| 摘要 |
PURPOSE:To change only the selectivity with small sized configuration without changing band width by providing a resonance line and three tuning circuits of the same structure whose capacitance is connected to the cut part of the line and arranging the tuning circuits in different directions. CONSTITUTION:The tuning circuits 1, 2, 3 are constituted by providing U-shaped resonance circuits 4, 5, 6, capacitors 10, 11, 12 connected to the cut parts 9, 8, 7 and connecting external connection terminals 15, 16 respectively to one end of the cut parts 9, 7 via capacitors 13, 14. The tuning circuits are of the same structure. An optional side of the resonance lines 4, 5 is opposed to each other, a line 20 whose one end is connected to an earth electrode 17 is formed between the opposed sides, and the circuits 2, 3 are constituted similarly. The circuits 1-3 are arranged in a line and the cut parts 9, 8 and 8, 7 are arranged in a way that the indirections differ by 90 deg. from each other. Thus, the insertion loss is reduced in the circuits 20, 21 and the filter is constituted by using the resonance lines whose length is 1/4lambda or below.
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