Power feeding apparatus, power receiving apparatus, wireless power feeding system and method for wireless transfer of power

A power feeding apparatus, power receiving apparatus, wireless power feeding system, and method for wireless transfer of power are provided. The power feeding apparatus includes an impedance detector, a controller, a power transmitter, a variable matching circuit, and a signal transmitter. The controller is configured to provide first control information and second control information based on an impedance detected by the impedance detector. The power feeding apparatus' variable matching circuit is configured to change a variable diameter of a power feeding coil according to the first control information. The power receiving apparatus includes a power receiver, a signal receiver, and a variable matching circuit. The power receiving apparatus' variable matching circuit is configured to change a variable diameter of a power feeding coil according to the second control information provided by the power feeding apparatus.