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Analysis and design of capacitively coupled resonators for wireless power transfer system applications Wenngren, Suzanne Elizabeth


An analysis of a capacitive wireless power transfer system is presented to investigate the relationship between spatial impedance variation between the transmitter and receiver. The capacitively coupled link is modeled by an equivalent circuit that includes all coupling paths between the four conductors which make up the link. The final model is formed using an observational tuning approach, beginning with a simple model and iteratively adding complexities introduced by non-idealities until good agreement is shown between experimental and simulated results. Seven resonator configurations are designed to resonate at the ISM band frequencies of 13.56 MHz, 27.12 MHz, and 40.68 MHz, and at critical coupling distances of 10 cm, 20 cm and 30 cm to investigate the impact of each parameter on efficiency and spatial variation. The analysis shows that the behavior of the link over a spatial variation is generally independent of frequency and critical coupling distance, and only the peak efficiency at critical coupling is notably impacted. Measurement results from all seven configurations are shown to verify the analysis. The results indicate that for applications with high power transfer efficiency demands, a lower frequency and smaller critical coupling distances are preferred.

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