Design and Theoretical Analysis of a Hexagonal-Stacked MISO Electric Resonant Coupling Wireless Power Transfer Coupler

This study presents the design of an optimal Electric Resonant Coupling Wireless Power Transfer (ER-WPT) coupler intended for multiple-input multiple-output (MIMO) systems. The proposed coupler features a hexagonal-stacked structure optimized for electric field coupling and consists of three transmitters and one receiver. Analysis of the electromagnetic characteristics in this 3-to-1 configuration can be extended to larger arrays. Theoretical analysis based on a practical equivalent circuit (PEC) model, which incorporates loss elements from measurement, is validated through comparison with 3D full-wave simulations and experimental results. Across three representative receiver positions, the summed transmission coefficient of the MISO structure reaches up to 0.90, while the PEC model agrees with measurements within a maximum deviation of 0.09, confirming high accuracy. Furthermore, the proposed structure demonstrates stable resonance characteristics near 6.78 MHz with reduced frequency shifts under different receiver positions. The key contributions of this work are the proposal of an efficient hexagonal-stacked MISO ER-WPT coupler and a validated equivalent circuit modeling approach that reflects real-world losses, providing a reliable basis for future multi-transmitter/multi-receiver Wireless Power Transfer systems.