Design and implementation of compact WPT system using printed spiral resonators

A planar wireless power transfer (WPT) system with printed square spiral resonators is reported. To facilitate its fabrication, both the spiral resonator and its coupling loop are printed on the top and bottom layer of a single FR4 substrate, such that the spiral resonator is driven by the magnetic field of the coupling loop. The utilised coupling loop along with the appropriate matching circuit will improve the overall efficiency. The proposed WPT system which features a measured efficiency of more than 40% is not only compact but also low cost.