Angular misalignment is an issue for many potential applications of wireless power transfer (WPT). It is necessary to keep coupling coefficient, especially the magnetic coupling to be insensitive to angular misalignment. This paper analyzes the coupling between the spiral resonators when one resonator rotates with respect to the other. The quantitative data of magnetic and electric coupling components as well as the total coupling coefficient in angular misalignments are presented. Furthermore, a 3D spiral resonator which is less sensitive to angular misalignment is proposed. The coupling when the 3D spiral rotates is studied and the results of analysis and experiment both show that the proposed 3D spiral resonator can keep coupling coefficient at a certain level under angular misalignment.
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