A Gradual-Width High-Q Self-Resonant Coil Based on Coplanar Waveguide

Self-resonant (SR) coils with high quality factor Q play a critical role for wireless energy transmission systems. In this article, a new single-layered spiral SR coil is introduced based on coplanar waveguide, which consists of two gradual-width spiral copper traces. Compared with traditional equal-width coils, the proposed coil increases the conductive area at specific location. This design significantly reduces loss during the current transmission, further improving Q of the coil. The simulation and experimental tests have confirmed that the proposed coil exhibits an outstanding Q of 436 at a resonant frequency of 13.58 MHz, which is the highest Q of the same frequency and size at present, and indicates a good application prospect for future inductive power transfer (IPT) transmission system.