Complex impedance matching for far-field acoustic wireless power transfer

Abstract

In this study, different load matching techniques are analysed to identify the optimum method to deliver power to the receiver for acoustic wireless power transfer systems. Complex impedance matching of the system’s transducers provides an advantage to drive the transmitter off-resonance for cases where there is a resonance mismatch between the transducers due to make, defect or ambient conditions. By studying the effect of impedance matching for different frequencies near the resonance frequency, similar power levels can be achieved for a wider bandwidth of frequencies using complex impedance matching. Thus, increased power can be delivered to the receiver by controlling the frequency of the transmitter, which can be exploited for beam steering along the propagation axis when standing waves are prominent between the transducers. A summary of the power experimentally extracted for the different loading techniques presented in this paper demonstrates a 4 kHz increase in system bandwidth and 140% more power can be delivered by tuning both transducers with complex impedance matching.