Quantitative analysis of a wireless power transfer cell with planar spiral structures

An emerging technology of wireless power transfer technique based on electromagnetic resonant coupling, also known as witricity, has been drawing a lot of attention from academia as well as from practitioners since it was reported in 2007 by a group of researchers from the Massachusetts Institute of Technology (MIT). In this paper, a prototype with square planar spiral structure based on witricity is proposed. To compute the resonant frequency, an equivalent circuit model is presented and simulated. The impedance matrix is computed by using a formula method and a 3-D finite-element method (FEM) of eddy-current magnetic field. The results indicate that the numerical method has a better accuracy. In order to reduce the resonant frequency, different conditions are analyzed quantitatively to study the relationship between the parameters and the relation of the prototypes with their resonant frequencies. The findings are found to offer a solid foundation for the optimization of witricity prototypes.