| 摘要 |
PURPOSE:To improve the phase characteristic against temperature and a high frequency attenuation characteristic by connecting a capacitor in parallel between output terminals of an extraction filter and making the sign of the polarity of the temperature coefficient of the temperature versus capacitance characteristic of the capacitor equal to the temperature coefficient of the temperature versus resonance frequency characteristic of a piezoelectric crystal vibrator. CONSTITUTION:A capacitor 4 is connected in parallel across the output terminal of the band pass type electromechanical timing extraction filter 1 comprising two piezoelectric crystal vibrators 2, 2 and a coupling capacitor 3 constituting a couple of arms. As the capacitor 4, the sign of the polarity of the temperature coefficient of the temperature versus static capacitance characteristic is made identical to the sign of the temperature coefficient of the temperature versus resonance frequency characteristic of the piezoelectric crystal vibrators 2, 2. Thus, the changing direction of the phase characteristic of the filter based on the capacitance change of the capacitor due to the temperature change is made opposite to the changing direction of the phase characteristic of the filter based on the characteristic change in the piezoelectric crystal vibrators 2, 2 due to the temperature change. Thus, the change in the both is cancelled together and the phase change to the temperature change is much decreased and the phase charactristic is improved.
|
