To quantify how planar coil geometry and shielding affect magnetically coupled resonant WPT, a coupling calculation model including magnetic shielding was built and validated using finite-element analysis. A planar-symmetric inner-square–outer-circular coil is proposed. Under equal cross-section and material conditions, it delivers higher mutual inductance and transfer efficiency than conventional windings. To balance coupling, leakage, and weight, an aluminum plate–honeycomb ferrite composite shielding structure was proposed. Comparative experiments confirmed that this composite shielding structure exhibits the strongest anti-misalignment capability. The use of ferrite can enhance mutual inductance by 2.58 times, and the proposed optimized ferrite structure can save 23.3% of ferrite usage on one side without sacrificing system performance. A lab-scale prototype operating at 100 kHz achieves a 100 W peak output with 93.8% efficiency and a surface power density of 0.013 W/mm2. Environmental tests (20–90 °C, 30%–95% RH) show stable output, and the measurements agree with the model, indicating that the proposed planar-symmetric, lightweight coupler is a practical candidate for stratified downhole systems.
Li et al. (Sun,) studied this question.