| 摘要 |
PURPOSE:To obtain an excellent frequency characteristic by arranging continuously an even number or equivalent of interdigital electrodes of the same polarity longer than nearly a half of an electrode aperture length to a position where the interdigital electrode has a small crossing width so as to prevent the generation of an unnecessary elastic surface wave. CONSTITUTION:An even number of equivalent of interdigital electrodes of a polarity whose electrode length A is longer than nearly a half of the electrode aperture length W are arranged continuously, the interdigital electrode groups 8, 8' crosses on one side interdigital electrodes 9a, 9a' of the other polarity and are not crossed with interdigital electrodes 9b, 9b' on the other side. Then, a delta function train is obtained, where the delta functions of the same polarity are arranged adjacently, and since no unnecessary elastic surface wave is generated, an elastic surface wave device having an excellent frequency characteristic is obtained. The width of the interdigital electrodes of the reed screen electrode is 1/4 of the wavelength of the elastic surface wave in the example shown in figure and the interdigital electrode groups 8, 8' have a width occupied by two conventional interdigital electrodes, and when the width of interdigital electrodes is 1/8 of the wavelength, the interdigital electrode groups 14, 15 and 14', 15 have a width occupied by normal interdigital electrodes. |
