| 摘要 |
PROBLEM TO BE SOLVED: To obtain low-impedance wide-band characteristics by connecting two surface acoustic wave resonators, having three different longitudinal modes excited, in parallel, matching the resonance mode on the highest band side of one resonator with the resonance mode on the lowest band of the other, and using >=4 resonance modes. SOLUTION: The low-band and high-band resonators 10 and 11 are constituted by 400 electrodes each for input and output IDTs 12 and 13 and 200 electrodes for grating reflectors 14 on a piezoelectric substrate 15 formed of ST-cut crystal, and each have three resonance mode. The resonance by multipath reflection between the input IDT 12 and output IDT 13 on the highest band of the low- band resonator 10 and the resonance by mutlipath reflection between grating reflectors 14 on the lowest band of the high-band resonator 11 match each other on a frequency axis. Then characteristics of 0.22% in specific bandwidth and 400Ωin impedance are obtained.
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