Practical Multi-Port Equivalent Circuit Model for Integrated NFC and Wireless Power Transfer Coupler

In this study, we present an integrated four-port coupler that combines independently designed near-field communication (NFC) and wireless power transfer (WPT) couplers for mobile devices. A practical equivalent circuit (PEC) is introduced in which inductive and capacitive couplings are unified using T-model and Pi-model representations, enabling explicit representation of all self- and mutual coupling elements. From this PEC, the complete 4 × 4 S-parameter matrix is derived by converting partitioned trasmission matrices. Full-wave 3D simulations confirm the analytical results, with discrepancies under 2.4 %, which validates both the accuracy of the model and its suitability for multi-port NFC-WPT design.