锁频环又称为自动频率控制（AFC）环，其利用反馈回路对输入频率变化进行调整，最后达到对频率的跟踪，广泛应用于雷达，卫星导航等领域对多普勒频率的跟踪。-Locked loop, also known as automatic frequency control (AFC) loop, the use of feedback loop to adjust the input frequency changes, and finally achieve frequency tracking is wi