Detecting Vulnerable Road Users Utilizing the Harmonic RCS of Active Tags at 79/158 GHz

Vulnerable road users have not been able to benefit equally from the improved traffic safety supported by automotive sensors. In 2020 this culminated in traffic fatality highs of more than 30-years for pedestrians, motor, and pedal cyclists. Regarding radar sensors, vulnerable road users suffer from a lower RCS compared to other vehicles like cars and busses. Accordingly, their detection is more challenging, especially while being surrounded by those vehicles, as is common in city traffic. Therefore we have presented a harmonic radar system which allows for tag based detection inside of a seperate receive channel. In this work we present fundamental and harmonic RCS measurements of a bicycle equipped with the tag, to allow for the comparison to other approaches. While its fundamental RCS is exceeded by large metal objects, the harmonic RCS increases with range, as long as the tag is saturated. Thanks to the clutter-free receive channel, even a relatively small level, which is determined by the tag's saturated output power, is sufficient for detection.

Automated summary

Vulnerable road users, such as pedestrians, motorcyclists, and cyclists, have not benefited equally from the improved traffic safety provided by automotive sensors. In 2020, there was a significant increase in traffic fatalities for these groups. Compared to cars and buses, vulnerable road users have a lower RCS, making their detection more challenging, especially in congested city traffic. To address this issue, a harmonic radar system has been presented, which allows for tag-based detection in a separate receive channel. The system has been tested with a bicycle equipped with a tag, and the results show that even with a relatively small level of tag output power, detection is possible thanks to the clutter-free receive channel.