An automatic tuning assist circuit is coupled with a transmission antenna. The transmission antenna injects a first correction current into, or otherwise draws the first correction current from, the transmission antenna. In the first state, the first auxiliary coil is coupled with the transmission antenna. In this state, the first correction current IA, which corresponds to a current that flows through the first auxiliary coil, is injected into or drawn from the transmission antenna. In the second state, the first auxiliary coil is decoupled from the transmission antenna. In this state, the current that flows through the first auxiliary coil flows through a current path which is independent of the transmission antenna. The state is switched between the first state and the second state with the same frequency as that of the driving voltage.