Flexible and Dual‐Tunable Radar Absorber Enabled by Graphene

Abstract

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.

Multifunctional Graphene Metasurface for Highly Flexible Control of Microwave Absorption

“…34 Geng et al introduced an approach for achieving the flexible and tunable radar absorber by utilizing a patterned GSS instead of an active metasurface; the amplitude and frequency of the absorption can be dynamically tuned through a static bias configuration applied to graphene. 35 However, the above-mentioned multifunctional absorbers are limited to achieving reconfigurable absorption bands in narrow-band absorption mode or broadband absorption mode. To date, very few published articles reported multifunctional reconfigurable absorbers that can not only achieve broadband electromagnetic absorption performance but also switch to narrowband absorption modes and further adjust their absorption amplitude in each of the above operation modes.…”

“…Although full-polarization and multifunctional absorbers can be constructed by designing a symmetrical structure, this solution requires the use of more lumped elements, which means higher costs and more complex processes . Geng et al introduced an approach for achieving the flexible and tunable radar absorber by utilizing a patterned GSS instead of an active metasurface; the amplitude and frequency of the absorption can be dynamically tuned through a static bias configuration applied to graphene . However, the above-mentioned multifunctional absorbers are limited to achieving reconfigurable absorption bands in narrow-band absorption mode or broadband absorption mode.…”

Design of a wideband and tunable radar absorber

“…When voltage was supplied to the multi-layer graphene in a radar absorber created by A G D'Aloia [27], the absorber's reflectance might be as low as −10 dB from 7 to 22 GHz. A flexible radar absorber composed of continuous graphene sandwich structure and patterned graphene sandwich structure was created by Mingyang Geng, whose amplitude and frequency all could be dynamically tuned via applying bias voltages on the graphene from 9 GHz~11.5 GHz [28].…”

“…The thickness of the graphene capacitor is neglected due to its thinness. Increasing the voltage applied to the graphene capacitor can lead to a reduction in the surface resistance of graphene and an increase in its conductivity [20,28]. Consequently, we employ the variation in the surface resistance to investigate the impact of the applied voltage on the graphene capacitor on radar absorption performance.…”

Coupling Controlled Dual‐Band Tunable Electromagnetic Extraordinary Transmission in Graphene Hybrid Metasurfaces

“…In photonics and optoelectronics, the properties of graphene can be tuned by electrostatic field, magnetic field, chemical doping, and optical pumping for wide-range tunability in a broad frequency range. [35][36][37][38][39][40][41][42][43][44][45][46][47][48][49] There have been scientific advances in graphene-based metasurfaces or metamaterials, especially in the terahertz and optical domain. [50][51][52] Also some progresses have also been made for lower frequency applications with large-scale graphene in, e.g., dynamical absorption, polarizer, and programmable metasurfaces.…”