# Experimental Evaluation of a MIMO Radar Performance for ADAS Application
## 3 Results
### Effective Probability of False Alarm  
In the first scenario with real targets, there are three pedestrians moving in different directions and at different distances in front of the radar. All of them describe straight trajectories at approximately constant speeds. The captured scenes were also taken on video. To evaluate the error made in the processing of the different echoes, a most probable instantaneous trajectory is estimated with a constant speed, or constant in sections, for the target. The echoes are inspected one by one, selecting those that most likely come from the target under study. In this type of analysis, there is always an intrinsic uncertainty since it is not possible to know if an echo comes from the target that is being specifically tracked, from a nearby target, or if it is a false target generated by noise. Faced with this, the only practical procedure is to track with an appreciable number of echoes along the probable instantaneous trajectory, as we have tried to do in this study. Figure 3 shows the trajectory of the three targets in this first scenario, with all the echoes selected by the analysis program. As stated, the selection of speeds was carried out with a value \(\mathit{PFA}_{\mathit{ref}}=0.2\), while the result in the figure is the one corresponding to the value \(\mathit{PFA}_{\mathit{range}}=0.05\). The radar is located at the origin of the coordinates. The figure shows the echoes that most likely belong to one of the targets, located along the path of each pedestrian. There are also false targets, some of them generated by noise peaks or coming from echoes affected by noise, so that their position has been incorrectly estimated. Some of the echoes would fall into the doubtful category, as those framed with a solid blue line, since the observer or a subsequent echo evaluation system could consider them valid, assigning them to a particular pedestrian. It is worth noting that to perform the  
Figure 2: Measurements of a turning reflector on the calibration grid points. Red circles are the reference points. The darker blue points correspond to correctly measured echoes, the lighter blue points correspond to incorrectly located echoes or false echoes. task of classifying an echo as valid, doubtful, or clearly erroneous, it is not enough to simply look at the final echo map shown in the figure. To make this classification, it is necessary to track it in time during the course of the experiment so that the position of the received echoes can be compared with the real or estimated instantaneous position of each real target. The second scenario was composed by two pedestrians and a motorbike, describing straight paths and also the return of all three to their initial positions. As in the first case, the raw data obtained from the radar were analyzed again using \(PFA_{vel}=0.2\), for a first selection of targets, in velocity, and with several values, increasingly small, for the parameter \(PFA_{range}\). Figure 4 shows the global set of echoes received from the radar during this experiment. Figure 4: Echoes received over time in the second experiment (little blue boxes), with two pedestrians going and coming along approximately the same path and a motorcycle, describe the longest and most vertical paths. Arrows indicates the direction of the movement. Figure 3: Global map of the received echoes along the time in scenario 1, while three pedestrians are walking along straight paths. False or dubious echoes are enclosed with dashed or continuous blue lines. In the particular map of Figure 4, a larger number of echoes, valid and false, can be seen in comparison with the first scene. This is because a very low-demand PFA has been used, but also because the duration of the scene is longer. Finally, the third scene is a motorbike describing rounds in front of the radar with an approximate constant speed.