An ideal placement for radar sensors would logically be the front headlights. By integrating the sensors into the headlights of a vehicle, they are protected against snow, ice and rain. In addition, the sensor would not affect the outer vehicle shell; designers of future generations of cars would not be restricted in their creativity by additional sensor installations on the vehicle. In the RadarGlass project, scientists from the Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP and their project partners first investigated which thin-film system can be used to control radar waves with low loss without restricting the lighting task of the headlamp. For this purpose, a thin transparent functional coating was developed for an assembly mounted in the headlamp, with which the radar beams can be shaped and steered in a targeted manner. The coating can manipulate the beam propagation differently depending on the type of application: In order to detect and recognise pedestrians, for example, the radar beams are deflected to the side. Like an eye, the beam shape can be adjusted to the near or far range. In order to direct and shape the propagation of the radar beams, small areas of the coating must be precisely structured by laser so that they can act as antennas for the radar waves.
In the course of the project, the scientists created a thin-film system that is almost transparent in the visible range and can also shape high-frequency waves. The manufacturing process has been optimised to such an extent that the coating leaves the colour of the light source unchanged and withstands temperature fluctuations between -30 °C and +120 °C, explains project manager Dr. Manuela Junghähnel.
One demonstrator is designed for long-range use: it allows the radar to be bundled with an antenna gain of 20 dBi in a focused beam width of 5°. The range of the radar is 300 metres.
In addition to the Fraunhofer FEP, the Institute for High Frequency Technology at RWTH Aachen University and the Fraunhofer Institute for Laser Technology ILT are also involved in the RadarGlass project. Experts from the Institute for High Frequency Technology at RWTH Aachen University simulated the antenna layout and checked it by measurements in the 76 GHz – 81 GHz band. Thus the suitability and performance of the radar reflector could be determined. The researchers at the Fraunhofer ILT developed a high-precision laser ablation process to structure the antenna elements on the coating.
The “RadarGlass” project has opened up many potential applications in the automotive and automotive supply industry, and the researchers expect a wide range of impulses to continue to come from the current development trend towards autonomous vehicles. In addition to licensing agreements, further cooperation projects with industry are being sought in order to implement the radar sensors in series production.
Fraunhofer-Institut für Lasertechnik ILT: www.ilt.fraunhofer
Institute for High Frequency Technology at RWTH Aachen University www.ihf.rwth-aachen.de
Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP: https://www.fep.fraunhofer.de/en.html