Antenna device, and contactless power transfer system

An antenna device configured to be used in a contactless power transmission system, the antenna device comprising:

• a first antenna having a first impedance;
• and
• a second resonant antenna having a second impedance different from the first impedance,
• wherein the antenna device is connected to a power transmission and reception circuit in the contactless power transmission system,
• wherein the first impedance is higher than an impedance of the power transmission and reception circuit, and the second impedance is lower than the impedance of the power transmission and reception circuit,
• wherein the first antenna and the second resonant antenna are connected in parallel,
• the first antenna is an electric field antenna using electric field coupling, and the second resonant antenna is a magnetic field antenna of an LC series resonance circuit using magnetic field coupling,
• the first impedance decreases as the distance to a facing antenna decreases, and
• the second impedance increases as the distance to the facing antenna decreases.