EARPHONE CABLE ANTENNA DEVICE AND WIRELESS TERMINAL DEVICE

摘要

PROBLEM TO BE SOLVED: To provide an earphone cable antenna device by which good receiving sensitivity can be obtained as compared to the prior art irrespective of an earphone cable length. SOLUTION: An earphone cable 2 with a length L is connected with a tuner 15 via an impedance matching circuit 13 and a variable impedance matching circuit 14. The variable impedance matching circuit 14 includes a varactor diode 63. Based on the length L of the earphone cable 2, a controller 10 controls a reverse bias voltage applied to varactor diode 63 so that the impedance Zp of the earphone cable 2 which is viewed from an output terminal T4 of the variable impedance matching circuit 14 is matched to an input impedance Zin of the tuner 15. COPYRIGHT: (C)2008,JPO&INPIT