## 4 Results  
The performance of the proposed range ambiguity suppression method has been analyzed by processing full-polarization SAR data from Gaofen-3 sensor strip mode which acquired in the near Argun River of Inner Mongolia (the parameters are listed Table 1). Figure 4 shows the HH polarization and VV polarization SAR images acquired by applying standard Chirp-Scaling algorithm to the echo data with no ambiguity suppression process. There are some obvious bright lines along range direction in the top left of the two images which have serious implications on the visual effect and subsequent applications. Considering the technology of alternatively up and down chirp modulation implemented by Gaofen-3 satellite, the bright lines in the image could be the defocusing range ambiguous signals which hold strong intensity. Figure 4: GF-3 satellite images in full-polarization strip mode which acquired in the near Argun River of Inner Mongolia. (**a**) is the HH-polarization mode, (**b**) is the VV-polarization mode. Figure 5 shows the image of ambiguous area targets by processing the HH polarization echo data, where (**a**) represents the azimuth matched filter \(R_{ref}\) with \(n=-1\) when (**b**) represents the \(n=+1\). To find the right \(n\) of the main ambiguous area, entropy values of the two are calculated according to Equation (17). The results are as follows:  
\[ \begin{array}{l}E_{n=1}=2.8438\\ E_{n=-1}=0.1278\end{array}  \tag{25}\]  
It's obvious that the focusing performance of the result with n = \(-1\) is better than that with n = +1, with which we can suppose that the main ambiguous area of the bright lines is with \(n=-1\). The center latitude and longitude information can be calculated according to the Equations (18)-(20) and Table 1.  
\[ \begin{array}{l}Lon=120.921^{\circ}E\\ Lat=48.833^{\circ}N\end{array}  \tag{26}\]  
Figure 6b shows the optical image of the main ambiguous area with the result above. It is the city of Hulun-Buir near the Argun River, which displays a stronger backscatter intensity than the imaging area (Argun River) indeed. Figure 6a shows the corresponding SAR image which is the detail magnification of the top left part in Figure 5a (marked with a red rectangle). The two show a high degree of consistency, which can verify the validity of the ambiguous area imaging process. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Radar Parameter** & **Value** & **Radar Parameter** & **Value** \\ \hline \(\lambda\) & 0.055517 m & PRF & 1292.0768 \\ Transmit Band & 40 MHz & Look angle & 38.91\({}^{\circ}\) \\ Sample rate & 6.667 MHz & Incidence angle & 44.64\({}^{\circ}\) \\ Modulation rate & 1.6006 \(\times\) 10\({}^{12}\) & Near range & 1001.7 km \\ Satellite velocity & (\(-\)1677.18, 5525.42, \(-\)4885.91) & Reference range & 1015.3 km \\ Satellite position & (\(-\)2.870,758.09, 3.815,169.12, 5,287,687.27) & Center range & 1015.3 km \\ Target position & 118.4872\({}^{\circ}\) E, 49.2979\({}^{\circ}\) N & Target radius & 6,368,250 m \\ Equatorial radius & 6,378,140 m & Polar radius & 6,356,755 m \\ equivalent velocity & 7097.4 m/s & Fdc & 6.508994 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: GF-3 Satellite parameters. Figure 5: Image results of the ambiguous area: (**a**) represents the azimuth matched filter \(R_{ref}\) with \(n=-1\); (**b**) represents the azimuth matched filter \(R_{ref}\) with \(n=1\). The parameters of CFAR used in target detection process are shown in Table 2. We set up the target window as 2, the protection window as 8 and the background window as 32, and we finally choose \(t_{1}\) = 2.5-3.5 for the calculation of threshold, which is decided after many times of experiments. In fact, it can reach almost the same detection rate with few error targets for \(t_{1}\) in this interval. Figure 7 shows the detecting results of ambiguous area targets where left parts present ambiguous area imaging results which are typical parts of Figure 6a (marked with red rectangles with serial numbers), right parts the detecting results with \(t_{1}\) = 3.