This paper introduces the theory of the phase-locked loop (PLL) and the direct digital synthesis (DDS) , a method to improve the precision of DDS and reduce its phase truncation error is also given.

• 介绍了锁相环(PLL)技术和直接数字式频率合成(DDS)技术的基本工作原理,给出了一种提高DDS输出频率精度及减小其相位截断误差的方法。