Impedance converter circuit and communication terminal device

An antenna device that transmits and receives a high frequency signal in a frequency band range including a first frequency band and a second frequency band whose frequency band range is higher than the first frequency band, the antenna device comprising:

• an antenna element;
• and
• an impedance converter circuit connected to the antenna element;
• wherein
• the impedance converter circuit includes:
• a transformer including a primary coil and a secondary coil, the primary coil being connected to a power feed port;
• a phase shifter circuit connected between the secondary coil of the transformer and an antenna port;
• and
• a bypass circuit connected between the power feed port and the antenna port;
• wherein
• in the second frequency band, an absolute value of impedance of the transformer viewed from the antenna port via the phase shifter circuit is higher than an absolute value of impedance of the bypass circuit;
• and
• in the first frequency band, the absolute value of the impedance of the transformer viewed from the antenna port via the phase shifter circuit is lower than the absolute value of the impedance of the bypass circuit.

A communication terminal device including an antenna device that transmits and receives a high frequency signal in a frequency band range including a first frequency band and a second frequency band whose frequency band range is higher than the first frequency band and an impedance converter circuit connected between the antenna device and a power feed circuit, wherein

• the impedance converter circuit includes:
• a transformer including a primary coil and a secondary coil, the primary coil being connected to a power feed port;
• a phase shifter circuit connected between the secondary coil of the transformer and an antenna port;
• and
• a bypass circuit connected between the power feed port and the antenna port;
• in the second frequency band, an absolute value of impedance of the transformer viewed from the antenna port via the phase shifter circuit is higher than an absolute value of impedance of the bypass circuit;
• and
• in the first frequency band, the absolute value of the impedance of the transformer viewed from the antenna port via the phase shifter circuit is lower than the absolute value of the impedance of the bypass circuit.