Design of a switchable driving coil for Magnetic Resonance Wireless Power Transfer

This paper presents design and analysis of a switchable inductor suited for active impedance matching in magnetic resonance wireless power transfer systems. The switchable inductor is compact and can be used as both driving coil at the transmitter side and load coil at the receiver side. We first present the concept through design, simulation and measurement of a three loops coil. This model of the switchable coil is used to study the internal couplings between the loops. The coil was fabricated on PCB with inductances between 130-324 nH. In addition, we demonstrate a ten-loop switchable coil for driving a high Q-factor resonance with an almost linear increase in their mutual inductances, which is verified by measurement results.