# Multi-Frequency Target Detection Techniques for DVB-T Based Passive Radar Sensors
## 5 Experimental Results for Aerial Surveillance Application
### Test Campaign and Data Collection  
We report the results obtained against the data collected during the test campaigns that were carried out in November 2015 at the Leonardo S.p.A. premises, in Rome. The acquisition geometry is depicted in Figure 5. The reference antenna was steered toward the DVB-T transmitter of Monte Cavo (about 22.5 km away) while two surveillance antennas were adopted, pointed at 270\({}^{\circ}\) clockwise from north. Specifically, Yagi-Uda antennas were employed yielding a main beam width of about 36\({}^{\circ}\). Therefore the main beam of the surveillance antennas included a section of the civilian air traffic departing or arriving to the Fiumicino and Ciampino airports. The corresponding aircrafts are used in the following as targets of opportunity to test the proposed MF detection techniques based on the available ATC registrations. During the test campaign, seven different data sets have been collected. Each data set is composed by sequential data files of temporal duration equal to 1.2 s, spaced by about 4 or 5 s. The total number of data files and the total time duration of each data set is reported in Table 1. In the considered test campaign, the signals for 4 DVB-T channels within the UHF band have been simultaneously collected, all emitted by the same transmitter at the following carrier frequencies: 586 MHz, 714 MHz, 762 MHz, and 634 MHz. Specifically, among all the available digital television channels, we have selected those characterized by high power levels (79 KW, 100 KW, 35 KW and 79 KW, respectively) and that, based on a rough analysis, had the best performance for PR purposes. First of all, in order to evaluate the performance of each DVB-T channel, all the available data files of each carrier frequency have been separately processed according to a basic DVB-T PR processing scheme described in Section 2. In particular, the ECA [24] is applied with 1000 taps (i.e., 33 km @ _f_s = 64/7 MHz). A CPI of 0.3 s is used to evaluate the CAF maps that span a surveillance area of 100 km \(\times\) 300 m/s. Target detection is performed by resorting to a CA-CFAR threshold with a probability of false alarm equal to \(P_{fa}=10^{-3}\). In detail, a region of \(N_{R}=19\) cells in \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Dataset \#** & **1** & **2** & **3** & **4** & **5** & **6** & **7** \\ \hline N\({}^{\circ}\) of data files & 178 & 142 & 305 & 409 & 329 & 320 & 327 \\ \hline Total Time duration [min] & 12 & 10 & 26 & 27 & 22 & 21 & 22 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Details of the datasets collected during the performed test campaign. Figure 5: Sketch of the acquisition geometry in the case of aerial surveillance application. range and \(N_{V}~{}=~{}5\) cells in velocity around the cell under test has been employed to estimate the disturbance, resulting in Q = 86 secondary cells also taking into account a guard interval of \(N_{r}=N_{v}=3\) cells in range and velocity, respectively. Finally, a 2 out of 2 criterion is adopted to integrate the detection results obtained at the two surveillance channels allowing a nominal \(P_{fa}=10^{-6}\) on the final range-velocity plane. As an example, Figure 6a,b show the detection results obtained for the first data set (Dataset #1) with the DVB-T channels transmitted at 714 MHz and 634 MHz, respectively. Notice that the reported frequency channels represent the best and the worst channels in terms of detection capability based on a SF operation. In detail, all the detection results within the total acquisition time (12 min) have been reported. In particular, in each figure, the grey dots represent the raw detections of the PR sensor while in red is reported the available air truth for direct comparison. Specifically, a gray scale has been employed to plot the raw detections obtained on successive scans (i.e., the gray tone used progressively gets darker for more recent plots).