| 摘要 |
PROBLEM TO BE SOLVED: To provide an antenna circuit corresponding to multiband, capable of reducing the generation of harmonics radiated from an antenna and dealing with wide frequency band. SOLUTION: The antenna circuit includes: a wave dividing circuit disposed close to a power feed circuit and for dividing a high-frequency signal of a basic frequency band and a high-frequency signal of a high-order frequency band including a frequency higher than that of the high-frequency signal; a variable matching circuit connected to between the wave dividing circuit and the antenna; and a filter between the antenna and the variable matching circuit. The variable matching circuit includes a digital variable capacitance circuit disposed on a path of the high-frequency signal of the basic frequency band. The digital variable capacitance circuit is formed by connecting a plurality of capacitor units in parallel, the capacitor units each formed by connecting a capacitive element and a transistor in series, imparts bits of control data to a gate of the transistor of each capacitor unit to control ON/OFF, and changes the synthesized capacitance of the variable capacity circuit to make variable the resonant frequency of the antenna. COPYRIGHT: (C)2011,JPO&INPIT |
