| 摘要 |
PURPOSE:To improve the temperature characteristics of a filter by securing a non-polarization state for the areas at both ends of a piezoelectric ceramic plate in its longitudinal direction together with a stepped processing part formed at the center area and keeping the vibration energy only in said processing part. CONSTITUTION:The AC voltage is applied between electrodes 11a and 11f with a grounded electrode 11d. No vibration is produced in an area I because this area is not polarized and therefore the area I serves as a mere capacitor. While the width W' of a center area III is smaller than width W of both areas II and IV and therefore the vibrating waves are transmitted only to the area III owing to an energy shut-up function. Then the temperature characteristics of the phase rotary value can be compensated at the center frequency of a filter by securing the desired temperature characteristics for both piezoelectric ceramic vibrators V1 and V2, i.e., the areas II, III and IV as well as a capacitor C1, i.e., the area I respectively.
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