Two PLLs are introduced,one has coherent detection circuit and integral scanning circuit,the other has assistant phase-comparator and scanning generator,and their merits and demerits are compared.

• 介绍了2种具有扫描捕获电路的锁相环,即具有相干检测电路和积分扫描电路的锁相环和具有辅助鉴相器和扫描发生器的锁相环,并比较了电路各自的优缺点。