Simultaneous Rain Detection and Inter-vehicle Distance Estimation Using a Single FMCW Automotive Radar

This paper presents a novel method for simultaneous inter-vehicle distance estimation and rainfall detection using a single 60 GHz FMCW radar. The proposed system enables accurate ranging and environmental sensing without the need for additional sensors. A trihedral corner reflector and a metallic vehicle body were used as targets to evaluate signal attenuation and distance estimation under various rainfall conditions. Experimental results confirmed that, at a distance of 3.4 m, the received power decreased by approximately 5 $$%$$ and 2.5 $$%$$ for rainfall intensities of 30 mm/h and 15 mm/h, respectively. The theoretical model based on ITU-R P.838-3 showed strong agreement with measured attenuation, validating the feasibility of rainfall estimation from radar signal amplitude. Moreover, the ranging error remained within ±0.09 m, demonstrating high robustness of distance estimation even in adverse weather conditions. The proposed approach highlights the potential of millimeter-wave radar to function as both a distance and environmental sensor, paving the way for next-generation intelligent transportation systems and weather-adaptive autonomous vehicles.