## 6 Validation in Real PR Trials
### PR Trials Results  
Acquisitions in both validation scenarios were carried out at a central frequency of 11.3 GHz, covering three DVB-S channels horizontally polarized, as shown in Figure 14. The signals were filtered digitally, to eliminate the noise at frequencies where there is no  
Figure 12: RCS simulation model and estimated BRCS in each range bin for the two trial scenarios in the two possible trajectories along the roads: moving away from the PR or approaching it. Figure 13: Curves of coverage ranges versus target BRCS for the measured antenna gain. System sensitivity equals\(-148.5\) dBm calculated for \(P_{D}=80\%\) and \(P_{FA}=10^{-4}\) (\(SNR_{DET}=16\) dB). DVB-S channel and an Extensive Cancellation Algorithm (ECA) [20] was employed to mitigate the Direct Path Interference (DPI), improving the target detection. The coherent processing interval (CPI) was fixed to 200 ms which produced a set of 75 RD maps from each measurement of 15 s.  
The deployment in scenario 1 for the first trials with the reflectarray antenna was performed on the 10 th of February of 2021. From all the measurements carried out, one is selected in which there were two cooperative targets: one of them moved away from the PR and the other started at the end of the road and moved towards the PR. Besides those, there were two more cars in the street at that moment, one in each direction. Figure 15 shows the RD map together with the GPS ground truth of cooperative targets for CPI 59. Figure 16a shows the cumulative of the maxima from all the 75 RD maps, each of them normalized by its pedestal noise level, and the GPS ground truth during all the acquisition. The conversion of GPS data to Range-Doppler is not precise when the target is accelerating, because a small error in sample time gives a great difference in the Doppler shift (\(f_{D}\)) due to the high operation frequency. Some targets, probably bigger than cars, can be detected crossing the round at the end of the street, at range bin around 220. Figure 16a can be compared with the results published in [4] in which a commercial dish antenna of 40 cm diameter was employed for the surveillance channel in the same scenario (Figure 16b). Comparing the results of a car moving away in both cases, a great improvement with the reflectarray antenna can be observed, as the signal to interference ratio for the same kind of targets in range bins between 50 and 100 has increased considerably. Table 2 shows the quantitative comparison, in terms of the probability of detection \(P_{D}\) and maximum detected range bin, for both acquisition in same scenario with reflectarray and parabolic dish as surveillance antennas, employing the same CA-CFAR detector configured for a desired probability of false alarm \(P_{fa}=10^{-4}\), and a tracker stage based on the Kalman filter. \(P_{D}\) is estimated as the ratio between true detections over the tracker-estimated positions. Analysing the case of a car moving away, the maximum detection range in the case of reflectarray is limited by the end of acquisition time, i.e., last CPI of acquisition contains  
Figure 14: Spectrum of the signal acquired by the reference channel in one of the measurements of the trials. Figure 15: RD map of CPI 59 for validation of the designed reflectarray in scenario 1.  
a detection. In the case of the parabolic dish antenna, the maximum range bin where a detection is associated with the track is 144, but from range bin 58, the density of detections associated with the track is low, which explains the decrease in \(P_{D}\). The deployment in scenario 2 was performed on the 2 nd of March of 2021. In this scenario, there is usually a lot of traffic, so a controlled target was not employed.