# Feasibility Study of Passive Bistatic Radar Based on Phased Array Radar Signals
## 5 Experimental Results  
In this section, some of the field experimental results are given. Figure 11 shows the experimental scenario geometry. The PAR transmitter and the PBR system are located at different locations, the distance between them is 35 km. There is a civil airport in the north of the PBR system with a distance of 48 km, thus ensuring the presence of aircraft targets in the air, which can be used to verify the target surveillance capability of the PBR system. Based on a priori knowledge of the waveform of PAR signals, it can be concluded that there are 81 carrier frequency points of the transmitted signals, which vary from 558 MHz to 643 MHz. Therefore, a supersonic heterodyne receiver down-converts a high radio frequency (RF) signal from the reference antenna into intermediate frequencies (IF) signal by mixing the RF signal with a 600-MHz signal from a Local Oscillators (LO). Figure 12 shows the imaginary part of the time domain signal and the spectrogram of direct wave IF signal. It can be seen from Figure 12 that there are two groups of signals with different CF and BW and that the PRI and PW of different pulses in the same group are different. For direct wave signal, the CF, BW, and PW of the signal are obtained by the parameter estimation method described in Section 3 and the scattered wave signal received by the surveillance antenna is down-converted to baseband combined with the estimated CF. Figure 13 shows the imaginary part of the time domain signal and the spectrogram of the scattered wave baseband signal. Figure 10: Coherent integration via four method: (**a**) MTD, (**b**) FFT, (**c**) NUFFT among slow time, (**d**) Radon-NUFFT. It can be seen that, although the surveillance antenna is not directed to the PAR transmitter, there are still direct wave signals in the surveillance channel, since the surveillance antenna can receive the sidelobe energy from the PAR emitter. However, it is obvious that the SNR of the direct wave in Figure 13 is much lower than that in Figure 12.  
To verify the performance of matched filtering based on reconstructed reference signal, for the baseband signal in Figure 13, the last direct wave pulse signal is intercepted and the time-domain and frequency-domain signals are shown in Figure 14a, while the time-domain and frequency-domain plots of the reconstructed reference signal based on the parameters of the direct wave signal estimated  
Figure 11: The experimental scenario geometry. Figure 12: Time domain waveform and spectrogram of direct wave IF signal. Figure 13: Time domain waveform and spectrogram of scattered wave baseband signal. in the reference channel are shown in Figure 14b, it can be seen that the SNR of the reconstructed reference signal is much higher. Then, the intercepted direct wave signal and the reconstructed reference signal are used for matched filtering of the whole echo signal, and the results are shown in Figure 15; it can be seen that the target echo has a higher SNR after matched filtering using the reconstructed reference signal. Since the CF and BW of the PAR signal are agile for different groups and a group of signal can last for a few seconds, we set 0.2 s as the CPI for the coherent integration of scattered wave signals. A total of 128 pulses in a CPI of the 4 th beam are matched filtered and realigned according to the peak position of the direct wave signal, and the result is shown in Figure 16.  
Figure 14: Time-domain and frequency-domain plots of the intercepted direct wave signal and reconstructed reference signal. (**a**) Intercepted direct wave signal; (**b**) Reconstructed reference signal  
Figure 15: Results of matched filtering using intercepted direct wave signal and reconstructed reference signal.