| 摘要 |
PURPOSE:To reduce the effect of reflection on an end face as well as the size of a chip, by selecting the angle formed by the direction of a reflecting end face of an acoustic wave and the direction vertical to the propagating direction of the acoustic wave so that a prescribed relation is satisfied between the maximum opening length of an electrode and the acoustic wavelength. CONSTITUTION:The angle formed by the end surface AB of a substrate and the direction vertical to the propagating direction of an acoustic wave is set at theta, and the maximum opening length between electrodes 1 and 2 is set at W. The wave going to the face AB among the acoustic waves produced from the electrode is reflected between P and Q and travels backward toward the electrode. The reflected wave has an angle of 2theta to the incident wave. When the equiphase surface is referred to as RS at a certain time point of the reflected wave made incident to the electrode, the angle formed by the direction of an electrode finger and the surface RS is set at 2theta. The intersection between the lower termination of an excited acoustic wave and the surface RS is set at T, and an intersection H is formed between a line led from the point T and parallel to the propagating direction of the excited acoustic wave and a line led from R and parallel to the direction of the electrode finger. If the TH is set at >=1/2 wavelength lambda, the effect of the reflected wave is reduced less than the case of theta=0. Therefore the effect of the reflection on the end face can be reduced with a small chip size if the angle theta is set at WXtan2theta>=lambda/2. |
