| 摘要 |
PURPOSE:To obtain an elastic surface wave device which decreases the ripple within the frequency effective band and increasing the attenuation at the end of the frequency band by providing the area changed into the linear form at part of the side of the piezoelectric substrate which is parallel to the propagation direction of the elastic surface wave. CONSTITUTION:Input and output electrodes 22 and 23 for propagation of the elastic surface wave are provided to piezoelectric substrate 21 made of the ceramics, crystal and the like. Absorber 24 is provided outside electrodes 22 and 23 to absorb the surface wave, and the incident surface of the elastic surface wave features the saw- tooth shape at the output side. At the input side, absorber 24 is provided for the partial absorption of the surface wave at dummy part 25 of the electrode. Thus the elastic surface wave device is obtained. Substrate 21 is shaped so that the area whose shape varies linearly may be secured at part of sides 27 and 28 parallel to the propagation direction of the surface wave, for example, shape 29 projected outside is secured for side 27. While linearly cut-off shape 30 is secured at side 28. Otherwise shape 40 formed by cutting off the both sides linearly. In such way, the ripple can be reduced within the effective band, also increasing the attenuation sufficiently at the end of the frequency band. |
