| 摘要 |
PROBLEM TO BE SOLVED: To provide a compact thin film piezoelectric filter with a function of an unbalance-balance converter wherein the steepness of the attenuation characteristic in the vicinity of the pass band is excellent. SOLUTION: The unbalance-balance conversion filter (thin film piezoelectric filter) is characterized by including an unbalance circuit and a balance circuit each comprising series resonators and parallel resonators connected in a ladder form, the unbalance circuit is a 2-terminal pair circuit network including a first input terminal, a second input terminal, a first output terminal, and a second output terminal, and the balance circuit is a 2-terminal pair circuit network including a third input terminal, a fourth input terminal, a third output terminal, and a fourth output terminal, wherein the first output terminal is connected to the third input terminal, the second output terminal is connected to the fourth input terminal, and the second input terminal and the second output terminal are connected to a ground terminal. COPYRIGHT: (C)2008,JPO&INPIT
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