中文摘要：

通过对直接数字合成技术DDS工作原理的分析，结合具体的DDS芯片AD9850，详细介绍了包括FM，FSK，PSK等多种数字调制方法的实现。结果表明，数字调制具有分辨率高、全数字化可编程、相位噪声低等特点。利用多路选择器连接调制信号和载波信号，可以实现多种调制信号的任意切换。

英文摘要：

Through analysis on the working principle of direct digital synthesis （DDS） technique, combined with actual DDS chip AD9850, detailed introduction to including FM, FSK, PSK etc multi-digital modulation methods＇ realization was made. The results show that digital modulation is with high resolution, total digitalization programmable, and low phase noise etc. By using multi-route selector to connect modulation signal and carrier wave signal, random switching of multi-modulation signals can he realized.