# Multi-Frequency Target Detection Techniques for DVB-T Based Passive Radar Sensors
## 6 Experimental Results for a Maritime Surveillance Application  
The benefits resulting from the application of MF approaches for maritime surveillance are investigated with reference to an acquisition campaign that was carried out in a site located on a small Italian island. The DVB-T PR receiver has been installed very close to the coast with the surveillance antennas pointed toward the open sea to allow the detection of the typical maritime traffic travelling during the day. The reference antenna was steered toward a DVB-T transmitter located about 170 km away. Only a single data set composed by 93 data files is considered in the following for this experimental campaign; each data file is about 1.2 s of duration with a temporal spacing of 12 s \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & **CEN-MF-2** & **CEN-MF-3** & **CEN-MF-4** & **CEN-MF-5** & **CEN-MF-6** & **CEN-MF-7** & **CEN-MF-8** & **CEN-MF-9** & **CEN-MF-10** \\ \hline
**SF 1** (586 MHz) & 84 & 30 & 172 & 136 & 332 & 47 & 260 & 1061 & 1.06\(\cdot 10^{-5}\) \\
**SF 2** (714 MHz) & 90 & 40 & 179 & 139 & 352 & 54 & 274 & 1128 & 4.59\(\cdot 10^{-6}\) \\
**SF 3** (762 MHz) & 66 & 31 & 128 & 111 & 275 & 38 & 203 & 852 & 6.52\(\cdot 10^{-6}\) \\
**SF 4** (634 MHz) & 48 & 21 & 98 & 100 & 219 & 36 & 180 & 702 & 5.63\(\cdot 10^{-6}\) \\ \hline
**DEC-MF-24** & **111** & **41** & **200** & **163** & **402** & **59** & **332** & **1308** & **5.00\(\cdot 10^{-6}\)** \\ \hline
**CEN-MF-2** (**SF 1-2**) & 111 & **42** & 215 & 173 & 425 & 63 & 335 & 1364 & 5.29\(\cdot 10^{-6}\) \\
**CEN-MF-3** (**SF 1-3**) & **121** & **43** & **225** & **184** & **434** & **67** & **356** & **1430** & **3.68\(\cdot 10^{-6}\)** \\
**CEN-MF-4** & 120 & **44** & **224** & **178** & **437** & **68** & **368** & **1439** & **3.93\(\cdot 10^{-6}\)** \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Synthesis of the detection results obtained against all the available Data Sets for an aerial surveillance scenario. between two consecutive files. Therefore, a total acquisition time of 19 min is available. Four DVB-T channels have been simultaneously collected at the following carrier frequencies: 682 MHz, 634 MHz, 626 MHz and 546 MHz. Although only the results for a single dataset are reported, we observe that many targets of opportunity were present in the surveyed area up to bistatic range of 210 kilometers so that the detection capability provided by different signal processing scheme can be reasonably compared. To this end Figure 8a,b show the detection results (grey dots) on the range-velocity plane for the best and the worst frequency channel, respectively. Again, a gray scale associated to the scan number has been used for the detections of the PR sensor. In this case, the ECA [24] is applied with 1000 taps and a CPI of 1.2 s is employed to evaluate the CAF maps over an area of 220 km \(\times\) 20 m/s. Then a CA-CFAR with \(P_{fa}=10^{-4}\) have been adopted (where Q and the guard interval are the same that have been defined previously) and a 2 out 2 detection criterion across the two available surveillance antennas has been applied to reduce the number of false alarms (namely \(P_{fa}=10^{-8}\)). In each figure, all the plots whose velocity in module was less than 1 m/s have been discarded to obtain much clearer outputs. The red tracks in Figure 8a,b identify the maritime traffic as provided by the Automatic Identification System (AIS) registrations. Figure 8: Detection results over the range-velocity plane using single DVB-T channels representing the best and the worst cases, respectively: (**a**) channel at 626 MHz; (**b**) channel at 546 MHz. As is apparent, with both the considered single channels, the system is able to detect many targets also at very long bistatic ranges (see for example the vessel labeled \"Fourni\" at about 200 km or \"Capitan Markos NL\" at 210 km). In fact, the conceived sensor was shown to provide OTH capabilities in the considered maritime application [19].