Maximum gain enhancement in wireless power transfer using anisotropic metamaterials.

We present an analysis for metamaterial (MM) enhanced wireless power transfer (WPT) that includes new results revealing the impact of magnetostatic surface waves and their degradation of WPT efficiency. Our analysis shows that the commonly used fixed loss model used by previous works leads to the incorrect conclusion regarding the highest efficeincy MM configuration. Specifically, we show that the "perfect lens" configuration provides lower WPT efficiency enhancement in comparison to many other MM configurations and operating conditions. To understand why, we introduce a model for quantifying loss in MM-enhanced WPT and introduce a new figure of merit on efficiency enhancement, [Formula: see text]. Using both simulation and experimental prototypes, we show that while the "perfect-lens" MM achieves a field enhancement of four times the other configurations considered, its internal loss due to magnetostatic waves significantly reduces its efficiency-enhancement. Surprisingly, all the MM configurations analyzed other than the "perfect-lens" achieved higher efficiency enhancement in simulation and in experiment than the perfect lens.