A Flexible 2.45-GHz Power Harvesting Wristband with Net System Output from -24.3 dBm of RF Power

Salah Eddine Adami*, Plamen Proynov, Geoffrey S. Hilton, Guang Yang, Chunhong Zhang, Dibin Zhu, Yi Li, Steve P. Beeby, Ian J. Craddock, Bernard H. Stark

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)

35 Citations (Scopus)
392 Downloads (Pure)

Abstract

This paper presents a flexible 2.45-GHz wireless power harvesting wristband that generates a net dc output from a -24.3-dBm RF input. This is the lowest reported system sensitivity for systems comprising a rectenna and impedance-matching power management. A complete system has been implemented comprising: a fabric antenna, a rectifier on rigid substrate, a contactless electrical connection between rigid and flexible subsystems, and power electronics impedance matching. Various fabric and flexible materials are electrically characterized at 2.45 GHz using the two-line and the T-resonator methods. Selected materials are used to design an all-textile antenna, which demonstrates a radiation efficiency above 62% on a phantom irrespective of location, and a stable radiation pattern. The rectifier, designed on a rigid substrate, shows a best-in-class efficiency of 33.6% at -20 dBm. A reliable, efficient, and wideband contactless connection between the fabric antenna and the rectifier is created using broadside-coupled microstrip lines, with an insertion loss below 1 dB from 1.8 to over 10 GHz. A self-powered boost converter with a quiescent current of 150 nA matches the rectenna output with a matching efficiency above 95%. The maximum end-to-end efficiency is 28.7% at -7 dBm. The wristband harvester demonstrates net positive energy harvesting from -24.3 dBm, a 7.3-dB improvement on the state of the art.

Original languageEnglish
Article number7955016
Pages (from-to)380-395
Number of pages16
JournalIEEE Transactions on Microwave Theory and Techniques
Volume66
Issue number1
Early online date22 Jun 2017
DOIs
Publication statusPublished - 1 Jan 2018

Structured keywords

  • Digital Health

Keywords

  • Boost converter
  • fabric antenna
  • fabric-to-PCB connector
  • Internet of Things
  • power management
  • rectenna array
  • rectenna impedance matching
  • rectennas
  • RF energy harvesting
  • RF power transfer
  • smart fabric
  • T-resonator method
  • textile antenna
  • two-line method
  • Digital Health

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  • Projects

    SPHERE (EPSRC IRC)

    Craddock, I. J., Coyle, D. T., Flach, P. A., Kaleshi, D., Mirmehdi, M., Piechocki, R. J., Stark, B. H., Ascione, R., Ashburn, A. M., Burnett, M. E., Aldamen, D., Gooberman-Hill, R. J. S., Harwin, W. S., Hilton, G., Holderbaum, W., Holley, A. P., Manchester, V. A., Meller, B. J., Stack, E. & Gilchrist, I. D.

    1/10/1330/09/18

    Project: Research, Parent

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