## 4 Result of the Experiment and Discussion
### Real Data Processing
The ambiguity in Figure 12 is severe, and the ambiguous component is clearly visible both above \(f_{\rm{prf}}/f_{\rm{dr}}\) and below \(-f_{\rm{prf}}/f_{\rm{dr}}\) of the real target, which substantially affects image interpretation. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Platform velocity & About 100 m/s \\ Platform height & About 6000 m \\ Frequency band & X \\ Signal bandwidth & 200 MHz \\ Azimuth resolution & About 0.5 m \\ Pulse repetition frequency of the original data & 1250 Hz \\ Pulse repetition frequency of the extraction data of & 125 Hz \\ a single channel & 125 Hz \\  & \(x\) & 3.70 m \\ Channel spacing & \(y\) & 0.20 m \\  & \(z\) & 0.08 m \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Airborne dual-channel SAR experiment system parameters. Figure 10: Two-channel data extraction diagram. The distributed SAR HRWS imaging results are shown in Figure 13, where the yellow boxes mark the positions of Target A and B and the red boxes are the positions of their ambiguous components. Figure 13a shows the imaging results by using the traditional TDCM, and Figure 13b shows the imaging results using the proposed method. The traditional TDCM does not consider the motion error of the platform, while the proposed method does consider the error. Furthermore, though the OSM is another traditional method, the number of channels needs to be greater than the number of ambiguous components. Thus, the OSM does not fit this system. Figure 13c-f shows the local zoomed images of Target A and B. Figure 13a,c,e show that, after compensation using the traditional method, although the ambiguity is improved compared to the undersampling case, there is still a large residual. The azimuth ambiguity causes the noise floor of the imaging to increase, and the ambiguous component of the strongly scattered target is still more obvious. After adopting the two-step signal error estimation and compensation method proposed in this paper, considering the range variance of envelope migration and the coupling of motion error and channel error, the image quality is significantly improved after estimating and compensating for the signal error. The motion error is also not considered in the OSM. Therefore, the signal error is not correctly estimated and the ambiguity still exists, as in the traditional TDCM. To further illustrate the effectiveness of the proposed method, Figure 14 shows the azimuth cuts of Target A and B in the scene. Figure 14a,c,e are the azimuth cuts of the imaging results of Target A for the single-channel downsampling, the traditional method, and the proposed method, respectively. Figure 14b,d,f are azimuth sections of the Target B imaging results for the single-channel downsampling, the traditional method, and the proposed method, respectively. The ambiguity suppression capability of the method was measured using the Azimuth Ambiguity-to-Signal Ratio (AASR) [37]. The AASR of Figure 14 is provided in Table 4. Figure 14a,b show that the ambiguous component is severe, and the noise floor is high in the single-channel undersampling case. As shown in Figure 14c,d, after processing by the traditional method, the ambiguity suppression is improved by about 5.6 dB, but ambiguous components are still significant. As shown in Figure 14e,f, the noise floor is reduced by processing with the proposed method, the ambiguity energy is suppressed to below the clutter level, and the imaging quality is significantly improved. Figure 12: Single-channel undersampling imaging results. Figure 13: Distributed SAR HRWS imaging results. (**a**) Imaging results after estimation and compensation of channel error by the traditional method, (**b**) imaging results after estimation and compensation of signal error by the proposed method, (**c**) results of the traditional method for Target A, (**d**) results of the proposed method for Target A, (**e**) results of the traditional method for Target B, and (**f**) results of the proposed method for Target B.