▎ 摘　　要

Flexible and tunable radar absorbers (RAs) are in great demand both in stealth technologies and electromagnetic delusion for concealment of complex targets such as aircraft and unmanned aerial vehicle from radar detection. As a general approach, conventional lumped components such as varactor diodes and resistors are employed to achieve frequency and/or amplitude tunability of RAs. However, despite the intricate feeding networks and complex fabrication processes, this approach shows great difficulty in integrating the conventional rigid components with flexible substrate. Hence, it is an enormous challenge to realize both dual-tunable and flexible RAs. Here the authors for the first time design and experimentally characterize a flexible and dual-tunable RA with independent control of the frequency and amplitude. Most important is that the achieving both amplitude and frequency control is fully based on the tunability of graphene, without any lumped devices and intricate feeding network, and even without any metal involved. Hence, this dual-tunable RA shows the priority of being flexible, light weight, and environmentally friendly. Although the prototype in this work is operating in microwave spectrum, the tunable functionalities at millimeter or terahertz spectral bands can also be obtained due to the intrinsic tunability of graphene.