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)peer-review

45 Citations (Scopus)
449 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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