Design of an Orthogonally Stacked DD Coil-Split Capacitive Plate Hybrid Coupler for UAV Wireless Charging

This study proposes a hybrid wireless power transfer (WPT) coupler that integrates a Double-D (DD) coil and a Split Capacitive Plate (SCP) for unmanned aerial vehicle (UAV) near-field charging stations. The proposed structure arranges the DD coil and SCP orthogonally in a stacked configuration, enabling simultaneous utilization of both magnetic and electric field coupling paths. The equivalent circuit is composed of integrated inductive and capacitive coupling branches. The overall network is divided into subcircuits to define transmission matrices, which are then converted into a 2 × 2 S-parameter matrix. To verify the analytical model, the equivalent circuit results were compared with 3D full-wave simulation outcomes, showing a discrepancy of less than 8%, which is acceptable considering circuit simplification and parasitic effects. Furthermore, simulation results under positional and rotational misalignment conditions confirm that the proposed coupler maintains stable power transfer efficiency even beyond a 25% offset range. These results demonstrate that the complementary coupling mechanism, where one dominant coupling mode compensates for the attenuation of the other, operates effectively under misalignment. Consequently, the proposed hybrid coupler provides a promising alternative for enhancing misalignment tolerance in UAV near-field wireless charging systems.