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本文介绍一种利用带有梳状晶体滤波器的频率引导设备实现锁相环路频率捕获的一种方法。它与锁相环的VCXO、混频器构成一自动频率微调环路。采用这种方法,频率捕获时间短,在一定程度内可以防止边带错锁。根据这一原理设计的频率引导设备,引导精度高,并且降低了对部件的要求,大大地简化了调试工作量。文中还分析了该设备产生引导误差的原因,并进行了简单的估算。最后对“等效鉴频斜率”的选取和影响引导灵敏度的原因进行了分析。本文给出了有关实验结果。
This article describes a method using a frequency-guided device with a comb-shaped crystal filter to capture the PLL frequency. It and the phase-locked loop VCXO, mixer form an automatic frequency fine-tuning loop. Using this method, the frequency capture time is short, to a certain extent, to prevent side-lock error. The frequency-guided device designed according to this principle leads to high precision and reduces the requirements on the components, which greatly simplifies the debugging work. The article also analyzes the reasons for the equipment to guide errors, and a simple estimate. Finally, the selection of “equivalent frequency discrimination slope” and the reasons that affect the sensitivity of guidance are analyzed. This article gives the experimental results.