## 4 Fabrication and Measurement
### Magnetic Shielding Performance Verification  
To verify the magnetic shielding performance of the proposed AMCs, magnetic field leakage measurements were performed. The measurement setup is shown in Figure 10a. The Tx coil was fed with +20 dBm input power from an Anritsu MG3692C signal generator at a frequency of 6.98 MHz. A Keysight RF R 50-1 near-field probe was connected to an Anritsu MS2830A signal analyzer for the near-field scanning. The near-field probe has a better resolution of up to 10 cm. Therefore, the magnetic leakage measurement was performed along the \(\pm\)-axis, as shown in Figure 10b, for distances up to 10 cm. The two cases of shielding structure, the IML- and ferrite-only-based AMCs, are shown in Figure 10c,d, respectively. As shown in Figure 11a, the Tx-Rx coil pair in free space shows a uniform magnetic field distribution in both the target and non-target regions. The WPTS with IML-based AMC in Figure 11b clearly shows a high decrease in magnetic field, as in the simulations. In the ferrite-only case presented in Figure 11c, the magnetic field leakage was less than the case without a magnetic shielding structure but was not completely reduced, just as expected from the simulations. Overall, the measured field distribution was in good agreement with that of the simulation. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{\(d\)} & \multicolumn{4}{c}{**Simulated Maximum PTE at 6.78 MHz**} & \multicolumn{4}{c}{**Measured Maximum PTE at 6.98 MHz**} \\ \cline{2-7}  & \multicolumn{2}{c}{**without AMC**} & \multicolumn{2}{c}{**with AMC**} & \multicolumn{2}{c}{**without AMC**} & \multicolumn{2}{c}{**with AMC**} \\ \cline{2-7}  & \multicolumn{1}{c}{**Tx-Rx Only**} & \multicolumn{1}{c}{**Ferrite Only**} & \multicolumn{1}{c}{**SML**} & \multicolumn{1}{c}{**IML**} & \multicolumn{1}{c}{**Tx-Rx Only**} & \multicolumn{1}{c}{**Ferrite Only**} & \multicolumn{1}{c}{**IML**} \\ \hline
10 & 64 & 20.25 & 56.25 & 68.89 & 56.4 & 20.7 & 64.45 \\ \hline
15 & 17.64 & 2.89 & 18.49 & 24.01 & 24.23 & 3.42 & 24.1 \\ \hline
20 & 4.84 & 1 & 4.84 & 6.76 & 8.1 & 0.87 & 7.48 \\ \hline
30 & 0.49 & 0.09 & 0.64 & 1.69 & 2.04 & 0.14 & 1.95 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: PTE performance comparison of the proposed AMC design with the WPTS. Figure 9: Measurement results of the PTE. (**a**) Measurement setup. (**b**) Tx with ferrite only. (**c**) Tx with the IML-based AMC. Lastly, Table 2 shows the performance comparison between the proposed design and the previous work on AMC shielding for WPTS. The proposed IML-based AMC can improve the PTE by approximately 8% at 10 cm with an electrically small volume. It is also electrically thinner than other works reported in the literature. The dielectric-only substrate-based AMC operating at 26.5 MHz has a low profile but slightly larger electrical volume than its operating frequency. It caused a minimal improvement in PTE, approximately 3% at 6 cm and 16% at 1 cm, respectively [26]. Compared with the ferrite-based AMC work in [27], our proposed design offers better efficiency and lighter weight owing to the thinner ferrite profile used at approximately the same AMC surface area. It also shows a lower profile, including the gap between the Tx coil and the AMC. The results based on the ideal PMC in the WPTS suggest a magnetic field improvement of approximately 50% [25]. However, the ferrite and resistive losses from the capacitors affected the PTE. Nevertheless, the proposed AMC still achieved complete magnetic shielding and showed improved PTE at certain distances. This research highlights the suitability of using AMC at a 6.78 MHz WPTS without compromising the PTE performance. In the future, the development of high-permeability materials for high-frequency applications could further improve the PTE and enable the design of a more compact AMC. Figure 11: Measurement results of the magnetic field in dB scale. (**a**) Tx–Rx only. (**b**) Tx with the IML-based AMC. (**c**) Ferrite only. Figure 10: Measurement of magnetic shielding.