## 5 Simulation and Experimental Results
### Experiment Results  
In order to verify the effectiveness of TR-RDA in actual received signals with noise, we conducted non-uniform sampling imaging experiments using a 0.3 THz stepped-frequency radar system. The radar system parameters are presented in Table 1, with an azimuth beamwidth of 6.5 degrees and a detectable range of 0-8.333 m. The range and azimuth resolutions can reach 5 mm. The radar operated in stripmap mode, and the raw echo data obtained by the radar exhibited uniformity in the azimuth direction. Suppose there are \(N\) uniformly sampled points in the azimuth direction. To perform non-uniform sampling imaging experiments, we selected \(N_{m}\) (where \(N_{m}<N\)) sampled points with non-uniform spacing from the original uniformly sampled echo data. \begin{table}
\begin{tabular}{c c c c} \hline \hline \(N_{m}\) & **AR-RDA** & **TR-RDA** & **BPA** \\ \hline
150 & 1.0955 & 1.2971 & 1.6504 \\
200 & 1.1043 & 1.3364 & 2.9573 \\
250 & 1.1518 & 1.3379 & 4.7433 \\
500 & 1.1968 & 1.6514 & 16.3716 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The time cost (seconds) of the three algorithms at different \(N_{m}\). Figure 10: Pulse response function of the three algorithms to point target \(B\) when (**a**) \(N_{m}=150\), (**b**) \(N_{m}=200\), (**c**) \(N_{m}=250\). \begin{table}
\begin{tabular}{c c c c c} \hline \hline \(N_{m}\) & **Algorithm** & **PSLR (dB)** & **ISLR (dB)** & **IRW (m)** \\ \hline \multirow{3}{*}{150} & AR-RDA & \(-16.45\) & \(-6.2484\) & 0.0046 \\  & TR-RDA & \(-14.15\) & \(-8.8789\) & 0.0040 \\  & BPA & \(-16.83\) & \(-6.9386\) & 0.0041 \\ \hline \multirow{3}{*}{200} & AR-RDA & \(-10.77\) & \(-7.9966\) & 0.0043 \\  & TR-RDA & \(-13.76\) & \(-9.7141\) & 0.0040 \\  & BPA & \(-14.21\) & \(-7.0163\) & 0.0038 \\ \hline \multirow{3}{*}{250} & AR-RDA & \(-11.29\) & \(-8.5601\) & 0.0043 \\  & TR-RDA & \(-13.87\) & \(-10.6622\) & 0.0040 \\ \cline{1-1}  & BPA & \(-13.16\) & \(-7.5317\) & 0.0039 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Azimuth pulse response characteristics of point target \(B\). A total of three sets of raw data were selected for the experiments. The first and second sets correspond to the echo data obtained by imaging the letter A and an airplane model indoors, respectively, using the radar mounted on a small cart. Figure 11 shows the radar system mounted on the small cart. In the bottom left corner of Figure 11, there is a measuring wheel with a diameter of 14.8 cm. By rotating the measuring wheel a fixed distance, the radar is triggered to emit a signal, ensuring uniform sampling in the azimuth direction. The distance interval for uniform sampling is 0.646 mm. Figures 12a and 13a shows the optical images of the letter A and the airplane model. The minimum slant range from the center of letter A and airplane model to the radar sensor is approximately 1.5 m. The pixel sizes of the first and second sets of raw echo data are \(1927\times 1601\) and \(1100\times 1601\), respectively. The third set echo data was obtained by imaging a pedestrian crosswalk scene outdoors, as shown in Figure 14, using the radar mounted on the top of a car. The radar system has a coverage range of approximately 5 m to 7 m. To maintain uniform sampling in the azimuth direction, a measuring wheel with a diameter of 72 cm was mounted on the car too, providing a sampling interval of 1.8 mm. The pixel size of the raw echo data obtained is \(4313\times 1601\). Figure 11: Experimental setup diagram loaded on a small cart. Figure 12: (a) Letter A optical image; (b) RDA; (c) AR-RDA; (d) TR-RDA; (e) BPA. For these three sets of raw echo data, we selected \(N_{m}\) values of 1156, 551, and 1922, respectively. Figure 15 shows the interval size between the non-uniformly sampled points for these three sets of data. The y-axis represents the interval between adjacent non-uniformly sampled positions, denoted as \(x_{i}-x_{i-1}\) (\(2\leq i\leq N_{m}\)), and the x-axis represents the index \(i\).