Waveforms and End-to-End Efficiency in RF Wireless Power Transfer Using Digital Radio Transmitter

Nachiket Ayir, Taneli Riihonen, Markus Allen, Marcelo Fabian Trujillo Fierro

Research output: Contribution to journalArticleScientificpeer-review


We study radio frequency (RF) wireless power transfer (WPT) using a digital radio transmitter for applications where alternative analog transmit circuits are impractical. An important parameter for assessing the viability of an RF WPT system is its end-to-end efficiency. In this regard, we present a prototype test bed comprising a software-defined radio (SDR) transmitter and an energy-harvesting receiver with a low resistive load; employing an SDR makes our research meaningful for simultaneous wireless information and power transfer (SWIPT). We analyze the effect of clipping and nonlinear amplification at the SDR on multisine waveforms. Our experiments suggest that when the direct current (dc) input power at the transmitter is constant, high peak-to-average power ratio (PAPR) multisines are unsuitable for RF WPT over a flat-fading channel, due to their low average radiated power. The results indicate that the end-to-end efficiency is positively correlated with the average RF power of the waveform and that it reduces with increasing PAPR. Consequently, digital modulations, such as phase shift keying (PSK) and quadrature amplitude modulation (QAM), yield better end-to-end efficiency than multisines. Moreover, the end-to-end efficiency of PSK and QAM signals is invariant to the transmission bit rate. An in-depth analysis of the end-to-end efficiency of WPT reveals that the transmitter efficiency is lower than the receiver efficiency. Furthermore, we study the impact of a reflecting surface on the end-to-end efficiency of WPT and assess the transmission quality of the information signals by evaluating their error vector magnitude (EVM) for SWIPT. Overall, the experimental observations of end-to-end efficiency and EVM suggest that, while employing an SDR transmitter with fixed dc input power, a baseband quadrature PSK signal is most suitable for SWIPT at large, among PSK and QAM signals.

Original languageEnglish
Pages (from-to)1917-1931
Number of pages15
JournalIEEE Transactions on Microwave Theory and Techniques
Issue number3
Publication statusPublished - 2021
Publication typeA1 Journal article-refereed


  • Nonlinear distortion
  • radio frequency (RF) energy harvesting (EH)
  • simultaneous wireless information and power transfer (SWIPT)
  • software-defined radio (SDR)
  • wireless power transfer (WPT).

Publication forum classification

  • Publication forum level 2

ASJC Scopus subject areas

  • Radiation
  • Condensed Matter Physics
  • Electrical and Electronic Engineering


Dive into the research topics of 'Waveforms and End-to-End Efficiency in RF Wireless Power Transfer Using Digital Radio Transmitter'. Together they form a unique fingerprint.

Cite this