High-performance transparent mmWave shielding films based on metasurface absorbers for automotive radar applications

As autonomous driving technologies become more prevalent, radar sensors can potentially interfere with the safety systems of surrounding vehicles. In this study, we introduce a transparent metasurface absorber (MA) with a shielding effectiveness (SE) of over 40 dB and absorption performance exceeding 90% within the 76–81 GHz range. The MA comprises a metal-mesh-shaped resonator layer, a ground layer, and a polyethylene terephthalate-based dielectric layer. The resonator layer comprises two disk-shaped patterns, each filled with an internal micromesh structure, with sizes of 1.4 mm and 0.8 mm, respectively. The ground layer is designed as a nanomesh structure covering the entire area to maximize SE. The impacts of aperture size in the mesh-shaped electrode patterns within the resonator and ground layers on the performance of the MA was evaluated. Results show that the frequency band and absorption rate are influenced by the aperture size of the resonator layer, while the optical transmittance and SE value are influenced by that of the ground layer. An absorption rate of over 90% is achieved in the 72.5–79.5 GHz frequency range, while simultaneously obtaining an SE of 45.1 dB and an optical transmittance of 84.9%. Furthermore, the frequency range is influenced by adjusting the thickness of the dielectric layer. By decreasing the dielectric layer thickness from 525 to 375 µ m, the >90% absorption range shifts to the 80.1–87.7 GHz frequency range. This innovative MA can significantly enhance the stability of autonomous driving and can be applied in several fields, such as electromagnetic shielding, stealth technology, energy harvesting, and mobile communications.