锁相环就是锁定相位的环路。学过自动控制原理的人都知道，这是一种典型的反馈控制电路，利用外部输入的参考信号控制环路内部振荡信号的频率和相位，实现输出信号频率对输入信号频率的自动跟踪，一般用于闭环跟踪电路。-Locked loop (phase), as the name implies, is the lock phase of the loop. Principle of automatic control of the people know, this is a typical feedback control circuit, the external input reference signal control the frequency and the phase of the oscillation signal inside the loop, the frequency of the output signal of the input signal frequency automatic tracking, generally used for closed-loop tracking circuit.