Coating boosts WiFi reception through walls
Researchers at TU Wien in Vienna and the University of Rennes in France have developed a technique to create coatings that boost the transmission of radio waves for better WiFi reception.
该方法允许计算量身定制的抗反射结构，该结构可以添加到仅在无线信号中部分渗透的墙壁，以便可以通过墙壁传导整个信号而无需反射。
到目前为止，在理论上还不清楚这种事情是可能的。研究团队能够为此提供一种计算方法，并在实验中成功测试了它：微波是通过复杂，无序的障碍物迷宫发送的，然后计算了匹配的抗反射结构并将其放置在障碍物前面。本实验。可以使反射几乎完全消失：没有任何波浪返回到它们被注入的侧面。
A similar approach has been taken to block sound waves:Cutting noise with a lightweight metamaterial sound screen
“You can think of it as being similar to the anti-reflective coating on your pair of glasses,” says Prof. Stefan Rotter from the Institute of Theoretical Physics at TU Wien. “You add an extra layer to the surface of the glasses, which then causes light waves to pass better to your eyes than before – the reflection is reduced.”
This is more difficult with a disordered medium in which a wave is repeatedly scattered and deflected until it finds its way out of such a maze via complicated paths such as a concrete wall. The waves are scattered at many points so that only a part of them gets through, the rest is reflected or absorbed in the wall.
“First, you simply have to send certain waves through the medium and measure exactly in which way these waves are reflected by the material,” said Michael Horodynski at TU Wien. “We were able to show that this information can be used to calculate a corresponding compensating structure for any medium that scatters waves in a complex way, so that the combination of both media allows waves to pass through completely. The key to this is a mathematical method that we developed to calculate the exact shape of this anti-reflective layer.”
The experiment in Rennes saw microwaves sent through a metallic waveguide in which the waves are scattered by dozens of small objects made of metal and Teflon placed completely randomly and in a disorderly manner. Only about half of the microwave radiation reaches the other side, the rest were reflected.
After precisely measuring the scattering behaviour of this system, it was possible to use the newly developed method to calculate which additional scattering points form a perfect “anti-reflective layer” for exactly this random system.
对于击中抗反射结构的任何波形，这为100％的传输提供了可忽略的反射。
This compensation for wave scattering with additional scattering can be used for other applications such as imaging in biophysics. Wave dynamics and wave scattering will also play a major role in 6G, the next generation of mobile communications after 5G.
www.tuwien.at;doi：10.1038/s41586-022-04843-6
