Anti-efficiency reduction of coil's displacement by using parasitic coil

Used as the transmitting and receiving elements, coils are the most popular elements for wireless power transfer. The parasitic coil or LC booster coil has been used as the part of the receiving element and reported to be effective to increase the wireless Power transfer efficiency so far. In this paper, the maximum transfer efficiency of the wireless power system by using parasitic coil will be calculated both by circuit theory and by using S-parameters or Z-parameters we proposed before, and further the effect of the distance between transmitting and receiving coils will he investigated quantitatively.