| 摘要 |
PROBLEM TO BE SOLVED: To provide a band variable filter provided with band variable filter elements 3(1) to 3(3) whose pass band can be adjusted by a turning voltage, wherein the number of the band variable filter elements in use and the number of switch circuits are remarkably reduced, the manufacturing cost is low, and no large layout space is required. SOLUTION: The band variable filter used for a CATV system and connected to an up-converter for forming the TV signal of each channel (CH) from an intermediate frequency signal is provided with a first band variable filter element 3(1) for selecting the TV signal within a low channel region in all CH TV signals, a second band variable filter element 3(2) for selecting the TV signal within a mid-channel region, and a third band variable filter element 3(3) for selecting the TV signal within a high channel region. Each of the filter elements 3(1) to 3(3) has a plurality of varactor diodes whose capacitance is controlled through application of a CH selection turning voltage, adjusts the CH selection tuning voltage applied to each of the filter elements 3(1) to 3(3), and selects one channel within each channel region. COPYRIGHT: (C)2004,JPO
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