A Wireless Charging and NFC Integration Technique Based on High-frequency Impedance Characterization of Wireless Charging Coils

The article first investigated and characterized the high-frequency impedance of the wireless charging (WLC) coils. Formulas were then derived to quantify the high-frequency impedance characteristics of the WLC coils deployed in cellphones. Based on the analysis and derived formulas, a WLC and near-field communication (NFC) antenna integration technique was proposed, which utilizes the second inductive region of the WLC coil for NFC antenna operation. Both the WLC load effect and NFC IC load effect was considered, analyzed, and experimentally validated. Furthermore, two techniques to expand the bandwidth of the second inductive region were developed and verified by either simulations or experiments. All the derived formulas and analysis in the article were supported by simulations and experiments.