| 摘要 |
PURPOSE:To prevent the occurrence of ripple for a double mode piezoelectric oscillator when it is formed into a BPF, by connecting an exciting electrode on the other main surface of a piezoelectric plate which has an oblique symmetrical relation to an exciting electrode on a main surface of the piezoelectric plate to a common terminal and at the same time connecting other exciting electrodes to an input or output terminal. CONSTITUTION:An exciting electrode 17 on the upper surface of an AT-cut quartz plate 16 and an exciting electrode 20 on the rear surface which is obliquely symmetrical to the electrode 17 are connected to a common terminal 29 through lead-out electrodes 21 and 22 plus a metallic supporting plate 35. An exciting electrode 19 and an exciting electrode 18 which is obliquely symmetrical to the electrode 19 are connected to an input terminal 28 or an output terminal 30 through lead-out electrodes 23 and 24 plus metallic supporting plates 34 and 33. An intermediate electrode pair of 25 and 26 are used to give an fine adjustment to the coupling coefficient K among exciting electrode pairs. A cascade connection is secured between such two double mode piezoelectric oscillators to form a BPF. With use of this BPF, the variance is eliminated within a pass band, and at the same time the degree of ripple can be set at <=0.5db. |
