Design of a resonator-coupled WPT system with multiple loads based on measurement with a VNA instead of an oscilloscope

Resonator-coupled wireless power transfer (WPT) systems are designed for an rf power source with constant current and multiple loads with arbitrary resistance. As long as the system does not include a nonlinear element, the system response can be conveniently measured with a vector network analyzer (VNA) that has 50 ohm input/output impedance. The S parameters thus measured are converted to Z parameters, which are invariant to the external circuits. In the next step, the transferred power and transfer efficiency are calculated for infinite ohm power source using the Z parameters of the circuit obtained above. Using this scheme, the response of a multiple load system is calculated for constant current source. The optimum system condition is also studied indicating the filter design concept is effective.