ANTENNA DEVICE AND COMMUNICATION TERMINAL DEVICE

摘要

This antenna device (101) is provided with an antenna element (11) and an impedance transformation circuit (35) which is connected to the antenna element (11). The impedance transformation circuit (35) is inserted between the antenna element (11) and a feed circuit (30). The impedance transformation circuit (35) is provided with a first series circuit (26) in which a first coil-shaped conductor (L1a) and a second coil-shaped conductor (L1b) are serially connected, and a second series circuit (27) in which a third coil-shaped conductor (L2a) and a fourth coil-shaped conductor (L2b) are serially connected. The first coil-shaped conductor (L1a) and the second coil-shaped conductor (L1b) configure a closed magnetic circuit through which a closed loop of a first magnetic flux passes, and the third coil-shaped conductor (L2a) and the fourth coil-shaped conductor (L2b) configure a closed magnetic circuit through which a closed loop of a second magnetic flux passes. As a result, the antenna device performs impedance-matching with the feed circuit over a wide frequency band.