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A design technique for optimizing resonant coils and the energy transfer of inductive links.

Heidarian, Maryam; Burgess, Samuel J.


Samuel J. Burgess


Power transfer efficiency (PTE) is a key performance parameter in development work on resonant inductive power transfer (IPT) systems. Geometrically optimizing the transmitter (Tx) and receiver (Rx) coil pair is a way of improving the IPT system's efficiency. In this article, a new figure-of-merit (FoM) is proposed to find an optimum coil geometry which maximizes the PTE. The employed FoM parameter, called the 'strong coupling factor' (Pscf), is defined such that its value indicates how strongly the Tx and Rx coils are linked together. Considering the IPT application and its physical size constraints, a proper selection method for identifying the numerical value of Pscf is essential for optimal coil geometry design. This article presents an iterative algorithm to assist in the selection of the most favorable Pscf value which provides maximized PTE for the designed optimum coil geometry. Design examples of two nominal IPT systems at frequencies of 415 and 0.1 MHz are used to investigate the design algorithm. Theoretical calculations show the optimum geometry designed for the IPT system operating at 415 MHz, with coupling coefficient (K) of 0.2, can achieve maximum PTE of 85.70%. Measurements presented from a practical Tx/Rx coil pair in the IPT link operating at 0.1 MHz, with K=0.05, show a PTE of 83.10% against a calculated PTE of 84.11% validating the design process.
This article is an expanded version from the IEEE Wireless Power Week, London, U.K., June 17–20, 2019.


HEIDARIAN, M. and BURGESS, S.J. 2021. A design technique for optimizing resonant coils and the energy transfer of inductive links. IEEE transactions on microwave theory and techniques [online], 69(1), pages 399-408. Available from:

Journal Article Type Article
Acceptance Date Sep 19, 2020
Online Publication Date Oct 20, 2020
Publication Date Jan 31, 2021
Deposit Date Oct 23, 2020
Publicly Available Date Oct 23, 2020
Journal IEEE Transactions on Microwave Theory and Techniques
Print ISSN 0018-9480
Electronic ISSN 1557-9670
Publisher IEEE Institute of Electrical and Electronics Engineers
Peer Reviewed Peer Reviewed
Volume 69
Issue 1
Pages 399-408
Keywords Inductive power transfer (IPT); Magnetic resonance; Power transfer efficiency (PTE); Wireless power transfer (WPT)
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