| 摘要 |
PROBLEM TO BE SOLVED: To provide a variable filter using a resonator which produces an amount of suppression on an out-of-band high frequency side.SOLUTION: The variable filter using the resonator including a first coupling section and a second coupling section comprising transmission lines includes: a variable capacitance circuit having one end connected between the first coupling section and the second coupling section and the other end short-circuited; a first series resonance circuit having one end connected between the first coupling section and the second coupling section and the other end short-circuited; a second series resonance circuit having one end connected to a first input/output terminal connected to the side of the first coupling section opposite to the second coupling section, and the other end short-circuited; and a third series resonance circuit having one end connected to a second input/output terminal connected to the side of the second coupling section opposite to the first coupling section, and the other end short-circuited. |
