Ning Pan

Amplitude and frequency analysis of multi-sine wireless power transfer

Transmitting multi-sine signals with high peak-to-average power ratio (PAPR) has emerged as an efficient solution to improve the power conversion efficiency (PCE) of wireless power transfer (WPT). This paper analyzes the radio frequency (RF) PCE as a function of the number of tones (Nt) and signal bandwidth (BW) in multi-sine based WPT networks. We show how the energy harvesting efficiency depends on the BW and the non-linear relationship between the instantaneous input amplitude and output voltage. As a result of these, the PCE first increases with increasing Nt and then decreases. We confirm this analysis using measurements. Depending on the circuit chosen for energy harvesting, we can improve PCE of the multi-sine WPT with 25.1% compared to a CW excitation WPT for -5 dBm input power.

Multi-sine wireless power transfer with a realistic channel and rectifier model

This paper analyzes the multi-sine wireless power transfer (WPT) system efficiency under realistic channel conditions. A theoretical system model is established including the wireless channel and the rectifier to derive the output DC power based on the transmitted multi-sine signal. Multi-sine based WPT benefits from the transmission signals high peak-to-average-power-ratio (PAPR). Nevertheless, both simulation and measurement results show that the PAPR of the received signal is decreased when the channel becomes frequency-selective. In a static single-path channel, the rectifiers RF-to-DC power conversion efficiency (PCE) increases first and then saturates with increasing signal bandwidth (BW). This is because the signal PAPR only depends on the number of tones in a frequency-flat channel. The initial improvement is cause by the fact that a small enough envelope period is needed to enable efficient energy harvesting. However, in a static multi-path channel, the rectifier PCE increases first and then decreases with increasing BW of the signal, since the channel becomes more and more frequency-selective with the increasing signal BW. For a 10 MHz two-tone signal, the rectifier PCE difference between a frequency selective or frequency flat channel can be up to 10% for our simulation assumptions.

Measurement-based analysis of the throughput-power level trade-off with modulated multisine signals in a SWIPT system

Simultaneous wireless information and power transfer (SWIPT) has gained interest, especially due to its applicability in the world of Internet of Things. For pure wireless power transfer (WPT), multisine signals have already been shown to increase RF-to-DC power conversion efficiency (PCE) at the receiver which is key in WPT research. In a SWIPT system where the waveforms are modulated for information transfer, however, we expect the modulation scheme to impact both data transmission quality and WPT subsystem efficiency. This paper quantifies by means of an experimental study the impact of QAM and PSK modulated multisine signals, on the power and data transfer efficiency of a SWIPT system, taking into account the often neglected transmitter distortion. Error vector magnitude (EVM) is used as figure of merit for the impact of data transfer efficiency, output voltage ripple for the modulations impact on WPT.