Comparison between inductance topologies for resonant wireless power transmission applications

This paper presents a comparison between three different topologies of electrically small inductances used in resonant wireless power transmission applications: the coil, the spiral and the ring. Firstly, the product of the coupling coefficient and the quality factor is validated as a good figure of merit for the comparison of different topologies. A theoretical analysis then shows that the coupling coefficient for the coil and the spiral is independent of the number of turns while the quality factor of the inductance is proportional to the number of turns. Simulation and experimental results are then presented to validate the theoretical results. They demonstrate that if the Q-factor of the capacitor is small compared to the inductance, there is no reason to use more than one turn for the inductance.