A Novel Technique for Compact Size Wireless Power Transfer Applications Using Defected Ground Structures

This paper presents a novel technique for high efficiency and compact size wireless power transfer (WPT) systems. These systems are based on coupled defected ground structure (DGS) resonators. Two types of DGSs (H-shape and semi-H-shape) are proposed. The semi-H-shaped DGS realizes larger inductance value, and this results in higher WPT efficiency. Instead of using an inductive-fed resonant coupling, we propose capacitive-fed resonant coupling, which reduces the design complexity and enhances the efficiency further. The DGS resonator of both the systems is loaded by chip capacitors for miniaturization. An equivalent circuit using approximate quasi-static modeling is extracted. An analytical design procedure is developed to calculate the optimum design parameters for the proposed WPT systems. The optimized structures are fabricated and measured. The simulation and measurement results are in good agreement. The proposed semi-H-shaped DGS WPT system has a peak efficiency of 73% at a transmission distance of 25 mm. In turn, the figure of merit becomes the highest among the WPT systems proposed so far.