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735型晶体管一级机的调频中频放大器采用10.7兆赫陶瓷滤波器和LC双调谐回路相结合的方式,以期用较少的中放级数,获得所需的中频增益和良好的中频选择性。并兼顾通频带,又能使调试过程较简便。以下分器件和电路两个方面简单介绍。 (一)10.7兆赫陶瓷滤波器: 我们所选用的陶瓷滤波器是由上无一厂设计并试制生产的。该滤波器目前是由锆钛酸铅材料构成的压电体。为了得到比较高(10.7兆赫)的振动频率,厚度振动比径向和横向振动在振子加工工艺上容易实现。因为谐振频率与振子的几何尺寸有关,频率越高,几何尺寸越小,径向或横向振动的片子势必做得很小,难以精确控制。第二,运用“能阱理论”,缩小
The 735-transistor FM IF amplifier uses a combination of a 10.7 MHz ceramic filter and an LC double-tuned loop in order to achieve the desired IF gain and good IF selectivity with fewer stages to be placed. And take into account the passband, but also make the commissioning process easier. The following sub-components and circuits are briefly introduced in two aspects. (A) 10.7 MHz ceramic filter: The ceramic filter of our choice is designed and manufactured on a trial-production basis. The filter is currently composed of lead zirconate titanate piezoelectric material. In order to get a higher vibration frequency (10.7 MHz), the thickness vibrations are easier to achieve than the radial and transverse vibrations in the vibrator process. Because the resonant frequency is related to the geometrical dimension of the vibrator, the higher the frequency, the smaller the geometrical size, the smaller the radial or transverse vibration of the film is bound to be small and difficult to precisely control. Second, the use of “trap theory” to narrow