Calculation and analysis of near-field magnetic spiral metamaterials for MCR-WPT application

Mu-negative and mu-near-zero metamaterials have great potential for magnetically coupling resonant wireless power transfer (MCR-WPT) application. It is well known that square and circular spiral structures are often applied in MCR-WPT system. However, there is rarely comparative analysis in detail. Here we present the electrical Lorentzian-like model of square and circular spiral resonators to accurately predict the − 1 and 0 points of effective permeability. Combined with semi-empirical equations, analytical process is completely given out. Particularly, all losses of unit cell are calculated in detail. Higher losses are observed in self-resonance circular spiral resonator, resulting in lower quality factor ( Q ). Measurement and full-wave simulation verify the calculated accuracy of effective permeability. To further analyze two spiral metamaterials, their magnetic fields ( H z ) are calculated. By the comprehensive comparison of lumped capacitor and self-resonance metamaterials, the near-field metamaterial with lumped capacitor possesses the better performance. This model can accelerate the design process of near-field metamaterials. These results have the guidance meaning in MCR-WPT application.