锁相环路是一种能够跟踪输入信号相位的闭环自动控制系统。随着信息科学和电子技术的迅速发展，锁相环路在电子技术的各个领域得到了广泛的应用。-PLL is able to track the input signal phase of the closed-loop automatic control system. With the information science and electronic technology is developing rapidly, PLL at various areas of electronic technology has been widely used.