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The general coupling matrix representation of bandpass filter (BPF) circuits is a widely used technique that has simplified the analysis and optimization of complex microwave filters. In this paper, we demonstrate a novel application of the general coupling matrix for modeling wireless power-transfer (WPT) systems based on the BPF model of magnetically coupled resonators. Compared to other methods of WPT analysis, our model simplifies accommodation of complex loads and provides direct expressions for impedance matching (IM) in WPT systems. Using this tool, we achieve optimal IM for two resonator systems with a complex load, thus achieving the greatest possible power-transfer efficiency (PTE). Furthermore, our model reveals additional design constraints for optimizing PTE in coupled resonator systems exhibiting low quality factor and small interresonator coupling. Overall, this paper introduces a new, versatile framework for the analysis and optimization of coupled resonator WPT systems. Experimental results are presented, verifying the optimal IM design process. [ABSTRACT FROM PUBLISHER]

In a multiple-receiver wireless power transfer (WPT) system, determining the condition for uniform power distribution at a high transfer efficiency is a challenging issue. In this paper, a selective WPT technique using magnetic resonance coupling (MRC) is introduced for smart power delivery in a multiple-receiver system. The proposed method selectively and exclusively delivers power to only one designated receiver among multiple receivers, eliminating the cross-coupling effect and unbalanced power division problem across the receivers. This is achieved by separating the resonant frequencies of the receivers to isolate the coupling effects between coils. The power division ratio of the receivers is controlled by changing the duration time ratio for power transfer. In this paper, a one-transmitter three-receiver selective MRC system is designed and fabricated. The power distribution is demonstrated under impedance matched condition, showing a power transfer efficiency of 24%–29% at a very small coupling coefficient of 0.01 with a 12-mm-diameter receiver coil. Distance compensation and a one-way communication of time division multiple access are demonstrated for a multiple-receiver system, using the proposed method. [ABSTRACT FROM PUBLISHER]

This letter describes the development and implementation of an impedance-matching (IM) method for achieving optimal power transfer efficiencies (PTE's) in cavity resonator wireless power transfer (WPT) systems. Specifically, we develop a bandpass filter (BPF) circuit model and utilize network analysis to predict and realize maximum achievable PTE to miniature systems enclosed within a hollow metallic cylindrical cavity excited in TM010 resonant mode. Measured PTE results are demonstrated matching closely with the developed theory and circuit simulations. We achieve a peak PTE of 33% to a 5-mm-diameter receive coil that occupies a volume that is 5.23 ×106 times smaller than the volume of the cylindrical cavity. Our achieved PTE is 4 times larger than the PTE achieved to a system with no optimal IM network but only a single resonant capacitor connected in series with the receive coil. The model and results presented illustrate our optimal design methodology for realizing maximum achievable PTE in cavity resonator WPT systems. [ABSTRACT FROM PUBLISHER]