石英晶体参数测量的数字鉴相系统

System Design of Measuring Quartz Crystal by Digital Phase Discriminator

石英晶体做为高精度频率源的核心部件被广泛应用于各个领域,对于高精度的石英晶体谐振频率的测量需要进行精确稳定的相位差检测;为了提高相位差测量精度,研究了高精度的数字鉴相方法,该方法可以提高π网络零相位法的检测精度,并且在鉴相的同时实现鉴频和鉴幅,可以利用鉴频提高鉴相的精度,利用鉴幅加快π网络检测速度;为了验证数字鉴相方法的有效性,研制了基于DSP的石英晶体参数测量π网络零相位法系统,利用该系统检测石英晶体的谐振频率,检测误差达到2PPM。

It is needed to detect phase--difference accurately for measuring the resonant frequency of high--precision quartz crystal. In order to＇improve the precision of phase--difference detection, digital phase discriminator is studied in this paper. The accuracy of zero--phase detection can be real＇ized by this method. It can measure frequency and amplitude by this method. Frequency-- detec,ted can improve the pre- cise of phase--difference detection, and amplitude--detected can improve the speed of phase--difference detection, In order to verify the validity of digital phase--demodulation, a hardware system based on DSP is developed. The resonant frequency of quartz crystal is detected by this system and the detectable error is beyond 2PPM.