Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Room-scale magnetoquasistatic wireless power transfer using a cavity-based multimode resonator


Magnetoquasistatic wireless power transfer can be used to charge and power electronic devices such as smartphones and small home appliances. However, existing coil-based transmitters, which are composed of wire conductors, have a limited range. Here we show that multimode quasistatic cavity resonance can provide room-scale wireless power transfer. The approach uses multidirectional, widely distributed currents on conductive surfaces that are placed around the target volume. It generates multiple, mutually unique, three-dimensional magnetic field patterns, where each pattern is attributed to different eigenmodes of a single room-scale resonator. Using these modes together, a power delivery efficiency exceeding 37.1% can be achieved throughout a 3 m × 3 m × 2 m test room. With this approach, power exceeding 50 W could potentially be delivered to mobile receivers in accordance with safety guidelines.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: Overview of M-QSCR.
Fig. 2: Constructed room-scale resonator.
Fig. 3: Evaluation of power transfer efficiency.
Fig. 4: Evaluation of safety based on SAR.
Fig. 5: Demonstration of room-scale wireless power transfer in a living environment.

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.


  1. 1.

    Da Xu, L., He, W. & Li, S. Internet of Things in industries: a survey. IEEE Trans. Ind. Informat. 10, 2233–2243 (2014).

    Article  Google Scholar 

  2. 2.

    Weiser, M. The computer for the 21st century. SIGMOBILE Mob. Comput. Commun. Rev. 3, 3–11 (1999).

    Article  Google Scholar 

  3. 3.

    Kamalinejad, P. et al. Wireless energy harvesting for the Internet of Things. IEEE Commun. Mag. 53, 102–108 (2015).

    Article  Google Scholar 

  4. 4.

    Brown, W. C. The history of power transmission by radio waves. IEEE Trans. Microw. Theory Techn. 32, 1230–1242 (1984).

    Article  Google Scholar 

  5. 5.

    Shinohara, N. Power without wires. IEEE Microw. Mag. 12, S64–S73 (2011).

    Article  Google Scholar 

  6. 6.

    Strassner, B. & Chang, K. Microwave power transmission: historical milestones and system components. Proc. IEEE 101, 1379–1396 (2013).

    Article  Google Scholar 

  7. 7.

    Garnica, J., Chinga, R. A. & Lin, J. Wireless power transmission: from far field to near field. Proc. IEEE 101, 1321–1331 (2013).

    Article  Google Scholar 

  8. 8.

    International Commission on Non-Ionizing Radiation Protection. Guidelines for limiting exposure to time-varying electric, magnetic, and electromagnetic fields (up to 300 GHz). Health Phys. 74, 494–522 (1998).

  9. 9.

    Sample, A. P., Meyer, D. A. & Smith, J. R. Analysis, experimental results, and range adaptation of magnetically coupled resonators for wireless power transfer. IEEE Trans. Ind. Electron. 58, 544–554 (2011).

    Article  Google Scholar 

  10. 10.

    Ricketts, D. S., Chabalko, M. J. & Hillenius, A. Experimental demonstration of the equivalence of inductive and strongly coupled magnetic resonance wireless power transfer. Appl. Phys. Lett. 102, 053904 (2013).

    Article  Google Scholar 

  11. 11.

    Assawaworrarit, S., Yu, X. & Fan, S. Robust wireless power transfer using a nonlinear parity–time-symmetric circuit. Nature 546, 387–390 (2017).

    Article  Google Scholar 

  12. 12.

    Assawaworrarit, S. & Fan, S. Robust and efficient wireless power transfer using a switch-mode implementation of a nonlinear parity–time symmetric circuit. Nat. Electron. 3, 273–279 (2020).

    Article  Google Scholar 

  13. 13.

    Kurs, A. et al. Wireless power transfer via strongly coupled magnetic resonances. Science 317, 83–86 (2007).

    MathSciNet  Article  Google Scholar 

  14. 14.

    Zhou, J., Zhang, B., Xiao, W., Qiu, D. & Chen, Y. Nonlinear parity-time-symmetric model for constant efficiency wireless power transfer: application to a drone-in-flight wireless charging platform. IEEE Trans. Ind. Electron. 66, 4097–4107 (2019).

    Article  Google Scholar 

  15. 15.

    Kurs, A., Moffatt, R. & Soljačić, M. Simultaneous mid-range power transfer to multiple devices. Appl. Phys. Lett. 96, 1–4 (2010).

    Article  Google Scholar 

  16. 16.

    Hui, S. Y. R., Zhong, W. & Lee, C. K. A critical review of recent progress in mid-range wireless power transfer. IEEE Trans. Power Electron. 29, 4500–4511 (2014).

    Article  Google Scholar 

  17. 17.

    Uno, Y. et al. Luciola: a millimeter-scale light-emitting particle moving in mid-air based on acoustic levitation and wireless powering. Proc. ACM Interact. Mob. Wearable Ubiquitous Technol. 1, 166 (2018).

    Article  Google Scholar 

  18. 18.

    Sample, A. P., Waters, B. H., Wisdom, S. T. & Smith, J. R. Enabling seamless wireless power delivery in dynamic environments. Proc. IEEE 101, 1343–1358 (2013).

