Exploiting Current Path Topology for Magnetic Field Shaping in Misalignment-Robust Double-D Wireless Power Transfer Couplers

Lateral misalignment in wireless power transfer (WPT) systems produces position-dependent mutual inductance and degrades coupling robustness. This paper develops a current path-based magnetic field shaping approach for double-D (DD) couplers by embedding a parameterized Hilbert trajectory within the conventional winding. The resulting double-D with Hilbert current path topology (DDH) coupler treats internal current path organization as an electromagnetic design degree of freedom over a prescribed misalignment region under controlled conductor resource constraints. Semi-analytical calculations show that under equal conductor length, the symmetric DDH decreases the area-averaged |M| by 2.86% but increases the locally refined minimum mutual inductance by 21.55% and reduces the spatial coefficient of variation by 8.19%, demonstrating coupling redistribution rather than uniform amplification. Releasing directional symmetry yields a further 2.85% increase in the calculated refined minimum mutual inductance for the anisotropic design. The model agrees with Ansys Maxwell within 0.34% mean absolute relative error (Pearson correlation above 0.9999). Prototype measurements at 120 kHz reproduce the predicted spatial trends. A model-predicted link efficiency evaluation using measured winding parameters and FEM-computed mutual inductances shows no efficiency penalty at alignment and a 5.7-percentage-point gain at the weakest position under optimal load matching. These results establish internal current path organization as a passive field shaping variable for misalignment-robust coupler design.