Headlamp glass cover doubles as radar antenna

Headlamp glass cover doubles as radar antenna

Technology News |
By Christoph Hammerschmidt

In the RadarGlass joint project, the Fraunhofer Institute for Laser Technology ILT from Aachen, the Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP from Dresden and the Institute for High Frequency Technology IHF of RWTH Aachen University are working together. The researchers have developed a layer system that enables the integration of radar sensors into car headlights. “It’s the perfect position because they cover the near and far range completely and also allow a view to the side,” explains Patrick Gretzki, scientist in the Micro- and Nanostructuring Group at Fraunhofer ILT. Another advantage is the heat generated by the headlights, which ensures that the sensors are always free of ice and snow in adverse weather conditions and thus have an undisturbed view of the surroundings.

The project is investigating which thin-film system can be used to control radar waves with low losses without restricting the lighting task of the headlamp. The three institutes cover all the necessary competencies – from the development of a suitable coating system to the design of high-frequency components and precise production using laser radiation.

Radar sensor, integrated into the
glass of the headlamp. (C) Fraunhofer ILT

Together, they developed a functional, electrically conductive thin film for the inside of the headlamp cover that can be used to shape and direct the radar beam in a targeted manner. The layer can manipulate the beam differently depending on the type of application: In order to detect and recognize pedestrians, the radar beam is directed to the side, for example. Like a human eye, the beam can also be focused on the near or far range.

In order to direct and shape the radar beam, small elements of the coating must be precisely structured so that they can act as antennas for the radar waves. The Fraunhofer ILT has developed a laser process to generate the antenna elements. Experience in this field has already been gained in a preliminary study on the structuring of thermal glazing. This normally blocks RF waves such as WiFi or mobile radio networks. After laser processing, the glass could be made selectively permeable for certain frequencies.

With a resolution of up to 10µm, the laser-manufactured structures are much more precise than those produced using conventional printing processes. Alternative methods such as lithography are limited to flat or slightly curved surfaces and cannot be used for the complex 3D surfaces of headlight covers. In addition, this requires a complex process chain. Two obstacles that are overcome by the new laser-based machining process.

With the aid of simulations, the RadarGlass partners are developing structures for the targeted manipulation of radar waves in the 77 GHz range. Demonstrators are used to confirm and further develop the functionality of the technology. “With the demonstrators, we are proving that we can simulate, design and produce the antennas in such a way that they fulfill the desired properties,” explains Gretzki. “We are currently presenting the solution to industry representatives so that we can then proceed with further recycling steps. In the next phase of the project, we will install the solution in a real headlamp.”


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