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International Journal of Antennas and Propagation
Volume 2017, Article ID 1830687, 6 pages
Research Article

Method for Estimating Optimum Free Resonant Frequencies in Overcoupled WPT System

Automotive IT Platform Research Section, Electronics and Telecommunications Research Institute (ETRI), 1 Techno Sunhwan-ro 10-gil, Yuga-myeon, Dalseong-gun, Daegu, Republic of Korea

Correspondence should be addressed to Jae-Ho Lee;

Received 30 January 2017; Revised 27 March 2017; Accepted 30 March 2017; Published 27 April 2017

Academic Editor: Marta Cavagnaro

Copyright © 2017 Dong-Wook Seo and Jae-Ho Lee. 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.


In our previous work, we proposed the method to maximize the output power even in the overcoupled state of the wireless power transfer (WPT) system by controlling free resonant frequencies and derived closed-form expression for optimum free resonant frequencies of the primary and secondary resonators. In this paper, we propose the mutual coupling approach to derive the optimum free resonant frequencies and show the measured power transfer efficiency (PTE) using the transmission efficiency as well as the system energy efficiency. The results of the proposed approach exactly coincide with those of the previous work, and the fabricated prototype achieves the transmission efficiency of about 80% by tuning the free resonant frequencies to the optimum values in the overcoupled state.