Co-optimization of efficiency and load modulation data rate in a wireless power transfer system

In-band load modulation as a means of transferring information from a wirelessly-powered client device to a power provider in a wireless power transfer (WPT) system has long been considered to have an unacceptable impact on the efficiency of power transfer. Conventional load modulation involves either completely or severely detuning the receive coil in order to produce a detectable amplitude shift at the power provider side and thereby transfer information. In this work, we analyze the impact of load modulation on system efficiency by considering the power consumption of the transmit power amplifier (PA) and identify a tradeoff between communication capability and end-to-end wireless power transfer efficiency. We also determine how to select a load modulation strategy which reduces the degradation in power transfer efficiency while maintaining high-contrast uplink signaling. Finally, we explore the use of coherent demodulation (IQ demodulation) to reduce the mismatch requirement on a load modulation system by improving the power provider's sensitivity to load modulated signaling.