| 摘要 |
PROBLEM TO BE SOLVED: To provide a surface acoustic wave filter device which has a balanced-unbalanced conversion function and an impedance conversion function, furthermore, is made to be able to reduce insertion loss in a pass band. SOLUTION: Input terminals of a first to a third longitudinal coupling-resonator type surface acoustic wave filters 11 to 13 of the acoustic wave filter device 1 are connected to an unbalanced signal terminal 5; the output terminal of the first longitudinal coupling-resonator surface acoustic wave filter 11, and a first IDT 12a as a first output terminal of the second longitudinal coupling-resonator type surface acoustic wave filter 12, are connected to a first balanced signal terminal 6; the output terminal of the third longitudinal coupling-resonator surface acoustic wave filter 13, and a third IDT 12c, as a second output terminal of the second longitudinal coupling-resonator type surface acoustic wave filter 12, are connected to a second balanced signal terminal 7; and the output signal phase to the input signal in the first longitudinal coupling-resonator type surface acoustic wave filter 11, and an output signal phase to the input signal of the third longitudinal coupling-resonator type surface acoustic wave filter 13, are different by 180°. COPYRIGHT: (C)2008,JPO&INPIT
|
