modulated metasurface, this work focuses on the experimental validation of a reconfigurable metasurface absorber. Finite-element simulations and experimental measurements are compared to validate the behavior of the designed metasurface. Despite slight discrepancies, seemingly originating from an inaccurate varactor diode model and unexpected additional resistivity, the experimental results highlight a very good reconfigurability of the metasurface in terms of frequency agility.