Efficient Magnetic Resonance SIMO WPT Insensitive to Load Impedance at Short Distances

In general, it is known that magnetic induction (MI) wireless power transfer (WPT) is used at a short distance (~several millimeters) and magnetic resonance (MR) WPT is applied at a longer distance (more than several tens of centimeters). In this letter, it is shown that the MR coil can be robustly designed to have higher efficiency, even when the load impedance changes significantly at short distances. The simulated power transfer efficiencies of MI and MR coil show that the MR coil was more insensitive to load impedance than the MI coil. A 1:4 single input and multiple output (SIMO) MR coil wasdesigned and fabricated. Its performance with the variation of load impedance was verified through measurement.