Analysis of coupling between magnetic dipoles enhanced by metasurfaces for wireless power transfer efficiency improvement

In this paper, we investigate the possibility of improving efficiency in non-radiative wireless power transfer (WPT) using metasurfaces embedded between two current varying coils and present a complete theoretical analysis of this system. We use a point-dipole approximation to calculate the fields of the coils. Based on this method, we obtain closed-form and analytical expressions which would provide basic insights into the possibility of efficiency improvement with metasurface. In our analysis, we use the equivalent two sided surface impedance model to analyze the metasurface and to show for which equivalent surface impedance the WPT efficiency will be maximized at the design frequency. Then, to validate our theory, we perform a full-wave simulation for analyzing a practical WPT system, including two circular loop antennas at 13.56 MHz. We then design a metasurface composed of single-sided CLSRRs to achieve a magnetic lensing based on the calculated equivalent surface impedance. The analytical results and full-wave simulations indicated non-radiative WPT efficiency improvement due to amplifying the near evanescent field which can be achieved through inserting the proposed metasurface.