Multilayer Flat Spiral Resonators for Low Frequency Wireless Power Transfer

This paper presents a procedure to characterize a multilayer and multiturn flat spiral resonator through 2D finite element simulations and numerical calculations. The procedure is general and valid for both rectangular and square shapes. It considers all the parasitic effects occurring at low frequencies (from kHz to a few MHz) in complex structures (i.e., skin effect, crowding current density, proximity effect, stray capacitance and dielectric losses). The validation is carried out for two resonators with different shapes and dimensions and variable number of layers and turns. The characterization is supported by comparisons with electromagnetic software and allows the self-resonant frequency and quality factor to be predicted with good accuracy.