## 4 Simulation and Experimental Results
### Experimental Results  
The proposed WPDT with an ASK modulation circuit scheme has been implemented using the experimental platform depicted in Figure 10. The MOSFET selected for the prototype is the BSS138 PW from Nexperia, benefiting from its advantageous characteristics, such as a low output capacitance of 7 pF and a small on-resistance of approximately 1.2 \(\Omega\). The \begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameters** & **Description** & **Value** \\  & & **(Simulation/Measured)** \\ \hline \(f_{\text{s}}\) & Carrier frequency & 16 MHz/16 MHz \\ \(V_{\text{d,c}}\) & DC input voltage & 3.3 V/3.3 V \\ \(C_{\text{p}}\) & Parallel capacitor & 65 pF/60 pF \\ \(C_{\text{t}}\) & Series capacitor & 40 pF/43 pF \\ \(L_{\text{t}}\) & Transmitter coil & 3 uH/3 uH \\ \(L_{\tau}\) & Receiver coil & 1 uH/1 uH \\ \(L_{\text{a}}\) & Data modulation inductor & 0.2 uH/0.2 uH \\ \(k\) & Coupling coefficient & 0.17/0.17 \\ \(r_{t}\) & Transmitter coil’s ESR & 0.44 O/0.44 \(\Omega\) \\ \(r_{r}\) & Receiver coil’ ESR & 0.36 \(\Omega\)/0.36 \(\Omega\) \\ \(R_{\text{L}}\) & Load resistance & 540 \(\Omega\)/540 \(\Omega\) \\ \(N_{\text{t}}\) & Transmitter coil’s turn number & 8 \\ \(N_{\text{r}}\) & Receiver coil’s turn number & 5 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Parameters of the proposed circuit. Figure 11: Simulation results of the proposed WPDT circuit. **(a)**\(V_{\text{d}}\), \(V_{\text{g}}\), \(I_{\text{t}}\), and \(I_{\text{d}}\) waveforms when the data signal is at a high level. **(b)**\(V_{\text{d}}\), \(V_{\text{g}}\), \(I_{\text{t}}\), and Id waveforms when the data are at a low level. **(c)** Voltage waveform of the receiver coil when the data rate is 3 Mbps. prototype employs TDK's COG capacitors with a capacitance tolerance of 1%. This capacitor material demonstrates outstanding high-frequency characteristics and minimal parameter errors. High-frequency inductors with a self-resonant frequency surpassing 300 MHz have been selected to alleviate the impact of parasitic capacitance. For measurements, a RIGOL oscilloscope with bandwidths of 800 MHz, along with a passive probe with 500 MHz bandwidth, is employed to capture high-frequency signals within the circuit accurately. To minimize measurement errors, the ground wire of the passive probe is substituted with a grounding spring band, ensuring a robust ground connection and enhancing the reliability of measurement data. Additionally, the distance between the transmitter and receiver coils is designed to be 6 mm, considering factors such as the thickness of the body's skin and fat layers. Detailed and tuned parameters are cataloged in Table 1. Furthermore, the FPGA board is employed in this experimental setup to generate the random data signal and compute the BER. Figure 12 depicts two experimental waveforms of modulation state, showcasing \(V_{\text{d}}\), \(V_{\text{g}}\), and \(I_{\text{d}}\). When the data signal was at a high level, the Class-E PA operates in the optimally tuned state, which satisfies the ZVDS and ZVS features, as demonstrated in Figure 12a. The same waveforms for the sub-optimally tuned state when the data signal was at a low level are illustrated in Figure 12b, which satisfies the ZVS conditions. The voltage waveform (\(V_{\text{out}}\)) of the receiver coil, operating at a data rate of 3 Mbps, is presented in Figure 12c. When the data signal was high, the voltage amplitude measures approximately 10.3 V, resulting in a transmitted load power of 98.2 mW. In this operational mode, the input power is 125.4 mW, with an estimated power dissipation of around  
Figure 12: Experimental results of the proposed WPDT circuit. (a) \(V_{\text{d}}\), \(V_{\text{g}}\), and \(I_{\text{d}}\) waveforms when the data signal is at a high level. (b) \(V_{\text{d}}\), \(V_{\text{g}}\), and \(I_{\text{d}}\) waveforms when the data are at a low level. (c) Voltage waveforms of the receiver coil when the data rate is 3 Mbps. 10 mW from the circuit chips. Consequently, the power transmission efficiency reaches 72.5%.