| 摘要 |
PURPOSE:To adjust frequency response characteristics, delay time characteristics and the like easily, by sticking a metallic film on the back side of substrate opposed to the part including the transmission path of waves and a transducer and changing the film thickness. CONSTITUTION:On the back side of a substrate 10 opposed to the part including the transmission path of waves and transducers 11, 12, a metallic film 13 is stuck. Thus, when the film thickness of the film 13 is 1,000Angstrom , the attenuation characteristics are as shown in solid lines and when 2,000Angstrom , as dotted lines, that is, not so much change for the attenuation characteristics is caused, and only the center frequency is changed. Thus, the frequency adnustment which is very difficult for the surface waves can be made easy. |
