Radar has been part of everyday life for many years on airplanes or on the high seas, and radar is also being used more and more often in “close range” cars. The enormous advances in semiconductor technology in recent years now allow a further step in miniaturization. For this purpose, researchers at the Karlsruhe Institute of Technology (KIT), in cooperation with the Fraunhofer Institute for Applied Solid State Physics (IAF) in Freiburg and the industrial partner VEGA Grieshaber KG, are developing ultra-compact radar sensors that are modular and excellent for the diverse requirements of industrial sensor technology are suitable.
A previously unattained resolution can be achieved with the radar sensors, in which the integration of antennas on chips or in the chip housing can also be implemented due to the small wavelength. However, opening up the frequency range above 100 GHz has so far been made more difficult by extremely complex assembly and connection technology, which for a long time represented a limitation on the way to inexpensive integrated modules.
Variants from the “Real100G.RF” project of the German Research Foundation (DFG) are now being brought together with circuits from Fraunhofer IAF. A scalable miniature radar front end is developed from this, which is then evaluated for industrial usability in cooperation with the company VEGA from Schiltach in the Black Forest.
The project “Scalable THz miniature radar for industrial applications” (SATIRE) is one of six trilateral projects funded by the DFG and the Fraunhofer Society (FhG). The aim is to transfer scientific knowledge into business. In the trilateral SATIRE project, companies can participate in research innovations at an early stage.
"The KIT is a nationwide unique institution and covers an extraordinary range of research fields, the focus in addition to research and teaching is always on innovations and thus on the cooperation between science and industry, which complement and enrich one another", says Theresia Bauer, the Baden-Württemberg Minister for Science, Research and the Arts. “I am therefore very happy about the funding of the KIT transfer project by the DFG and the Fraunhofer Society. This is where future-oriented research comes into play. The funding shows once again the importance of our universities and research institutions in Baden-Württemberg, even across national borders. "
Focus on miniaturization
As part of the SATIRE project, a scalable, highly integrated 300 GHz radar sensor with a bandwidth of over 50 GHz and thus a resolution in the millimeter range is to be created. The modules with a maximum size of 10 mm x 10 mm x 7 mm, including the lens, can be connected to a control board to form a MIMO system ("Multiple Input Multiple Output", a method for using several transmitting and receiving antennas for wireless communication) and used individually. This makes the modules particularly suitable for the diverse requirements of industrial sensors. "The project also uses the technological possibilities offered by the Microelectronics Germany Research Laboratory at KIT," says the President of KIT, Professor Holger Hanselka. “As a third pillar alongside research and teaching, innovation at KIT stands for the application-oriented character of research and development activities. This innovation activity again builds a bridge between knowledge and application."
Radar sensors at frequencies above 100 GHz have enormous potential as a supplement to existing optical sensors, whether cameras or lidar. “On the one hand, they allow good resolution and, at the same time, high robustness, for example against smoke or dust,” explains Professor Thomas Zwick, project manager and head of the Institute for High Frequency Technology and Electronics (IHE) at KIT. To achieve a resolution in the millimeter range, the circuit must have an output bandwidth of at least 50 GHz with a transmitter that can be switched off for TDM-MIMO operation ("Time Division Multiplex", method of signal transmission). For this purpose, lenses made of ceramic and plastic are tested, 3D printing and injection molding are used. The entire component will be the same size as the lens, ie have dimensions of a maximum of 10 mm. "With our mini radar, we are not only improving the measurement performance, but also the industrial feasibility," says Zwick. The small size and the precise measurement open up completely new fields of application. In addition, the architecture with multipliers and an external local oscillator as well as a transmitter that can be switched off allows several radar sensors to be interconnected on a circuit board to form a MIMO radar.
The result is a versatile radar front end that can be scaled to different systems and is essential for industrial applications, as a large number of applications have to be served here. The strong practical relevance is a characteristic of the project, in which companies are given the opportunity to participate in innovations from research at an early stage - in this case VEGA.