# Fingerprints of the Automotive Radar Scattering of Passenger Cars and Vans
## 3 Results and Discussion
### Scattering Characteristics of Different Vehicle Types
For the Sprinter, the detections were spread over almost the entire bounding box and most detections came with high RCS values between \(-10\) dBsm and \(+10\) dBsm. A high concentration of detections with RCS values up to 15 dBsm was located at the right side of the vehicle at \(x~{}=~{}2.3\) m. This backscatter was presumably caused by the side of a metal plate, which is used as a footstep to facilitate the entrance to the vehicle. Figure 8: Spatial detection distribution and RCS distribution for the different vehicle types. The white rectangles illustrate the target bounding box. In a further evaluation step, the number of recorded target detections for the vehicles was analyzed (Table 2). For each car, the measurement data from ten recorded repetitions were accumulated, resulting in a total number of more than 3000 recorded measurement cycles. The number of target detections varied between 5527 and 14,731, resulting in remarkable differences for the arithmetic mean number of target detections per measurement cycle: The values for the S-Class and GLS were very similar (2.36 and 2.22), but only 1.78 detections per measurement cycle were detected on average for the EQE. Therefore, the question arises as to whether this is related to the powertrain. On the other hand, the light duty vehicles G-Glass, V-Class and Sprinter generated considerably more detections per measurement cycle (3.13, 3.75 and 4.87, respectively). The standard deviation for the number of detections from individual measurement runs was between 0.08 and 0.26. Therefore, the deviations between single repetitions were smaller than the differences between different vehicle types. For a more detailed analysis, the arithmetic mean number of detections was calculated around fixed distances \(R\), which are illustrated in Figure 9. In general, the number of target detections increased for shorter distances. For all vehicles except the Sprinter, the number of target detections rose from 1...2 detections at \(R=100\) m up to 4...5 detections at \(R=20\) m. For the Sprinter, 2.8 target detections per cycle were already recorded at \(R=100\) m and the number of detections rose up to 6.3 detections per measurement cycle at \(R=20\) m. This observation is associated with the significantly longer length of 5.9 m, while the length of all other vehicles falls in the range between 4.9 m and 5.2 m (Table 1). However, the curves display distinct differences: The types S-Class and the GLS (blue and green curve) reveal very similar behavior, while only one target detection was received above a distance of \(R=50\) m for the EQE (purple curve). For smaller distances, the increase in the number of detections behaved similarly to the S-Class and the GLS. For both, the G-Class (yellow curve) and the V-Class (orange curve), the number of target detections increased more rapidly than for the three previous vehicle types. While the numbers of detections from both vehicles were similar for distances between \(R=70\) m and \(R=100\) m, the number of detections for the V-Class were 28% higher compared to the G-Class for shorter distances. For the Sprinter (red curve), the number of target detections was the highest across all distances. Apparently, the different ground clearances and vehicle underbodies caused diverse backscatter intensities (RCS values) of the received radar signal. Therefore, the distance at which the radar sensor is capable of detecting underbody reflections varied, resulting in different point cloud sizes at different distances.