Single-Sided Interspiraled Inductive Impedance Matching for Magnetic Resonance Wireless Power Transfer

This paper presents a single-sided impedance matching technique, i.e., matching from only the transmitter or receiver side, using a switchable interspiraled coil. This technique is suited for active impedance matching in magnetic resonance wireless power transfer. The switchable coil consists of 9 selectable, single-turn coils placed in-between the 9.5 turns of a spiraled resonator coil with an inductance of approximately 8 mu H. The self-inductances of the single-turn coils vary between 33-493 nH. The interspiraled coil was realized on a single-sided PCB, making the system compact in size. Circuit analysis and simulation show that the inductance selectability enables impedance matching over a range of distances in a Wireless Power Transfer (WPT) System at 6.78 MHz operation frequency. Measurement and simulation of the efficiency indicate that the proposed interspiraled coil may significantly improve the Power Transfer Efficiency (PTE) when the distance and the load change.