Ultrawideband microwave metamaterial absorber with excellent absorption performance and high optical transparency based on double-layer mesh structures

Achieving microwave absorbers that combine wideband and excellent absorption performance with high optical transparency remains a significant challenge in the field of radar stealth. In this paper, an ultrawideband metamaterial absorber consisting of double-layer mesh structures and two transparent dielectric layers is proposed. In the absorption layer, an indium tin oxide (ITO) mesh pattern, equivalent to an <i>RL</i> circuit (series connection of resistance <i>R</i> and inductance <i>L</i>) to reduce design complexity, enhances the optical transparency of the absorber when combined with a mesh structure in the shielding layer. The polycarbonate (PC) cover plate is innovatively introduced to adjust the impedance matching, improving the absorbing bandwidth and angular stability. Based on the equivalent circuit model (ECM), optimization of the circuit parameters for the designed unit cell is conducted with the genetic algorithm (GA) and exhibits excellent absorption performance. Simulation and experiment results show that the reflection coefficient of the sample fabricated by the laser etching process is below -20 dB from 7.78 GHz to 12.58 GHz, covering the whole X band and reaching a relative bandwidth of 47.2%. Moreover, the average optical transmittance of the designed absorber is fixed at 81% in the visible region of 400-700 nm. The proposed metamaterial absorber with excellent absorption performance and high optical transparency provides a new avenue for the research and development of stealth and electromagnetic compatibility (EMC).