Contents I. Introduction
Modern communication systems have an increasingly highly demand for signal frequency accuracy and stability, thus frequency synthesis technology has been come out. Direct digital frequency synthesis technology is the third generation of frequency synthesis technology, after the direct frequency synthesis technology and phase-locked frequency synthesizer technology [1]. DDS was firstly proposed in 1971 by American scholar J.Tierney, it is a new frequency synthesis principle which is based on all-digital technology, starting from the concept of phase and directly synthesis waveform required [2]. In recent years, DDS is increasingly revealing some performances that are better than those of the traditional frequency synthesizer technology, such as high-resolution, short frequency switching time, low phase noise and so on, which, made it becomes the leader of modern frequency synthesis technology.
