# A CSAR 3D Imaging Method Suitable for Edge Computation
## 4 Data Processing  
### Simulation Data Processing  
This section uses simulation data to analyze the proposed algorithm's performance. Here, the radar transmits FMCW signals with a carrier frequency of 9.6 GHz and a bandwidth of 750 MHz. The flight radius of the SRUAV is 600 m, the flight altitude is 300 m, and the flight speed is 7 m/s. Slow time sampling points for one circle of flight total 179,520 s, while fast time sampling points total 1502. The size of the imaging scene is \(20\times 20\times 10\) m\({}^{3}\), which is divided into 3D imaging grids of \(110\times 110\times 23\) based on the range resolution of the echo. There are five point targets in the simulation scene located in two height planes and distributed in the center and periphery of the scene. The distribution of the simulation point targets is shown in Figure 5, and the coordinates of the five point targets in the scene are provided in Table 1.  
The 2D imaging results of CSAR obtained by IRT with a height of z = 5 m are shown in Figure 6. Compared to the imaging results when using the traditional BP and IBP algorithms, 2D imaging under the proposed method is precise and accurate. The X slices of point A and point B are shown in Figure 7. Point A is located in the center of the scene, and the focus position of point A in the two images is the same. However, the imaging resolution of point A proposed in this paper is lower than that of the traditional BP and IBP algorithms. Point B is far from the center of the scene, and the focus position of point A in the two images is the same. The imaging resolution of point B proposed in this paper is similar to that of the traditional BP and IBP algorithms. When the normalized amplitude is 0.707, the corresponding main lobe width is the resolution of the target. A resolution comparison of the A and B points is shown in Table 2. The current imaging resolution (point A 0.36 m and point B 0.36 m) is slightly lower than that of the traditional BP (point A 0.2 m \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Serial Number** & **X (m)** & **Y (m)** & **Z (m)** \\ \hline
1 & 0 & 0 & 5 \\
2 & 5 & \(-\)5 & 5 \\
3 & \(-\)5 & 5 & 0 \\
4 & \(-\)5 & \(-\)5 & 0 \\
5 & 5 & 5 & 0 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Coordinates of the five point targets. Figure 5: Simulated point target distribution diagram. and point B 0.3 m) and IBP algorithms (point A 0.24 m and point B 0.32 m). Nevertheless, the target's position is consistent with the BP algorithm, enabling it to be used for fast CSAR image processing. The 2D imaging results of CSAR with typical heights obtained by IRT are shown in Figure 8. It can be seen that when the height z = 0 m, three points are well focused, and the other two points are defocused into a circle. When the height z = 5 m, two points are in good focus, and the other three are out of focus and form a circle. When the height z = 2.5 m, there is no point target, and the distances from the set point target (z = 0 m and z = 5 m) are basically the same, defocusing all five point targets into circles. These circles are fully consistent with the actual set point targets in the scene. After the X-direction is layered by position, the Hough transform is used to extract the intersection of the defocused circle that changes with height to form a cone. The extraction result of the intersection of typical X-position slices is shown in Figure 9. When x = \(-\)5 m, the peak point after the Hough transform is extracted as shown in Figure 9a; the endpoint of the extracted line is shown as the red \" \" in Figure 9b; and the intersection point of the detected output line is shown as the cyan \" \" in Figure 9b. Here, the two intersection points are consistent with the two-point target with a height of z = 0 m in the scene. When x = 0 m, the peak point after the Hough transform is extracted, as shown in Figure 9c, and the intersection point of the extracted straight line and the detected output straight line is