## 3 WPT Model Decomposition Approach Validation and Optimization
The parameters varied by the exhaustive search algorithm are as follows:  
* Tx antenna's reflector, feed line, and dipole lengths (Tx antenna's sub-model parameters);
* Rx antenna's reflector, feed line, and dipole lengths (Rx antenna's sub-model parameters);
* Director length (director's sub-model parameters);
* Separation distance between the Tx and Rx antennas;
* Distance between the Rx antenna's dipole and the director. It was found that for distances between the Tx antenna's dipole and the director, \(d_{\text{dip-dir}}\), larger than 195 mm, a little change in the PTE curve was observed. The distance between the Tx antenna's reflector rear edge and the upper closet side was kept fixed during the optimization process; it was found to have little effect on the high PTE region size. Figure 12a shows the PTE evaluated for the antenna system optimized to achieve the widest high PTE region while ensuring the highest PTE among the models, which provide comparable high PTE region widths. The optimal set of parameter values was obtained by the exhaustive search over a set of parameters for which the simulation data were acquired. It was observed that the presence of the additional conducting strip in the Yagi-like design appreciably extended the high PTE region compared with the dipole antenna, which was also optimized for the maximum region's width. Additionally, it was found that reducing the Rx antenna reflector length can achieve a significantly wider high PTE region, albeit at the expense of a sharp dip occurring close to the right edge of the region, as shown in Figure 12b. In both cases, the PTE was close to 70% over a larger part of the high PTE region. The parameters of the optimized Yagi-like Tx and the Rx dipole antennas are summarized in \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameter** & **Value** & **Parameter** & **Value** \\ \hline Feed line length & 70 mm & Dipole width & 5 mm \\ Feed line width & 5 mm & Substrate width & 180 mm \\ Reflector width & 20 mm & Substrate length & 120 mm \\ Reflector length & 160 mm & Dipole length & 64 mm \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Optimal RX antenna parameter values. Figure 12: The PTE as a function of the separation distance between the Tx and Rx antennas, calculated for the optimal values of the Yagi-like and dipole antenna parameters (see Tables 3 and 4) (**a**) and parameter values giving a more extended high PTE region than the optimal one, but at the cost of a sharp dip almost in the middle of the region and WPT model with a hypothetical mode phase shifter optimized to yield the widest high PTE region (**b**). \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameter** & **Value** & **Parameter** & **Value** \\ \hline Feed line length & 70 mm & Dipole width & 5 mm \\ Feed line width & 5 mm & Substrate width & 180 mm \\ Reflector width & 20 mm & Substrate length & 280 mm \\ Reflector length & 170 mm & Dipole length & 63 mm \\ Director width & 5 mm & Director length & 160 mm \\ Director-to-dipole separation & 180 mm & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Optimal TX antenna parameter values. Tables 3 and 4, respectively. In contrast, those of the sub-optimal model, whose PTE is presented in Figure 12b, are given in Tables 5 and 6. It is worth noting that exactly the sub-optimal model was selected for experimental studies aimed at verifying whether the real-life WPT system implementing the proposed concept can ensure high PTE over relatively large volumes inside the closet to render the received power level less sensitive to the Rx antenna position changes resulting from different suit sizes and imprecise placement. The blue curve shown in Figure 12b is obtained for the WPT system model, where a hypothetical phase shifter is employed in place of the director. The phase shifter's generalized reflection matrix is assumed to be the zero matrix. In contrast, the transmission matrices are identical (under the symmetry assumption), with all the off-diagonal elements set equal to zero, implying no mode conversion.