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International Journal of Antennas and Propagation
Volume 2016 (2016), Article ID 9365756, 9 pages
http://dx.doi.org/10.1155/2016/9365756
Research Article

A Wearable Wireless Energy Link for Thin-Film Batteries Charging

Department of Engineering for Innovation, University of Salento, Via Monteroni, 73100 Lecce, Italy

Received 26 November 2015; Accepted 28 February 2016

Academic Editor: Jaume Anguera

Copyright © 2016 Giuseppina Monti et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

A wireless charger for low capacity thin-film batteries is presented. The proposed device consists of a nonradiative wireless resonant energy link and a power management unit. Experimental data referring to a prototype operating in the ISM band centered at 434 MHz are presented and discussed. In more detail, in order to facilitate the integration into wearable accessories (such as handbags or suitcases), the prototype of the wireless energy link was implemented by exploiting a magnetic coupling between two planar resonators fabricated by using a conductive fabric on a layer of leather. From experimental data, it is demonstrated that, at 434 MHz, the RF-to-RF power transfer efficiency of the link is approximately 69.3%. As for the performance of the system as a whole, when an RF power of 7.5 dBm is provided at the input port, a total efficiency of about 29.7% is obtained. Finally, experiments performed for calculating the charging time for a low capacity thin-film battery demonstrated that, for RF input power higher than 6 dBm, the time necessary for recharging the battery is lower than 50 minutes.