关键词: 锁相环, 鉴相器, 低通滤波器, 压控振荡器

Abstract: Based on analysis of the operating mechanism of Phase-locked loop (PLL), a second-order equivalent model was established for PLL’s tracking error by use of transfer function methodology, and theoretical analysis was done regarding the dynamic frequency-and phase-tracking performance of PLL. A simulation model of PLL was constructed on MATLAB for verification, with which simulations were carried out with regard to various circumstances of input signals, such as frequency and phase step-change, continuous temporary change of frequency, harmonics distortion, etc. Both theoretical analysis and numerical simulation show that PLL renders typical behaviors similar to that of a second-order control system, which will inevitably result in response time, over-adjust and deviation, and thereby some concrete conditions are required to realize accurate tracking to input signals. The research results present valuable reference basis for application prerequisites determination, peripheral circuit parameters design and performance amelioration of PLLs.

Key words: PLL, phase detector, low-pass loop filter, voltage-controlled oscillator(VCO)