Analysis of the Double-Layer Printed Spiral Coil for Wireless Power Transfer

As a critical part of the wireless power transfer system via strongly coupled magnetic resonances, the resonant coils must be cautiously designed for the specific resonant frequency and high quality factor. There are some issues needed to be considered and studied in the coil design, such as the coil structure, parasitic parameter extraction, and optimizing. In this paper, the double-layer printed spiral coil is used, which could fully take advantage of the limited space and make larger parasitic capacitance for lower resonant frequency. Using the simplified partial element equivalent circuit method and finite element method, the circuit model with consideration of parasitic parameters and high-frequency losses is built, and the impedance characteristic of coil is simulated, which coincides well with the measurement result. In addition, several elements affecting the high-frequency loss, including the skin effect, proximity effect, and dielectric loss, are discussed for reaching higher quality factor, which is critical for the power transfer system.