The performance of a conventional Class-E2-based WPT system is sensitive to system parameters such as the coil coupling coefficient and load variation. System efficiency decreases rapidly when the coil coupling coefficient and load deviate from their optimum values. In this paper, an impedance matching method and a design procedure are proposed to maintain high system efficiency over a wider range of coupling coefficient and load variations. The load-pull technique is adopted to identify the high-efficiency load region of a Class-E power amplifier (PA), and a double-L-type impedance matching network (IMN) is proposed to transform the load impedance of a Class-E PA into a high-efficiency working region. Compared to a single L-type IMN, a double-L-type IMN is more flexible and has better tuning performance. A 6.78 MHz Class-E2-based WPT system was built to validate the proposed design method. The experimental results show that the proposed double-L-type IMN can significantly attenuate the decline in Class-E PA efficiency when system parameters dynamically change. With a double-L-type IMN, the WPT system could maintain high efficiency (over 55%) under a wider range of coil coupling coefficient and load variations. The peak system efficiency reached 83.2% with 13.7 W output power. The impedance matching method and design procedure in this paper could provide a practical solution for building a high-efficiency WPT system with strong robustness.

In a simultaneous wireless power and data transfer (SWPDT) system using common coils, achieving high-speed communication in high-power wireless charging systems is challenging due to power transfer interference on communication. Based on high-frequency data carrier-based SWPDT (HFDC-SWPDT) technology, this paper proposes an orthogonal-frequency simultaneous wireless power and data transfer (OF-SWPDT) method to minimize interference where the data carrier frequency is orthogonal to the power carrier frequency and its harmonics. In addition, a guard band is inserted between the spectra of power harmonics and data in order to further separate the power and data spectra. Thus, a high-power, high-speed SWPDT system is achieved. Finally, an 11 kW prototype with 64.125 kbps full-duplex communication is developed to validate the proposed method.