## 4 Performance Evaluation
### Field Test Results  
In this section, the effectiveness of the proposed fusion technique is verified by field tests using our self-developed DVB-S-based McPR system. Some system parameters of the McPR system are summarized in Table 3. To achieve coherent receiving, a 20 MHz external reference is used and inserted into the low-noise block (LNB) to ensure the coherent operation of the rest of the system. The McPR system employs a distributed receiving architecture and enables the receiving of multi-frequency signals simultaneously and independently. In the processing step, the direct path signal (DPS) in the RC is used for coherent processing. More details about the system can be found in our previous work in [12]. A non-cooperative moving vehicle with a bistatic distance of 36 m and a speed of 60 km/h (equivalent to 16.7 m/s) is chosen as the target of interest, as shown in Figure 14. The geometry of data acquisition is also depicted in Figure 15.  
According to the above system parameters: the number of fused multi-frequencies M = 3, where the carrier frequencies received by the radar are 12.395, 12.515, and 12.675 GHz, the sampling frequency of the receiver fs = 100 MHz, and the signal bandwidth B is 36 MHz. Therefore, the Doppler frequency resolution and range resolution of the system are 5.96 Hz and 4 m, respectively. The non-cooperative vehicle is 4.5 m long and 2.2 m wide, so the  
Figure 13: The detection range analysis of the proposed method. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameter** & **Value** & **Parameter** & **Value** \\ \hline Satellite IO & Apstar-6C & Antenna gain/beam width & 36 dBi/1.5\({}^{\circ}\) \\ Freq. of Ch. 1 & 12.395 GHz & Sample rate & 100 MHz \\ Freq. of Ch. 2 & 12.515 GHz & Bandwidth & 36 MHz \\ Freq. of Ch. 3 & 12.675 GHz & CPI & 0.1678 s \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Some experimental parameters. reflection of the target of interest can be identified as a single point-like target under the radar system parameters. In addition, the traffic flow information allows us to estimate its speed and distance to be 16-18 m/s (equivalent to 56.52 km/h, moving away) and 36 m, respectively. The maximum allowable CPI of the McPR is 1 s. The CPI \(T_{int}\) is selected as 0.1678 s for a single channel. The signals in SC and RC are separately acquired and sequentially processed with DDC, a low-pass filter (LPF) using the raised-cosine roll-off filter, and batch-based CAF processing. Finally, the RDMs of different frequency bands are obtained (see Figure 16). From the results in Figure 16, the peak of the target of interest is visible in the same range bin of 36 m, despite the different carrier frequencies. This result also indicates that RCM is not obvious in this case. However, the target's energy is dispersed in multiple Doppler frequency bins from \(-631\) Hz to \(-647\) Hz, and the Doppler spread exceeds more than three Doppler resolution units of the radar system. The above results confirm the existence of MF-DFM in this case. It is also noted that the target at different frequency bands has a high SNR of 36.50, 39.56, and 37.41 dB. Figure 14: The experimental setup for detecting a non-cooperative vehicle, which can be considered as a single point-like target in DVB-S-based McPR. Figure 15: Acquisition geometry. For better evaluating the detection performance of the proposed algorithm in low-SNR conditions, Gaussian white noise is added to the experimental echo data, similar to the work in [45]. This means that the output SNR of the target after adding noise is approximately 7-12 dB, as shown in Figure 17, where the RDMs of three different frequency channels are shown in Figure 17a-c, respectively. One can observe that the target is not clearly visible at the range of 36 m and is submerged below the noise floor. For comparison, Figure 18a,b show a section of Doppler profile data (R = 36 m) without and with adding noise, respectively.