DDS信号源的研制

Direct Digital High-frequency Synthesis

直接数字频率合成──ＤＤＳ是七十年代出现的一种新颖、独特的频率合成技术，它以良好的频率分辨率和快速、连续的变频性能而受到人们的关注。本文将ＤＤＳ技术与计算机相结合，介绍了一种具有较好性能价格比的微机ＤＤＳ信号源。本信号源采用的是Ｔｉｅｒｎｅｙ结构，通过相位幅值图来得到所需信号。为了简化硬件结构，采用了相位截断等数据压缩技术，并努力使装置以微机插卡形式来完成信号合成任务，为仪器及计算机功能的进一步开发留出了空间。若稍加改进，即可得到任意波形输出，应用于仪表、测控等许多领域。

Direct Digital Frequency Synthesis is an indispensable technique for generating reference frequencies whenever extremely precise frequency resolution and fast switching speed are reguired in this paper,a DDFS system drived by a computer will be presented. We use a periodically overflowing 2's complement phase accumulator to generate and store phase information and use a ROM based look up table to compute the sine function, it produce a linearly digital value each 1/Fc seconds. Especially,by using data compression technique,we reduce a Large ROM to a small size.