DC voltage boosting technique in radio frequency wireless power transfer systems utilising high PAPR digital modulations

Abstract

This work investigates the performance of an envelope detector under high peak-to-average power ratio (PAPR) waveform excitations. First, the use of multi-stage rectifiers is investigated in wireless power transfer systems, as a method to increase the DC output voltage. It is shown that at low input powers, a large number of stages can reduce the efficiency dramatically. Then, high PAPR waveforms are presented as an alternative method to multi-stage rectifiers that can increase the DC output voltage without decreasing the efficiency at low input powers. Simulations and experimental measurements with different multi-tone waveforms and modulation schemes are shown. The results demonstrate that the PAPR and complementary cumulative distribution functions (CCDF) of a waveform significantly influence the RF-to-DC conversion. Using a 5-tone input waveform with −10 dBm power and a 100 kΩ load, the DC output voltage was increased by 32.3%, while using a 256 QAM modulation the output voltage was increased by 12.6%. The results show similar behaviour to that of multi-stage topologies but without decreased efficiencies at low input powers. These results suggest that the use of high PAPR waveforms can decrease the required number of rectifier stages, and hence increase the rectifier efficiency at extremely low input powers.