Magnetically coupled resonant wireless power transfer (WPT) has been employed in many applications, including wireless charging of portable electronic devices, electric vehicles， etc. However, the power transfer efficiency (PTE) decreases sharply due to divergence of magnetic field. Electromagnetic (EM) metamaterial (MM) can control the direction of magnetic fields due to its nega-tive effective permeability. In this paper, MMs with negative effective permeability at radio frequencies (RF) are applied to a WPT system operating at around 16.30 MHz for improvement of PTE. This ul-tra-thin and assembled planar MM structure consists of a single-sided periodic array of the capaci-tively loaded split ring resonators (CLSRRs). Both simulation and experiment are performed to cha-racterize the WPT system with and without MMs. The results indicate that the contribution of high PTE is due to the property of negative effective permeability. By integrating MM in the WPT system, the experimental results verify that the measured PTE with one and two MM slabs have respectively 10% and 17% improvement compared to the case without MM. The measured PTEs of the system at different transmission distances are also investigated. Finally, the proposed MM slabs are applied in a more practical WPT system (with a light bulb load) to reveal its effects. The results verify the efficiency improvement by the realized power received the load.
2. Garnica, J., R. A. Chinga, and J. Lin, "Wireless power transmission: From far field to near field," Proc. IEEE, Vol. 101, No. 6, 1321-1331, 2013.
3. McSpadden, J. O. and J. C. Mankins, "Space solar power programs and microwave wireless power transmission technology," IEEE Micro. Mag., Vol. 3, No. 4, 46-57, 2002.
4. Kurs, A., A. Karalis, R. Moffatt, J. D. Joannopoulos, P. Fisher, and M. Soljacic, "Wireless power transfer via strongly coupled magnetic resonances," Science, Vol. 317, 83-86, 2007.
5. Sample, A. P., D. A. Meyer, and J. R. 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, 2011.
6. Pendry, J. B., "Negative refraction makes a perfect lens," Phys. Rev. Lett., Vol. 85, 3966, 2000.
7. Zhang, X. and Z. Liu, "Superlenses to overcome the diffraction limit," Nat. Mater., Vol. 7, No. 6, 435-441, 2008.
8. Merlin, R., "Radiationless electromagnetic interference: Evanescent-field lenses and perfect focusing," Science, Vol. 317, 5840, 927–929, 2007.
9. Urzhumov, Y. and D. R. Smith, "Metamaterial-enhanced coupling between magnetic dipoles for efficient wireless power transfer," Phys. Rev. B, Vol. 83, No. 20, 205114, 2011.
10. Huang, D., Y. Urzhumov, D. R. Smith, K. H. Teo, and J. Zhang, "Magnetic superlens-enhanced inductive coupling for wireless power transfer," J. Appl. Phys., Vol. 111, No. 6, 064902, 2012.
11. Lipworth, G., J. Ensworth, K. Seetharam, D. Huang, J. S. Lee, P. Schmalenberg, T. Nomura, M. S. Reynolds, D. R. Smith, and Y. Urzhumov, "Magnetic metamaterial superlens for increased range wireless power transfer," Sci. Rep., Vol. 4, 3642, 2014.
12. Zhao, Y. and E. Leelarasmee, "Controlling the resonances of indefinite materials for maximizing efficiency in wireless power transfer," Microw. Opt. Techn. Lett., Vol. 56, No. 4, 867-875, 2014.
13. Huang, Y., H. J. Tang, E. C. Chen, and C. Yao, "Effect on wireless power transmission with different layout of left-handed materials," AIP Adv., Vol. 3, No. 7, 072134, 2013.
14. Che, B. J., G. H. Yang, F. Y. Meng, K. Zhang, J. H. Fu, Q. Wu, and L. Sun, "Omnidirectional non-radiative wireless power transfer with rotating magnetic field and efficiency improvement by metamaterial," Appl. Phys. A, Vol. 116, No. 4, 1579-1586, 2014.
15. Choi, J. and C. H. Seo, "High-efficiency wireless energy transmission using magnetic resonance based on negative refractive index metamaterial," Progress In Electromagnetics Research, Vol. 106, 33-47, 2010.
16. Wang, B., K. H. Teo, T. Nishino, W. Yerazunis, J. Barnwell, and J. Zhang, "Experiments on wireless power transfer with metamaterials," Appl. Phys. Lett., Vol. 98, No. 25, 254101, 2011.
