# Near-Field-Based 5G Sub-6 GHz Array Antenna Diagnosis Using Transfer Learning
## 3 Experiments with Simulation-Based Data
### Classification of the Failure of Specific Port of Array Antenna  
Specific failure port diagnosis of the array antenna was conducted in the same environment as that for its normal/abnormal diagnosis. The excitation signal of a specific port was assumed to be normal when the amplitude exceeded 0.9 and the phase ranged from \(-10^{\circ}\) to \(10^{\circ}\), and when all ports satisfied the normal condition, the case was assumed to be passed. When many ports were assumed to fail, the number of cases became extremely large. Thus, data were extracted by assuming failure for only one port; the network has 17 classification classes. The details are provided in Table 4. Examples of the near-field distribution for a specific port failure are shown in Figure 4. A total of 19,000 samples were obtained by extracting 3000 sample data for the pass case and 1000 samples for each 16 failure port cases.  
The total training time was 2 h 15 min 57 s, and the accuracy of the specific failure port diagnosis network for 3800 test data was 95.24% (3619/3800). While reducing the pass and failure data for each port at the same rate, the minimum number of sample data that can diagnose a specific failure device was obtained. To this end, the training option was maintained, and the accuracy of the trained network by the number of sample data was compared (see Table 5). The accuracy reached approximately 95% or more, and the minimum number of sample data that achieved 95% accuracy was 10,000.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **Port 1** & **Port 2** & **Port 3** & **Port 4** &... & **Port 16** \\ \hline
**Pass** & Normal & Normal & Normal & Normal &... & Normal \\ \hline
**Port 1 Failure** & Abnormal & Normal & Normal & Normal &... & Normal \\ \hline
**Port 2 Failure** & Normal & Abnormal & Normal & Normal &... & Normal \\ \hline
**...** &... &... &... &... &... &... \\ \hline
**Port 16 Failure** & Normal & Normal & Normal & Normal &... & Abnormal \\ \hline \hline \end{tabular}
\end{table}
Table 4: Specific port failure classification criteria for array antennas.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{5}{c}{**Number of Sample Data**} \\ \cline{2-5}  & **500** & **1000** & **3000** & **5000** & **10,000** \\ \hline
**Accuracy** & 86.0\% & 99.0\% & 99.5\% & 99.2\% & 99.6\% \\ \hline
**Execution time** & 0 h 03 m 09 s & 0 h 07 m 10 s & 0 h 21 m 15 s & 0 h 35 m 22 s & 1 h 07 m 46 s \\ \hline \hline \end{tabular}
\end{table}
Table 3: Normal/abnormal diagnosis result of array antenna by number of sample data.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{5}{c}{**Number of Sample Data**} \\ \cline{2-5}  & **3000** & **5000** & **10,000** & **15,000** & **19,000** \\ \hline
**Accuracy** & 91.04\% & 92.11\% & 95.00\% & 94.60\% & 95.24\% \\ \hline
**Execution time** & 0 h 18 m 47 s & 0 h 31 m 55 s & 1 h 04 m 46 s & 1 h 37 m 07 s & 2 h 15 m 57 s \\ \hline \hline \end{tabular}
\end{table}
Table 5: Specific port failure diagnosis results for array antenna by number of sample data.