Reliable Multiple Cascaded Resonators WPT System Using Stacked Split-Ring Metamaterial Passive Relays.

A new cascaded structure is proposed to improve the coupled KQ -product ( ${K}$ is the coupling coefficient, and ${Q}$ is the unloaded quality factor) and boost the power transfer efficiency (PTE) of the wireless power transfer (WPT) system. The structure consists of four small resonators cascaded together and fed with a single excitation; each consists of two concentric rectangular rings. This cascaded structure can achieve a high PTE of 89.5% at a transfer distance of 20 mm. Afterward, a passive relay system made of stacked metamaterial (MTM) lenses is utilized to extend power transfer distance and address misalignment issues. The proposed WPT system increases the transfer distance up to 80 mm with a PTE of 50%, i.e., the integration with the MTM achieves a 300% improvement in the transfer distance with a reasonable PTE. Then, an assembly of two stacked MTMs is utilized for further extension of the transfer distance. The two stacked MTMs provide an additional 200% enhancement without affecting PTE. A thorough study of the misalignment was executed, showing that the proposed system is capable of transferring power independently of the position of receiver (Rx) with a reasonable PTE. To the best of authors’ knowledge, the proposed structure is the first structure that employed multiple cascaded resonators integrated with the stacked MTM structure for WPT applications.