In this paper we provide new recommendations for a type of antenna design in applications where a human is present in the vicinity of a wireless power transfer (WPT) system by means of power transfer efficiency (PTE) and specific absorption rate (SAR). The interaction between a homogenous human model and different WPT systems is investigated at 13.56 MHz using spherical mode theory antenna model (SMT-AM) and full-wave numerical analysis. The human model exposure and the performance of the proposed WPT system are analyzed further for some typical scenarios. It is shown that the position in which the human model is closer to the receiver is favorable over the position closer to the transmitter, concerning both PTE and SAR. Also, the consideration of variable receiver load indicates that different levels of SAR coupled by degraded PTE can be expected. The proposed antennas are designed and proof of concept WPT measurements are carried out.
"Interaction Between Human and Near-Field of Wireless Power Transfer System," Progress In Electromagnetics Research C,
Vol. 67, 1-10, 2016. doi:10.2528/PIERC16062005
3. Karalis, A., J. D. Joannopoulos, and M. Soljacic, "Efficient wireless non-radiative mid-range energy transfer," Ann. Phys., Vol. 323, 34-48, 2008. doi:10.1109/TAP.2010.2044321
4. Sample, A., D. Meyer, and J. Smith, "Analysis, experimental results, and range adaptation of magnetically coupled resonators for wireless power transfer," IEEE Trans. Ind. Electron, Vol. 58, No. 2, 544-554, Feb. 2010.
5. Yuan, Q., Y. Chen, L. Li, and K. Sawaya, "Numerical analysis on transmission efficiency of evanescent resonant coupling wireless power transfer system," IEEE Trans. Antennas Propag., Vol. 58, No. 5, 1751-1758, May 2010. doi:10.1109/LAWP.2010.2068534
6. Lee, J. and S. Nam, "Fundamental aspects of near-field coupling small antennas for wireless power transfer," IEEE Trans. Antennas Propag., Vol. 58, No. 12, 3442-3449, 2010. doi:10.1109/TAP.2010.2103034
7. Yoon, I. J. and H. Ling, "Realizing efficient wireless power transfer using small folded cylindrical helix dipoles," IEEE Antennas Wireless Propag. Lett., Vol. 9, 846-849, 2010.
8. Tak, Y., J. Park, and S. Nam, "The optimum operating frequency for near-field coupled small antennas," IEEE Trans. Antennas Propag., Vol. 59, No. 3, 1027-1031, Mar. 2011. doi:10.1063/1.1715038
9. Skiljo, M. and Z. Blazevic, "Spherical helices for resonant wireless power transfer," International Journal of Antennas and Propagation, Vol. 2013, 1-12, Article ID 426574, 2013. doi:10.1109/JRPROC.1947.226199
10. Chu, L. J., "Physical limitations of omni-directional antennas," Journal of Applied Physics, Vol. 19, 1163-1175, 1948. doi:10.1109/TAP.1970.1139795
11. Wheeler, H. A., "Fundamental limitations of small antennas," Proc. IRE, Vol. 35, No. 12, 1479-1484, Dec. 1947. doi:10.1109/TAP.2012.2215296
12. Wasylkiwskyj, W. and W. K. Kahn, "Scattering properties and mutual coupling of antennas with prescribed radiation pattern," IEEE Trans. Antennas Propag., Vol. 18, No. 6, 741-752, 1970.
13. Yoon, I. J. and H. Ling, "Investigation of near-field wireless power transfer in the presence of lossy dielectric materials," IEEE Trans. Antennas Propag., Vol. 61, No. 1, 482-488, 2013.
14., IEEE Std C95.1 IEEE Standard for Safety Levels With Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3 kHz to 300GHz, IEEE SCC28, IEEE Standards Department, International Committee on Electromagnetic Safety, The Institute of Electrical and Electronics Engineers, NY, 1999.
15. ICNIRP, "Guidelines for limiting exposure to time-varying electric, magnetic and electromagnetic fields (up to 300GHz)," Health Phys., Vol. 74, 494-522, 1998. doi:10.1109/TEMC.2014.2308013
16. Christ, A., M. G. Douglas, J. M. Roman, E. B. Cooper, A. P. Sample, B. H. Waters, J. R. Smith, and N. Kuster, "Evaluation of wireless resonant power transfer systems with human electromagnetic exposure limits," IEEE Trans. Electromagn. Compat., Vol. 55, No. 2, 265-274, Apr. 2013. doi:10.1109/TPEL.2015.2400455
17. Chen, X. L., A. E. Umenei, D. W. Baarman, N. Chavannes, V. De Santis, J. R. Mosig, and N. Kuster, "Human exposure to close-range resonant wireless power transfer systems as a function of design parameters," IEEE Trans. Electromagn. Compat., Vol. 56, No. 5, 1027-1034, Oct. 2014. doi:10.1109/MAP.2005.1589871
18. Nadakuduti, J., M. Douglas, L. Lu, A. Christ, P. Guckian, and N. Kuster, "Compliance testing methodology for wireless power transfer systems," IEEE Trans. Power Electron., Vol. 30, No. 11, 6264-6273, 2015.
19. Best, S. R., "The performance properties of electrically small resonant multiple-arm folded wire antennas," IEEE Antennas Propag. Mag., Vol. 47, No. 4, 13-27, 2005.
20. Skiljo, M. and Z. Blazevic, "Interaction between humans and wireless power transfer systems," Proc. Soft COM, 15-18, 2014. doi:10.1109/TBME.2006.877798
21. Hasgall, P. A., F. Di Gennaro, C. Baumgartner, E. Neufeld, M. C. Gosselin, D. Payne, A. Klingenb¨ock, and N. Kuster, "IT’IS Database for thermal and electromagnetic parameters of biological tissues,", Version 2.6, www.itis.ethz.ch/database.
22. Hirata, A., O. Fujiwara, and T. Shiozawa, "Correlation between peak spatial-average SAR and temperature increase due to antennas attached to human trunk," IEEE Transactions on Biomedical Engineering, Vol. 53, No. 8, 1658-1664, Aug. 2006.