On the Beneficial Roles of Fading and Transmit Diversity in Wireless Power Transfer with Nonlinear Energy Harvesting

Bruno Clerckx, Junghoon Kim

Research output: Contribution to journalArticlepeer-review

48 Citations (Scopus)


We study the effect of channel fading in wireless power transfer (WPT) and show that fading enhances the RF-to-DC conversion efficiency of nonlinear RF energy harvesters. We then develop a new form of signal design for WPT, denoted as transmit diversity, that relies on multiple dumb antennas at the transmitter to induce fast fluctuations of the wireless channel. Those fluctuations boost the RF-to-DC conversion efficiency thanks to the energy harvester nonlinearity. In contrast with (energy) beamforming, transmit diversity does not rely on channel state information at the transmitter (CSIT) and does not increase the average power at the energy harvester input, even though it still enhances the overall end-to-end power transfer efficiency. Transmit diversity is also combined with recently developed (energy) waveform and modulation to provide further enhancements. The efficacy of the scheme is analyzed using physics-based and curve fitting-based nonlinear models of the energy harvester and demonstrated using circuit simulations, prototyping and experimentation. Measurements with two transmit antennas reveal gains of 50% in harvested DC power over a single transmit antenna setup. The work (again) highlights the crucial role played by the harvester nonlinearity and demonstrates that multiple transmit antennas can be beneficial to WPT even in the absence of CSIT.

Original languageEnglish
Article number8470248
Pages (from-to)7731-7743
Number of pages13
JournalIEEE Transactions on Wireless Communications
Issue number11
Publication statusPublished - 2018 Nov

Bibliographical note

Funding Information:
Manuscript received April 12, 2018; revised July 19, 2018; accepted September 1, 2018. Date of publication September 24, 2018; date of current version November 9, 2018. This work was supported by the EPSRC of U.K. under Grant EP/P003885/1. The associate editor coordinating the review of this paper and approving it for publication was M. Di Renzo. (Corresponding author: Bruno Clerckx.) The authors are with the EEE Department, Imperial College London, London SW7 2AZ, U.K. (e-mail: b.clerckx@imperial.ac.uk; junghoon.kim15@imperial.ac.uk).

Publisher Copyright:
© 2002-2012 IEEE.


  • Fading
  • energy beamforming
  • energy modulation
  • energy waveform
  • nonlinear energy harvesting
  • transmit diversity
  • wireless power transfer

ASJC Scopus subject areas

  • Computer Science Applications
  • Electrical and Electronic Engineering
  • Applied Mathematics


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