Reliable Qualification of Automibile Radars

© Fraunhofer FHR
ATRIUM: Demonstrator zum Nachweis des Hardware-Funktionsprinzips.
© Fraunhofer FHR
Künstlerische Darstellung des Radarzielsimulators ATRIUM.

ATRIUM (automotive test environment for radar in-the-loop testing and measurements) is a radar target simulator in the E-band currently being developed by Fraunhofer to facilitate the extensive control of the functionality of the next generation of automotive radar sensors. In contrast to conventional radar target simulators, ATRIUM will be able to fully simulate critical traffic scenarios.

Due to the varied utilization possibilities (private transport, freight transport) and numerous advantages (enhanced driving comfort, greater economic benefits), autonomous driving is one of the most promising technologies of the future. Special attention must, however, be dedicated to the safety of autonomous driving to protect road users from unnecessary dangers and increase social acceptance for this technology. This also applies to the functional efficiency of currently available driver assistance systems which already perform important safety-relevant functions in automobiles. In particular, the reliability of automotive radar sensors must be guaranteed as these constitute an important component of such driver assistance systems and are also destined to play an important role in future automobile generations. This calls for a test environment which allows the extensive qualification of automotive radar sensors.

With its radar target simulator ATRIUM, Fraunhofer FHR is currently implementing a corresponding test environment for the E-band. This will facilitate the realistic simulation of traffic scenarios through the synthesis of an electromagnetic wave field, whereby the target simulator will be able to place virtual radar targets in any required position. Moreover, the movement of radar targets can be simulated through continuous position changes as well as through Doppler shift. In addition, the system will be capable of recreating complex target signatures, whereby radar targets from radar sensors will not only be perceived as points but rather as diverse objects comprising several components (e.g. rear, bumper, wheels). This functionality facilitates the simulation of traffic scenarios in which the reliable functioning of automotive radar sensors makes a decisive contribution to traffic safety.

The target simulator takes the form of a test stand which is positioned in front of a test vehicle that is equipped with radar sensors. This paves the way for the testing of mounted automotive radar sensors and facilitates the consideration of three central aspects:

1. New radar technologies and sensor concepts can be tested regardless of the weather conditions and with high repeating accuracy without disregarding the influence of the vehicle body

2. Long-term use of a vehicle or damage to the vehicle can have a negative impact on the functionality of radar sensors. Effects such as these can be measured and characterized on the test stand.

3. The test stand is designed for a high throughput of automotive radar sensors and can therefore be used by technical inspection organizations within the framework of routine inspections.

The virtual positioning of radar targets along various space dimensions is possible through the utilization of two different technologies. Along down-range, i.e. in the direction of travel, the signal transmitted by the automotive radar sensor is received, modified and retransmitted by repeaters as shown in Fig. 2. The FPGA-based repeater allows the generation of Doppler and time-shifted as well as amplitude and phase-varied copies of the transmit signal. Through this modification, the signal can also be temporally delayed, whereby the radar targets can be shifted along the down-range. Depending on the operating mode, it is also capable of reacting to any required or known input signals in a targeted manner.

The utilization of several repeaters, with spatially arranged transmit and receive antennas, also allows the positioning of radar targets along the cross-range, i.e. orthogonal to the direction of travel. This requires a suitable antenna configuration and coordinated controlling of the repeaters. Spatially arranged array antennas are used for this purpose. The design of the repeaters and the antenna arrangement are being optimized within the framework of the project.

In this way, ATRIUM will promote the qualification of radar-based driver assistance systems and make an important contribution to the safety of all road users today and in the future.