Asymmetric Coil Structures for Highly Efficient Wireless Power Transfer Systems

Tae Hyung Kim, Gi Ho Yun, Woong Yong Lee, Jong Gwan Yook

Research output: Contribution to journalArticlepeer-review

60 Citations (Scopus)


A transmitter coil (TX-coil) as well as a receiver coil (RX-coil) has been designed at 6.78 MHz for magnetic resonant wireless power transfer systems not only to have high efficiency at medium distances, which is comparable to the coil dimensions, but also to provide stable efficiency over the position variation of the RX-coil. For mobile devices, the coils should be compact and have low profile and asymmetric, meaning that TX- and RX-coils have different dimensions. In this paper, TX-coil is designed by adding a small coil in series to achieve high quality factor (Q-factor) as well as relatively uniform magnetic field distribution. On the other hand, the scaling factor is introduced for wire width to design RX-coil with higher Q-factor. As a result, the proposed asymmetric coils reveal improved efficiency and degree of freedom in terms of position variation. This has been verified by measuring the system performance, including a power amplifier, full-wave rectifier, regulator, and load. The proposed TX-coil has size of 200 × 200 × 1 mm3, while the size of the RX-coil is 100 × 100 ×0.4 mm3. The power transfer efficiency is 96% and 39% at the transmission distances of 50 and 300 mm, respectively.

Original languageEnglish
Pages (from-to)3443-3451
Number of pages9
JournalIEEE Transactions on Microwave Theory and Techniques
Issue number7
Publication statusPublished - 2018 Jul

Bibliographical note

Publisher Copyright:
© 1963-2012 IEEE.

All Science Journal Classification (ASJC) codes

  • Radiation
  • Condensed Matter Physics
  • Electrical and Electronic Engineering


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