17. Fan, Y., L. Li, S. Yu, C. Zhu, and C. H. Liang, "Experimental study of efficient wireless power transfer system integrating with highly sub-wavelength metamaterials," Progress In Electromagnetics Research, Vol. 141, 769-784, 2013.
18. Wang, B., W. Yerazunis, and K. H. Teo, "Wireless power transfer: Metamaterials and array of coupled resonators," Proc. IEEE, Vol. 101, No. 6, 1359-1368, 2013.
19. Rajagopalan, A., A. K. Ram Rakhyani, D. Schurig, and G. Lazzi, "Improving power transfer efficiency of a short-range telemetry system using compact metamaterials," IEEE Trans. Microw. Theory Techn., Vol. 62, No. 4, 947-955, 2014.
20. Ranaweera, A. L. A. K., T. P. Doung, and J. W. Lee, "Experimental investigation of compact metamaterial for high efficiency midrange wireless power transfer applications," J. Appl. Phys., Vol. 116, No. 4, 043914, 2014.
21. Zhang, Y., H. Tang, C. Yao, Y. Li, and S. Xiao, "Experiments on adjustable magnetic metamaterials applied in megahertz wireless power transmission," AIP Adv., Vol. 5, No. 1, 017142, 2015.
22. Wu, Q., Y. H. Li, N. Gao, F. Yang, Y. Q. Chen, K. Fang, Y. W. Zhang, and H. Chen, "Wireless power transfer based on magnetic metamaterials consisting of assembled ultra-subwavelength metaatoms," EPL-Europhys. Lett., Vol. 109, No. 6, 68005, 2015.
23. Rao, X. S. and C. K. Ong, "Amplification of evanescent waves in a lossy left-handed material slab," Phys. Rev. B, Vol. 68, No. 11, 113103, 2003.
24. Baena, J. D., L. Jelinek, R. Marques, and F. Medina, "Near-perfect tunneling and amplification of evanescent electromagnetic waves in a waveguide filled by a metamaterial: Theory and experiments," Phys. Rev. B, Vol. 72, No. 7, 075116, 2005.
25. Cui, T. J., X. Q. Lin, Q. Cheng, H. F. Ma, and X. M. Yang, "Experiments on evanescent-wave amplification and transmission using metamaterial structures," Phys. Rev. B, Vol. 73, No. 24, 245119, 2006.
26. Cho, Y., H. Kim, C. Song, J. Song, D. H. Kim, H. Kim, and J. Kim, "Ultra-thin printed circuit board metamaterial for high efficiency wireless power transfer," IEEE Wireless Power Transfer Conference (WPTC), 2015.
27. Chabalko, M., B. Jordan, and R. David, "Magnetic field enhancement in wireless power using metamaterials magnetic resonant couplers," IEEE Antennas Wireless Propag. Lett., Vol. 15, 2016.
28. Baena, J. D., R. Marques, F. Medina, and J. Martel, "Artificial magnetic metamaterial design by using spiral resonators," Phys. Rev. B, Vol. 69, No. 1, 014402, 2004.
29. Erentok, A., R. W. Ziolkowski, J. A. Nielsen, R. B. Greegor, C. G. Parazzoli, M. H. Tanielian, S. A. Cummer, B. I. Popa, T. Hand, D. C. Vier, and S. Schultz, "Lumped element-based, highly sub-wavelength, negative index metamaterials at UHF frequencies," J. Appl. Phys., Vol. 104, No. 3, 034901, 2008.
30. Chen, W. C., C. M. Bingham, K. M. Mak, N. W. Caira, and W. J. Padilla, "Extremely subwavelength planar magnetic metamaterials," Phys. Rev. B, Vol. 85, No. 20, 201104, 2012.
31. Smith, D. R., D. C. Vier, Th. Koschny, and C. M. Soukoulis, "Electromagnetic parameter retrieval from inhomogeneous metamaterials," Phys. Rev. E, Vol. 71, No. 3, 036617, 2005.
32. Duong, T. P. and J. W. Lee, "Experimental results of high-efficiency resonant coupling wireless power transfer using a variable coupling method," IEEE Microw. Wireless Compon. Lett., Vol. 21, No. 8, 442-444, 2011.