A wireless power transfer system based on quasi‐parity–time symmetry with gain–loss ratio modulation

Wireless power transfer (WPT) systems based on parity–time (PT) symmetry can realize robust power transfer against the fluctuation of distance. There is an exceptional point (EP) that partitions the PT‐symmetric and PT‐broken phase, and it is nonadjustable at the conventional system with unity gain–loss ratio unless changing circuit parameters, which limits the improvement of its transfer performance. This paper proposed a novel quasi‐PT‐WPT system based on gain–loss ratio modulation. The proposed system can operate under different gain–loss condition with constant transfer power and efficiency regardless of coupling coefficient variation at the PT‐symmetric phase, which can enhance either the maximum transfer efficiency or distance alternatively. The proposed system consists of a nonlinear gain with adjustable gain–loss ratio to enable the transfer performance control, which is implemented by the virtual impedance. Experimental results verified the correctness of the theoretic analysis and implied the inherent contradiction between the transfer efficiency and distance.