# Adaptive 3D Imaging for Moving Targets Based on a SIMO InISAR Imaging System in 0.2 THz Band
## 5 Experiments  
### Experiment Set-up  
In order to verify the proposed scheme to achieve 3D images of the moving targets. Proof-of-principle experiments are carried out with the 0.2 THz SIMO imaging system in laboratory environment. The experiment scene is shown in Figure 7. The SIMO imaging system is fixed on a bi-axial turntable which works as the servo system to adjust the antenna beams in both azimuth and elevation planes. A sliding rail with a length of 2 m is used to  
\begin{table}
\begin{tabular}{l} \hline Step 4: Estimate the range migration during imaging window based on the virtual sum HRRPs. \\ Then perform combined envelope alignment by compensating the same range migration to the range profiles of Rx1, Rx2, and Rx4. \\ Step 5: Estimate the phase error history along slow-time based on the aligned virtual sum HRRPs. \\ Then perform combined phase correction by compensating the same phase error history to the aligned range profiles of Rx1, Rx2, and Rx4. \\ Step 6: Conduct cross-range compression to get the ISAR images of the virtual sum channel, \\ receiving channel Rx1, Rx2, and Rx4. \\ Step 7: Perform interferometry for the ISAR images of Rx1 and Rx2 to obtain the scatterer \\ coordinates in the horizontal direction according to equations (28) and (30). Meanwhile, perform \\ interferometry for the ISAR images of Rx1 and Rx4 to obtain the scatterer coordinates in the \\ vertical direction according to equations (29) and (31). \\ Step 8: Determine the scatterer coordinates in the range direction to acquire the 3D coordinates. \\ \hline \hline Output: 3D InISAR image. \\ \hline \end{tabular}
\end{table}
Table 2: \(Cont\).  
move the targets, and the rail is driven by an electric motor which is remotely controlled by the computer. The sliding rail is symmetrically placed along the azimuth direction and its vertical distance to the radar is about 4.5 m. The targets are placed on a foam plate which is fixed on the sliding rail with the same height as the SIMO antenna array, and the foam plate is tilted with a pitch angle so that the targets are resolvable in the range direction. As shown in Figure 8, the target used in the experiments is a plane model painted with conductive paint coating, which is regarded as a complex target. The size of the model is about 25 cm in length and 20 cm in width. It has to be noted that, due to a lack of a 3D moving platform, only the horizontal motion is considered in this paper, but the tracking and imaging at the presence of 3D movement can be achieved with the same manner.  
Before tracking, the antenna beam is firstly adjusted to capture the targets. As the targets move, the returned echoes are independently received by the four receiving antennas simultaneously and transferred to the computer for real-time processing. With the aim of obtaining stable tracking, the radar works at the step-tracking mode where a consecutive number of echoes are processed to locate the targets. In each step-tracking period, the servo system will adjust the antenna pointing direction adaptively to track the targets. Meanwhile, the received echoes are recorded in local disk for the purpose of imaging in the post-processing.