ANTENNA MATCHING CIRCUIT, ANTENNA DEVICE, AND COMMUNICATION TERMINAL DEVICE

摘要

This antenna device (101) is provided with: an impedance conversion circuit (2) connected to a power supply circuit (9); an impedance-conversion-ratio adjustment circuit (3); and an antenna (1). The impedance conversion circuit (2) includes a first inductance element (L1) and a second inductance element (L2) which are magnetic field coupled to each other, and forms an autotransformer-type circuit. The impedance-conversion-ratio adjustment circuit (3) includes a third inductance element (L3) connected in series between the impedance conversion circuit (2) and an antenna port (P2), and a capacitance element (C3) shunt connected between the antenna port (P2) and a ground, and corrects the impedance conversion ratio of the impedance conversion circuit (2) in accordance with the frequency band.