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Separation-Independent Wearable 6.78 MHz Near-Field Radiative Wireless Power Transfer using Electrically Small Embroidered Textile Coils

School of Electronics and Computer Science, University of Southampton, Southampton SO17 1BJ, UK
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Energies 2020, 13(3), 528; https://doi.org/10.3390/en13030528
Received: 27 November 2019 / Revised: 5 January 2020 / Accepted: 17 January 2020 / Published: 21 January 2020
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 S 21 > 17 dB and S 21 > 28 dB, independent of coil separation on the XZ and XY planes respectively, in a 27 m 3 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. View Full-Text
Keywords: coils; wireless power transfer; electrically small antennas; e-textiles; internet of things; wireless energy harvesting coils; wireless power transfer; electrically small antennas; e-textiles; internet of things; wireless energy harvesting
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  • Externally hosted supplementary file 1
    Doi: 10.5258/SOTON/D1205
    Description: Supplementary file: dataset from the University of Southampton repository
MDPI and ACS Style

Wagih, M.; Komolafe, A.; Zaghari, B. Separation-Independent Wearable 6.78 MHz Near-Field Radiative Wireless Power Transfer using Electrically Small Embroidered Textile Coils. Energies 2020, 13, 528.

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