| 摘要 |
PURPOSE:To prevent a ground electrode and a signal-side electrode from being short-circuited with each other by making said two electrodes symmetrical with respect to the center axis in the longitudinal direction of a piezoelectric plate, and cutting off the both end parts of the signal-side electrode. CONSTITUTION:The signal-side electrode 1 is provided on one surface of the piezoelectric plate 7, and the both end parts of the electrode 1 are cut off for equal lengths L1, L2 from the end surfaces 7a, 7b of the plate 7. This length is set at the necessary minimum for preventing the shortcircuiting to the ground electrode 2. The ground electrode 2 is so provided on the other surface of the piezoelectric plate 7 that electrode 2 is turned to reach the end surfaces 7a, 7b of the plate 7. In such a way, the signal-side electrode 1 and the ground electrode 2 are formed symmetrically with respect to y-axis in the longitudinal direction of the piezoelectric plate 7. As a result, the shortcircuit between the ground electrode and the signal electrode can be prevented. Furthermore, the directional characteristic can be improved without reducing the size of the opening.
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