Efficient Near-Field Beamforming Using Two-Layer Planar Loop Array for Magnetic Resonance Wireless Power Transfer

This letter presents efficient near-field beamforming using two-layer planar loop array resonator for magnetic resonance wireless power transfer (MR WPT). This two-layer structure provides enhanced power transfer efficiency (PTE) of two important functions by adjusting the lumped capacitance of each loop: beamforming and ability of spatial position freedom and spatial alignment freedom with the receiver. The optimal capacitance of each loop can be found using a genetic algorithm (GA). The three types of two-layer loop arrays such as 1 × 1 and 4 × 4, 2 × 2 and 4 × 4, and 4 × 4 and 4 × 4 are designed at an operating frequency of 6.78 MHz. Overall, these two-layer loop arrays improve the overall simulated PTE compared with that of the 4 × 4 single-layer loop array. Especially, the twolayer loop array of 2 × 2 and 4 × 4 provides the most improved beamforming performance and spatial freedom among them. The measured PTE also increases by about 10% compared with that of the 4 × 4 single-layer loop array.