## 4 Simulation
### Real Test  
The proposed algorithm was tested using the K-MD2 FMCW radar. K-MD2 is a 24 GHz FMCW radar. Various range resolution settings are possible, but in order to test in the same state as the simulation, the range resolution was set to 0.4 m. The FMCW radar specification is the same as Table 1, which is a MATLAB simulation environment. Measurements were conducted with the K-MD2 FMCW radar, and the signal processing was performed using MATLAB. To isolate the target signals, background noise from the indoor environment was removed. The I and Q data from the digital signals were separated, and subsequent processing followed the same procedures as those used in the MATLAB simulation. The real tests were conducted in the environment shown in Figure 11a. Figure 11b depicts the K-MD2 FMCW radar used in the experimental measurements. Three targets were set, with inter-target distances of 0.4 m and 0.5 m, resulting in a total of 20 test scenarios. Table 5 presents the measurement results of the proposed algorithm, including padding lengths and their corresponding root mean square errors (RMSE). RMSE is a measure of the average squared error between predicted values and actual values. A lower \begin{table}
\begin{tabular}{c c c c} \hline \multicolumn{2}{c}{**Zero Padding**} & \multicolumn{2}{c}{**Neural Network Padding**} & \multicolumn{2}{c}{**Estimated Signal Padding**} \\ \hline \multicolumn{4}{c}{(a)} \\ \hline Same size & 66.1\% & 88.1\% & 92.6\% \\ \hline Various size & 53.5\% & 51.7\% & 78.8\% \\ \hline \multicolumn{4}{c}{(b)} \\ \hline Same size & 66.1\% & 88.1\% & 95.6\% \\ \hline Various size & 53.5\% & 51.7\% & 80.8\% \\ \hline \end{tabular}
\end{table} 
Table 4: (a) Performance results by algorithm when target size is not equal: 1/4 error of existing range resolution. (b) Performance results by algorithm when target size is not equal: 1/2 error of existing range resolution. RMSE indicates higher accuracy, meaning a smaller difference between the actual target positions and the estimated positions. RMSE is defined as shown in Equation (12):  
\[RMSE=\sqrt{\sum_{i=1}^{n}\frac{\left(\frac{y_{i}-y_{i}}{n}\right)^{2}}{n}} \tag{12}\]  
Figure 11: (**a**) Test environment; (**b**) FMCW radar used for measurement. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{4}{c}{(**a**)} \\ \hline  & Target1 & Target2 & Target3 & RMSE \\ \hline Actual position & 1.6 m & 2.0 m & 2.4 m & \\ \hline Original & 1.6 m & X & 2.4 m & 1.155 \\ \hline Twice & 1.8 m & 2.2 m & 2.6 m & 0.2 \\ \hline Four times & 1.8 m & 2.3 m & 2.6 m & 0.238 \\ \hline Eight times & 1.75 m & X & 2.3 m & 1.159 \\ \hline  & Target1 & Target2 & Target3 & RMSE \\ \hline Actual position & 2.0 m & 2.4 m & 2.8 m & \\ \hline Original & 2.0 m & X & X & 2.129 \\ \hline Twice & 2.0 m & 2.4 m & 2.8 m & 0 \\ \hline Four times & 2.0 m & 2.4 m & 2.7 m & 0.058 \\ \hline Eight times & 1.95 m & 2.45 m & 2.75 m & 0.05 \\ \hline  & Target1 & Target2 & Target3 & RMSE \\ \hline Actual position & 2.0 m & 2.4 m & 2.8 m & \\ \hline Original & 2.0 m & X & 2.8 m & 1.386 \\ \hline Twice & 2.2 m & 2.6 m & 3.0 m & 0.2 \\ \hline Four times & 2.1 m & 2.5 m & 2.9 m & 0.1 \\ \hline Eight times & 2.05 m & 2.35 m & 2.7 m & 0.071 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: (**a**) A 0.4 m distance between targets; (**b**) a 0.5 m distance between targets.