Shielded loops for wireless non-radiative power transfer

In this paper, the design and results of a shielded loop wireless non-radiative power transfer (WNPT) system for mid-range distances is presented. First, the theory behind WNPT is studied from a circuit (quasi-static) perspective. From a quasi-static model, important performance metrics are established. The experimental results of a prototype system of two resonant shielded loops are also reported. Unlike previous work, these loops are directly fed. Additionally, they exhibit a predominantly magnetic response, whereas the helical loops used in the initial demonstration of WNPT had a significant electric dipole moment. Matching conditions for maximum RF-in to RF-out power transfer are considered, and the corresponding matching networks are designed.