| 摘要 |
PROBLEM TO BE SOLVED: To provide a versatile antenna unit that can be tuned to a wideband frequency and is applicable even if a supply voltage differs. SOLUTION: The antenna unit 1 is a module, where a chip antenna 2 is packaged onto an antenna substrate 3, and is attached onto a motherboard 30 of portable radio equipment. The chip antenna 2 is composed by arranging a plurality of variable capacitive elements 7 in radiation conductors 5, 6 wound around a substrate 4 dispersively. On the antenna substrate 3, a bias circuit 11 is provided. The bias circuit 11 supplies a tuning voltage 24 based on a bias control signal (PWM signal 21) to the variable capacitive element 7 for changing a capacitive value. In the bias circuit 11, there are a DC/DC converter 15 for boosting a supply voltage to a fixed operating voltage continuously, a FET switch circuit 16 for modulating the PWM signal 21 to a boosted bias signal 23, and the like, and the boosted bias signal 23 is smoothed for generating a tuning voltage 24. COPYRIGHT: (C)2008,JPO&INPIT
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