| 摘要 |
PURPOSE:To improve the selectivity of a single frequency by setting a maximum cross width of an interdigital electrode on a specific piezoelectric substrate so as to give a specific value with respect to a wavelength thereby improving the no load Q. CONSTITUTION:At least a couple of interdigital electrodes are provided on a piezoelectric substrate of shear horizontal type made of a 30-50 deg. rotation Y axis-cut LiNbO3 single crystal on which a surface acoustic wave is propagated and the maximum cross width WMAX of the interdigital electrode is selected to be 2<=WMAX/lambdaIDT<=10 with respect to the wavelength lambdaIDT. In setting the maximum cross width WMAX of the interdigital electrode to the said range, the no load Q is increased and the selectivity of a single frequency is improved. Thus, in applying the method to, e.g., a surface acoustic wave resonator for VCO, the C/N ratio as the VCO is improved. In order to the higher no load Q, it is preferred that the maximum cross width WMAX of the interdigital electrode is set to be 2<=WMAX/lambdaIDT<=8.
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