锁相环中无源环路滤波器的设计与仿真

摘要

the basic performance of phase locked loop(PLL) was mainly determined by the loop filter. In order to save the simulation time and improve the design efficiency, a kind of system-level design and hybrid simulation way was applied to loop filter design based on ADS software platform. The relationship between cut-off frequency and the phase-locking speed of RC delay filter was analyzed. In order to improve the stability of PLL, the lag-lead filter structure was introduced. Furthermore, the amplitude-frequency characteristics and factors of affecting the phase margin were analyzed in the lag-lead filter. Finally, the relationship between the phase margin and the Phase-locked speed was worked out based on ADS software, which provided theory references for loop filter design.%锁相环(PLL)的基本频率特性主要是由环路滤波器决定的.为了节省锁相环的设计仿真时间,提高设计效率,提出一种基于ADS仿真平台的环路滤波器系统级设计与仿真方法.分析RC无源滤波器截止频率与锁相速度之间的关系；引入滞后超前滤波器结构,提高PLL的稳定性,还分析滞后超前滤波器的幅度-频率特性,以及影响相位返回量的因素,并基于ADS仿真平台分析相位返回量的大小与环路锁相速度之间的关系,为环路滤波器设计提供理论依据.