image: The orthogonal and semi-auto-focusing distribution patterns are respectively implemented on the lateral and rear windshields to address diverse in-cabin scenarios.
Credit: Shanwen Luo, ©Science China Press
In future intelligent connected vehicles, the demand for high-speed data transmission among passengers is growing rapidly. However, complex electromagnetic environment inside vehicles such as occlusion from metal body frames, seats, headrests, and other interior components often leads to severe attenuation of the wireless signals, which has become a limiting factor for communication quality. Recently, a research team from the State Key Laboratory of Millimeter Waves at Southeast University and National Key Laboratory of Microwave Photonics at Nanjing University of Aeronautics and Astronautics published an innovative study in National Science Review. The research demonstrates how a functionally adaptive transparent metasurface integrated into the car windows can enable obstacle-avoiding and self-recovering signal transmissions via ingeniously designed “Weber beams.”
When wireless signals propagate inside a vehicle cabin, they are often blocked by the physical obstacles, creating “blind zones.” To address this challenge, the research team turned their attention to a special type of “non-diffracting beam.” Among these, Weber beams possess unique “self-accelerating” properties, allowing them to propagate along curved paths and thus bypass the obstacles in their way. Additionally, they exhibit the “self-healing” capabilities: even when blocked, the beam can be reconverged behind the obstacle and restored its original waveform and energy.
The smart window developed by the team uses low-cost, easily processable flexible PET substrate and precise printed circuit board (PCB) fabrication techniques. Its core advantage lies in combining excellent electromagnetic control capability with high optical transparency. Experimental data show that the metasurface sample achieves a visible light transmittance of 73.5%, which meets the industry standards for modern automotive windshields without interfering with the passenger visibility.
In real-vehicle tests, the researchers integrated the specially designed metasurfaces into the side and rear windows. The results show that, even under extreme conditions with significant physical occlusion, the system can dynamically reconstruct signal transmission paths. Compared with the traditional Gaussian beams, the 5G signal guided by this smart window showed an average increase of 8.37 dB in received power, enabling the real-time transmissions of high-fidelity full-color images.
This study integrates a non-diffracting wavefront control mechanism into the transparent media, offering a practical new approach to overcoming signal transmission limitations in enclosed spaces. The solution not only significantly improves in-vehicle communication quality in complex occluded environments, but also lays a foundation for the application of transparent electromagnetic functional surfaces in broader scenarios. The potential applications include smart building glass facades, transparent monitoring interfaces for industrial IoT, and biomedical optics-microwave fusion sensing, among others.