###### Abstract  
Wireless power and data transmission (WPDT) solutions for medical implants are highly desired. However, achieving a high-power transmission efficiency and data rate simultaneously over an inductive link remains a significant challenge. This paper presents an innovative WPDT circuit that incorporates additional MOSFETs with an inductor in a Class-E power amplifier (PA), achieving amplitude-shift keying (ASK) modulation to address this issue. Firstly, the efficiency of the inductive power transmission link and Class-E PA was analyzed, providing design insights. Then, leveraging the insights, the proposed circuit was designed in such a way that it could effectively switch between two load networks to maintain high transfer efficiency for ASK modulation. Based on the load networks, the relationship between introducing the inductor's value and the data modulation index (MI) was derived to help achieve the desired high-power transmission efficiency. Additionally, the design and calculation of the proposed circuit are also presented. Finally, the proposed circuit was validated through simulations and experiments, demonstrating a power delivery to a load of 84.1 mW with a power transmission efficiency of 70.8% at a data rate and carrier frequency of 3 Mbps and 16 MHz, respectively. Furthermore, the bit error rate (BER) is less than \(10^{-6}\) with an MI of 10%. wireless power and data transmission (WPDT); medical implants; amplitude-shift keying (ASK); Class-E power amplifier +
Footnote †: journal: Accepted: 2 February 2024  
The Class-E PA's two critical parameters determine the transmitter coil's voltage amplitude: the quality factor (\(Q\)) and the input DC voltage. These parameters can be adjusted to achieve data transmission, such as on-off keying (OOK) and amplitude-shift keying (ASK) modulation schemes. Moreover, by changing the Class-E PA's carrier frequency and phase, the frequency-shift keying (FSK) and phase-shift keying (PSK) modulations can be implemented for data transmission. Various methods have been reported to enhance power transmission efficiency and data rates. Typically, two pairs of coils are used--one for power and one for data [16; 17; 18; 19]. This setup can boost power transmission efficiency and data rates but may lead to complex circuitry and increased size. Additionally, mutual inductance coupling between coils can cause power interference and a high bit error rate (BER) [7; 20]. In contrast, using a single coil for wireless power and data transmission (WPDT) can effectively resolve interference, reduce the BER, and maintain a compact size [21; 22; 23]. For the single-coil method, several modulation schemes have been proposed to improve the power transmission efficiency and data rates. Despite efforts to address this challenge using modulation methods like OOK [24], FSK [25], and PSK [26], the challenge still persists. For instance, the high bandwidth required for FSK modulation can increase power loss and circuit complexity. Additionally, the power consumption of demodulator circuits for both FSK and PSK can outweigh their advantage [27]. OOK modulation, despite achieving a 100% modulation index (MI) to minimize the BER, has a lower power transmission efficiency compared to other modulation methods [16]. ASK modulation addresses former modulation schemes' limitations because of its lower power consumption and simpler structure design [20]. Reference [24] introduces an OOK modulation scheme that controls the input voltage to facilitate power and data transmission. However, despite its simplicity, the transmission efficiency of this scheme is limited to 21%. To improve power transmission efficiency, reference [28] presents a switchable tuned network integrated into the Class-E power amplifier (PA) to transmit power and data. This approach involves additional tuned networks and switching devices to achieve ASK modulation.