The increasing sophisticated power and communication demands have motivated a variety of research on simultaneous wireless information and power transfer system, aiming to provide higher power transfer efficiency and improved communication rate. This letter demonstrates that resonant wireless power transfer system with relays can be a candidate to reach these aims. Based on coupled resonator filter theory, mathematical equations for transmission efficiency and bandwidth are derived for arbitrary number of relays. Improved efficiency and bandwidth are verified by equations, simulation and experiments. Experimental results show that under the distance of two times the diameter of the resonator, system efficiency increases from 5.43% (no relay) to 29.47% (one relay) and 38.02% (two relays), with the fractional bandwidth broadened from 1.33% (no relay) to 3.31% (one relay) and 4.47% (two relays) at operation frequency of 42.55 MHz, providing available channel for simultaneous power and data transfer. The procedure for the design of relays is also listed in detail.
2. Wu, J., C. Zhao, J. Du, Z. Lin, Y. Hu, and X. He, "Wireless power and data transfer via a common inductive link using frequency division multiplexing," IEEE Transactions on Industrial Electronics, 2015.
3. Kurs, A., A. Karalis, R. Moffatt, J. D. Joannopoulos, P. Fisher, and M. Soljacic, "Wireless power transfer via strongly coupled magnetic resonances," Sci. Exp., Vol. 317, No. 5834, 83-86, June 2007.
4. RamRakhyani, A. K. and G. Lazzi, "On the design of efficient multi-coil telemetry system for biomedical implants," IEEE Transactions on Biomedical Circuits and Systems, Vol. 7, No. 1, 11-23, February 2013.
5. Zhong, W. X., C. K. Lee, and S. Y. R. Hui, "General analysis on the use of tesla’s resonators in domino forms for wireless power transfer," IEEE Trans. Ind. Electron., Vol. 60, No. 1, 261-270, January 2013.
6. Luo, B., S. Wu, and N. Zhou, "Flexible design method for multi-repeater wireless power transfer system based on coupled resonator bandpass filter model," IEEE Trans. Circuit Syst., Vol. 61, No. 11, 3288-3297, November 2014.
7. Hong, J. S. and M. J. Lancaster, Microstrip Filters for RF/Microwave Applications, Wiley, New York, 2001.
8. Awai, I. and T. Komori, "A simple and versatile design method of resonator-coupled wireless power transfer system," Proc. 2010 ICCCAS, 616-620, July 2010.
9. Sun, E. Y. and S. H. Chao, "Unloaded Q measurement-the critical-points method," IEEE Transactions on Microwave Theory and Techniques, Vol. 4, No. 8, 1983-1986, August 1995.