Combined-harmonics wireless power transfer system

A technique for wireless power transfer (WPT) efficiency improvement by a proper design of the excitation waveform is presented. This improvement is obtained on the one hand by a combined-harmonics excitation, and on the other hand by exploiting multiple-resonance coupled resonators. In contrast to wireless communications, there is no constraint on the linearity of the transmitter and receiver in a WPT system. Therefore, the impact of the excitation waveform on the power transfer efficiency with the help of an analytical model is investigated. An optimum excitation waveform is determined to maximise the power transfer efficiency. Thereafter, the authors concentrate on designing a multiple-resonance coupled resonator system that is consistent with the determined excitation waveform. This work introduces a non-uniform spiral resonator for controlling the self-resonant frequencies, which is consistent with the required excitation waveform. The performance of the designed coupled resonators is then evaluated using a 3D finite-element method and experiments. The numerical simulation and experimental results are in good agreement, verifying the validity of our design.