| 摘要 |
PURPOSE:To reduce size without exerting any influence on characteristics by reducing the propagation speed of a surface acoustic wave at a voice channel filter or the part of the filter and a color channel filter in comparison with that at another filter part. CONSTITUTION:On a piezoelectric substrate 1, a video channel filter consists of electrodes 101 and 102, a color channel filter of electrodes 11 and 12, and a voice channel filter of electrodes 11, and 13. The voice and color channel filters have narrow bands, so electrode size is very large. For this purpose, a film of a material, such as zinc oxide, reducing the propagation speed of a surface acoustic wave is formed at the part of a substrate 14 where the electrodes 11-13 are to be formed. As a result, the surface acoustic wave speed at the part 14 becomes less than that at the substrate 1, reducing the electrode size. Consequently, the size of a surface acoustic wave device for a separate carrier system is reduced without influencing its characteristics. |
