Separation-independent wearable 6.78 MHz near-field radiative wireless power transfer using electrically small embroidered textile coils

Wagih, M. , Komolafe, A. and Zaghari, B. (2020) Separation-independent wearable 6.78 MHz near-field radiative wireless power transfer using electrically small embroidered textile coils. Energies, 13(3), 528. (doi: 10.3390/en13030528)

Abstract

Achieving a wireless power transfer (WPT) link insensitive to separation is a key challenge to achieving power autonomy through wireless-powering and wireless energy harvesting over a longer range. While coupled WPT has been widely used for near-field high-efficiency WPT applications, the efficiency of the WPT link is highly sensitive to separation and alignment, making it unsuitable for mobile systems with unknown or loose coupling such as wearables. On the other hand, while ultra-high frequency (UHF) and microwave uncoupled radiative WPT (0.3–3 GHz) enables meters-long separation between the transmitter and the receivers, the end-to-end efficiency of the WPT link is adversely limited by the propagation losses. This work proposes radiative WPT, in the 6.78 MHz license-free band, as a hybrid solution to separation-independent WPT, thus mitigating the losses associated with coil separation. Resonant electrically small antennas were fabricated using embroidered textile coils and tuned using L-matching networks, for wearable WPT. The antenna’s efficiency and near-fields have been evaluated numerically and experimentally. The proposed WPT link achieves a stable forward transmission of S21>−1721>−17 dB and S21>−21>−28 dB, independent of coil separation on the XZ and XY planes respectively, in a 27 m33 volume space. The presented approach demonstrates the highest WPT link efficiency at more than 1-m separation and promises higher end-to-end efficiency compared to UHF WPT.

• Item Type: Articles
• Additional Information: This work was supported by the UK Engineering and Physical Sciences Research Council (EPSRC) under Grant EP/P010164/1.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Wagih, Dr Mahmoud

Creator Roles

Wagih, M.: Conceptualization, Formal analysis, Investigation, Writing – original draft

• Authors: Wagih, M., Komolafe, A., and Zaghari, B.
• College/School: College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering
• Journal Name: Energies
• Publisher: MDPI
• ISSN: 1996-1073
• ISSN (Online): 1996-1073
• Published Online: 21 January 2020
• Copyright Holders: Copyright © 2020 The Authors
• First Published: First published in Energies 13(3):528
• Publisher Policy: Reproduced under a Creative Commons license