Free-Positioning and Omnidirectional Wireless Power Transfer Using Self-Decoupled Planar Transmitter Coils

This article proposes a novel free-positioning and omnidirectional wireless power transfer system using self-decoupled planar transmitter (Tx) coils. The proposed planar Tx coils, consisting of three subcoils, are intrinsically self-decoupled. A precise amplitude modulation technique is studied and developed to obtain a 3-D rotating magnetic field. Then, a two-objective optimization considering both receiving uniformity and efficiency is carried out to find the optimal coil structure and corresponding excitation. The planar loop coil, which can be easily integrated into various miniaturized devices, is used as the receiver (Rx) coil. The experimental results confirm that the multiple Rx coils can be powered over any rotation angle in a wide area with over 80% receiving uniformity at two different heights. A total of 1.05 W can be delivered to the loads with a dc–dc efficiency of 10.46% when there are five Rx coils at a height of 80 mm. At both heights of 80 and 100 mm, all receiving ends can receive more than 35 mW when they are arbitrarily distributed over an example charging area of 400 mm × 400 mm, which is suitable for wireless headstages.