ABSTRACT
A great deal of behaviour change occurs in a wireless power transfer system before and after the critical coupling value. The critical coupling value is a function of distance because all the other variables in the equation for the coupling coefficient such as the radii of the coils remain fixed once they are created. The critical coupling value is a transition point between the overcoupled regime and undercoupled regime. The critical coupling value corresponds to the greatest distance at which maximum power transfer efficiency is achieved. The factor that affects wireless power transfer is if there exists a mismatch between the input impedance of the transmitting circuit and the source impedance. To avoid signal reflections, the source input impedance should match the source impedance. A better understanding of the circuit theory model of wireless power transfer systems can be derived if the transmitting and receiving circuits are treated as two port networks with input and output impedances.
