Analysis and design of a series self-resonant coil for wireless power transfer

A planar coil structure that exhibits a series self-resonant behavior is developed for wireless power transfer systems which use magnetic resonant coupling. The proposed structure uses two thin, planar, spiral tracks separated by one layer of dielectric. By connecting to alternate ends of each track, the coil shows a series LC impedance, which is often necessary for voltage source inverters. An analytical model for the inductance, capacitance and resistance is used to develop a geometric design method that minimizes resistance given a set of application constraints. Experimental coils made with an FR4 PCB and an Teflon-ceramic PCB verify the proposed structure and modeling.