The Car Headlights Are Becoming Radar Sensors
Fraunhofer researchers are working on a thin-film system with which radar waves can be controlled with low losses. It is almost transparent in the visible range and even forms high-frequency waves.
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The installation space for radar sensors on a automotive is strongly limited. The use of radar technology has become an essential part of the technology. There is a wide range of systems for adaptive speed control, lane change support, collision avoidance and pedestrian and cyclist detection that pave the way towards autonomous driving.
To overcome the problem of limited installation space, researchers at the Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, together with partners in the "RadarGlass" project, have developed radar sensors that can be integrated into the front headlights of a car.
To Control Radar Waves With Low Loss
By integrating the radar sensors into the headlights of a vehicle, they are protected from snow, ice and rain and the outer vehicle shell is not affected. Designers of future generations of cars are not restricted in their creativity by additional sensor installations on the vehicle. In collaboration with their project partners, scientists from the Fraunhofer FEP 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 specifically shaped and directed.
The coating can modify the beam spreading in different ways 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.
Thin-Film System in the Visible Range Almost Transparent
Dr. Manuela Junghähnel, project manager at the Fraunhofer FEP, comments: "Within the framework of the project, we have developed a thin-film system that is almost transparent in the visible range and can also form 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 and 120 °C".
The demonstrator is designed for long-range use: it allows the radar to be focused with a gain of 20 dBi (antenna gain) in a small beam width of 5° in the direction of travel. Obstacles at a distance of up to 300 m can be detected. 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 involved in the so called 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 frequency band from 76 to 81 GHz. Thus the suitability and performance of the radar reflector could be determined.