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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.

Abstract-A wideband slotted multifunctional reconfigurable antenna is proposed for WLAN/WiMAX/UWB/PCS-DCS/UMTS applications. The proposed antenna consists of monopole and spiral sections and microstrip feeding. A microstrip patch on FR4 substrate provides wideband return loss for each application. Total area of the antenna is 34×45 mm 2 that satisfies all the requirements for different applications in a low profile structure. Reconfigurable design is used in this antenna using RF MEMS switches. The proposed antenna has a nearly omnidirectional radiation patterns (doughnut shape) in different frequency bands. The notch is embedded in the ground plane to improve the impedance matching, and the dimensions of this notch are optimized. Moreover, the variation of group delay is about ±2 ns in UWB application. Also a prototype of the proposed antenna is fabricated, and the results are compared with those obtained from simulations. Measured return losses are in good agreement with simulated ones. The proposed antenna has the advantages of multifunctional operation, low profile, low cost and omnidirectional pattern.