A Novel Interdigital Self-Resonant Coil for Inductive Power Transfer

Self-resonant (SR) coil has aroused extensive research enthusiasm in wireless power transfer due to its high quality factor and easy integration. However, the parasitic capacitance of SR coil is much smaller than traditionally lumped compensation capacitance, which leads to difficulties in miniaturization. An interdigital SR (ISR) coil, consisting of two fingers-like interpenetrating copper conductors, is proposed in this letter, which effectively increases the capacitance of SR coil and reduces the coil size and improves the coil’s quality factor
${Q}$
. Then the analysis and calculation of self-inductance and parasitic capacitance are established. Finally, the proposed ISR coil is designed, manufactured, and measured. The experiment results indicate that, with the diameter of only 50 mm, the proposed ISR coil can achieve a low resonant frequency at 13.75 MHz and a high
${Q}$
of 157.5.