| 摘要 |
PROBLEM TO BE SOLVED: To achieve miniaturization by allowing two vertically coupled multiple mode SAW filters to share one grating reflector as a grating reflector at the adjacent side. SOLUTION: IDT electrodes 2, 3, and 4 are adjacently arrayed along the propagating direction of surface waves on the main face of a piezoelectric substrate 1, and a grating reflector R1 is arranged on the left side of those IDT electrodes, and a grating reflector R2 is arranged on the right side of those IDT electrodes so that a double mode SAW filter A can be constituted. Moreover, IDT electrodes 5, 6, and 7 are arranged coaxially as the propagating direction of the surface waves on the right side of the reflector R2, and a grating reflector R3 is disposed on the right side of the IDT electrodes 5, 6, and 7 so that a double mode SAW filter B can be constituted. The reflector R2 is shared by two double mode SAW filters A and B. When the number of the grating reflectors R1, R2, and R3 is respectively defined as M1, M2, and M3(=M1), M2<2×M1.
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