A Transmitter or a Receiver Consisting of Two Strongly Coupled Resonators for Enhanced Resonant Coupling in Wireless Power Transfer

This paper proposes a novel resonator structure for efficiency and transferred power improvements: a transmitter (a receiver) that consists of two strongly coupled resonators. The two strongly coupled resonators are embedded within a transmitter device (a receiver device) and behave as a single resonator with enhanced performances. Unlike the conventional four-coil system, the first and the fourth resonators are also designed to have high loaded-Q and maximum cross couplings. Therefore, the first and the fourth resonators also take part in the coupled resonance with opposite-side resonators. This provides additional energy exchange path. The exact design guidelines are provided for each different resonance topology from analytical derivation. It is analyzed and experimentally demonstrated that the efficiency and the transferred power are increased by the proposed two-resonator technique. For a 30 cm × 25 cm parallel-resonant transmitter and an 18 cm × 16 cm parallel-resonant receiver at 13-cm distance, the efficiency and the transferred power with the proposed technique are 65.2% and 17.2 W, respectively, whereas those values without the proposed technique are only 37.3% and 6.2 W.