A Circuit Model-Based Analysis of Magnetically Coupled Resonant Loops in Wireless Power Transfer Systems

Magnetically coupled resonant loops can berepresented by a lumped element circuit model. Each parameter in the lumpedelement model can be expressed as a function of loop geometry and theseparation between the loops; therefore, the geometry can be systematicallychanged, and the power transfer efficiency of the coupled loops can bepredicted. This paper presents a simulation-based efficiency analysis forwireless power transfer systems utilizing magnetically coupled resonant loops.The behavior of power transfer efficiency is studied for various loop geometryparameters, and the simulation results are presented in detail. These resultsclearly show that there is a trade-off between peak efficiency and criticalcoupling distance, both of which depend on the loop size, frequency ofoperation, and source-load impedances. To verify the accuracy model, twoidentical circular loops are fabricated and measured, and the measurementresults agree well with the model.