| 摘要 |
PURPOSE:To obtain stably always the trap attenuation being the severest to the effect of a spurious wave by selecting the thickness of a substrate of a surface acoustic wave device so as to satisfy a prescribed relation. CONSTITUTION:An input electrode 2 and an output electrode 3 are provided on an Li2B4O7X-cut substrate 1 having a plate thickness (t) to constitute a surface acoustic wave device. In the device, in order to avoid the effect of a spurious wave due to the resonance in the broadwise direction onto the trap attenuation, the correlation between the plate thickness and the trap attenuation is obtained and the optimum thickness to a desired frequency is obtained, then it turns out that the effect of the spurious wave due to the broadwise resonance is minimized when the plate thickness (t) satisfies equation of 2.37Xn/t<t<[2.37X(n+2)]/f, where (n) is an odd number, (f) is the trap frequency of the filter pass band and (t) is the thickness of the Li2B4O7 plate. Thus, the surface acoustic wave device eliminating any spurious wave is obtained by using the substrate 1 having a plate thickness satisfying the said equation.
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