| 摘要 |
PURPOSE: To obtain the filter comparatively small in size and capable of sufficiently suppressing the side lobes. CONSTITUTION: In this filter, a titanium diffused light waveguide 22, reed- screenlike elastic surface wave excitation electrodes 23 and an acoustic wave absorber 24 are arranged on a lithium niobate substrate 21 and a rectangular interaction region 25 is formed in a space between the electrodes 23 and the absorber 24. In this region 25, silicon membranes each having a <=1,000μm thickness are formed and the surface resistance of each of the membranes is set at a desired value so as to provide 1.3dB/cm of the attenuation constant (α) of an elastic surface wave by subjecting the membranes to annealing treatment for a prescribed period of time. Thus, the side lobes are sufficiently suppressed are therefore, the need of adopting a filter structure in which the electrodes 23 are connected in tandem can normally be eliminated.
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