| 摘要 |
PURPOSE: A surface acoustic wave filter is provided to be capable of reducing an attenuation amount of a stop band by forming four pairs of inter digital transducer(IDT) electrodes without variation of a chip size. CONSTITUTION: A pair of first IDT electrodes(31a, 331b, 31c, 33) are formed which include an input electrode(31a) to which an electric signal is inputted, and a pair of second IDT electrodes(35, 37) are formed in parallel with the first IDT electrodes(31a, 331b, 31c, 33) so as to be spaced apart from the first IDT electrodes. A pair of third IDT electrodes(39, 41) are formed in parallel with the second IDT electrodes(35, 37) so as to be spaced apart from the second IDT electrodes. A pair of fourth IDT electrodes(43, 45a, 45b, 45c) are formed and include an output electrode(45a) for detecting that the input electric signal is converted into mechanical energy so as to generate acoustic wave. The fourth IDT electrodes are spaced apart from the third IDT electrodes. The IDT electrodes(331b, 31c) at both sides of the input electrode(31a) are grounded, and the IDT electrodes(45b, 45c) at both sides of the output electrode(45a) are grounded.
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