| 摘要 |
PURPOSE:To prevent the deterioration in characteristics such as spurious radiation of a filter and reduction in a guaranteed attenuation due to the acoustic and electromagnetic coupling, by providing penetratingly a slit between electrode pairs of a piezoelectric substrate. CONSTITUTION:The filter is constituted by attaching two sets of split electrodes 2, 3 on the surface of the piezoelectric substrate 1, providing common electrodes 5, 6 at the back side and generating the oscillation of the two modes with the respective electrode pair. Slits 20, 21 are provided penetratinly respectively between both electrode pairs 2, 3 and between both ends of the substrate 1 and the electrode pairs 2, 3. Further, the acoustic coupling between both said electrode pairs 2, 3 is blocked completely in this way. A metallic fin 26 fixed to a base 23 is stood at a position corresponding to said slit 20. Since the metallic fin 26 penetrates through the slit at the center of the substrate, the electromagnetic wave propagated between both electrodes 2, 3 or both electrode terminals 12, 13 is blocked effectively by grounding suitably the base 23. |