    Article  Google Scholar 

  19. 19.

    Chabalko, M. J., Shahmohammadi, M. & Sample, A. P. Quasistatic cavity resonance for ubiquitous wireless power transfer. PLoS ONE 12, 1–14 (2017).

    Article  Google Scholar 

  20. 20.

    Sasatani, T., Yang, C. J., Chabalko, M. J., Kawahara, Y. & Sample, A. P. Room-wide wireless charging and load-modulation communication via quasistatic cavity resonance. Proc. ACM Interact. Mob. Wearable Ubiquitous Technol. 2, 188 (2018).

    Article  Google Scholar 

  21. 21.

    Chabalko, M. J. & Sample, A. P. Resonant cavity mode enabled wireless power transfer. Appl. Phys. Lett. 105, 243902 (2014).

    Article  Google Scholar 

  22. 22.

    Chabalko, M. J. & Sample, A. P. Three-dimensional charging via multimode resonant cavity enabled wireless power transfer. IEEE Trans. Power Electron. 30, 6163–6173 (2015).

    Article  Google Scholar 

  23. 23.

    Sasatani, T., Chabalko, M. J., Kawahara, Y. & Sample, A. P. Multimode quasistatic cavity resonators for wireless power transfer. IEEE Antennas Wireless Propag. Lett. 16, 2746–2749 (2017).

    Article  Google Scholar 

  24. 24.

    Kajfez, D. & Hwan, E. J. Q-factor measurement with network analyzer. IEEE Trans. Microw. Theory Techn. 32, 660–670 (1984).

    Google Scholar 

  25. 25.

    Haus, H. A. & Huang, W. Coupled-mode theory. Proc. IEEE 79, 1505–1518 (1991).

    Article  Google Scholar 

  26. 26.

    Zargham, M. & Gulak, P. G. Maximum achievable efficiency in near-field coupled power-transfer systems. IEEE Trans. Biomed. Circuits Syst. 6, 228–245 (2012).

    Article  Google Scholar 

  27. 27.

    Christ, A., Douglas, M., Nadakuduti, J. & Kuster, N. Assessing human exposure to electromagnetic fields from wireless power transmission systems. Proc. IEEE 101, 1482–1493 (2013).

    Article  Google Scholar 

  28. 28.

    Sunohara, T., Hirata, A., Laakso, I., De Santis, V. & Onishi, T. Evaluation of nonuniform field exposures with coupling factors. Phys. Med. Biol. 60, 8129–8140 (2015).

    Article  Google Scholar 

  29. 29.

    Chen, X. L. et al. Human exposure to close-range resonant wireless power transfer systems as a function of design parameters. IEEE Trans. Electromagn. Compat. 56, 1027–1034 (2014).

    Article  Google Scholar 

  30. 30.

    Institute of Electrical and Electronics Engineers. IEEE Standards Coordinating Committee 28. IEEE Recommended Practice for Measurements and Computations of Radio Frequency Electromagnetic Fields With Respect to Human Exposure to Such Fields, 100kHz–300GHz (IEEE, 2002).

  31. 31.

    Christ, A. et al. Evaluation of wireless resonant power transfer systems with human electromagnetic exposure limits. IEEE Trans. Electromagn. Compat. 55, 265–274 (2013).

    Google Scholar 

  32. 32.

    Lin, D., Zhang, C. & Hui, S. Y. R. Mathematic analysis of omnidirectional wireless power transfer—Part-II three-dimensional systems. IEEE Trans. Power Electron. 32, 613–624 (2017).

    Article  Google Scholar 

  33. 33.

    Choi, B. H., Lee, E. S., Sohn, Y. H., Jang, G. C. & Rim, C. T. Six degrees of freedom mobile inductive power transfer by crossed dipole Tx and Rx coils. IEEE Trans. Power Electron. 31, 3252–3272 (2016).

    Article  Google Scholar 

Download references


This work was supported by a Grant-in-Aid for JSPS Fellows JP18J22537, JST ERATO grant number JPMJER1501 and JST ACT-X grant number JPMJAX190F. We thank M. J. Chabalko for discussions. We also thank K. Narumi, H. Ogata and T. Ikeuchi for help in the video production.

Author information




T.S., Y.K. and A.P.S. designed the research. T.S. proposed the initial concept, conceived the theory, implemented the system, performed the experiments/analysis and wrote the manuscript. All the authors reviewed and commented on the manuscript. Y.K. and A.P.S. provided the resources. Y.K. supervised the project.

Corresponding author

Correspondence to Takuya Sasatani.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Peer review information Nature Electronics thanks Jenshan Lin and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Figs. 1–11, Table 1 and Notes 1 and 2.

Supplementary Video 1

Overview of the room-scale resonator, including the resonator structure, mounted lumped capacitors, covered range and an animation of the oscillating current/magnetic field.

Supplementary Video 2

Demonstration of room-scale wireless power transfer in a living environment.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Sasatani, T., Sample, A.P. & Kawahara, Y. Room-scale magnetoquasistatic wireless power transfer using a cavity-based multimode resonator. Nat Electron 4, 689–697 (2021).

Download citation


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing