The Impact of PAPR on the Wireless Power Transfer in IoT Applications

This paper is dedicated to the experimental study of the impact of multi-tone signal with a high peak-to-average power ratio (PAPR) on the performance of wireless power transfer (WPT) using a single stage Cockcroft-Walton voltage multiplier with HSMS-285C diodes. The study is done using unlicensed sub-GHz frequencies 863 - 868 MHz in a laboratory under real-life conditions. Two types of design of radio frequency (RF) energy harvesting device (with and without matching network) are used to demonstrate PAPR impact on WPT performance. Eight sub-carriers summed in-phase are used to produce a multi-tone signal with a high PAPR level. For WPT results comparison, a single-tone signal with the same average power is exploited. For the experimental implementation of WPT, pairs of directional (LP0410 Log Periodic PCB) and omnidirectional (VERT900) antennas are used. Moreover, during the experiments the distance between transmitting and receiving antennas is being changed up to 3.2m. The main objective of the experiment is to find conditions when multi-tone signal with a high PAPR provides substantially higher output power compared to single-tone signal. The experimental measurement process includes evaluating the average power at the RF rectifier circuit output for different signals, distances, antennas, and RF-DC converter circuit designs. Furthermore, an additional WPT experiment is performed and the analysis of channel characteristics in the frequency range of interest is done to investigate the reason of the difference between the harvested power using single-tone and multi-tone signals.