Based On Dds Technology Of Fpga-low Stray

Presented the concept of Direct Digital Synthesis (DDS) technology sparked a revolution in the field of frequency synthesis. The unique way of realization brings it much superiority that other frequency synthesis can not match. For example:short time of frequency switching,high frequency resolution,continuous phase change,easy-to achieve a variety of modulated signals, etc. These superiorityes make DDS widely application in communication systems, radar, electronic warfare, instrumentation, etc.At the same time,the all-digital structure of DDS also brings large spurious and output bandwidth limited defect, which limits the further application of DDS.In recent years, a large number of scholars put forward many DDS spurious suppression methods based on a large number of theoretical research and .have achieved some results. However, the shortcomings of large spurious have not yet been fully resolved.so it is important to study DDS technology and propose better solutions. Firstly,this paper describes the development of frequency synthesis technology,the basic principle of DDS and its characteristics, then phase truncation spurious and quantization spurious are discussed from a mathematical point. Then the spectrum of spur is analysed on a variety of different situations by Matlab. Then, a series of programs as mixed dynamic injection method, delay superposition and ROM table compression technology which reduces the spurious of DDS have been studied and discussed.Secondly, an improved DDS structure has been proposed and the principle of the structure is discussed in detail. Then, simulation by Matlab verifies this structure can completely eliminate the spurious caused by phase truncation.Finally, DDS is implemented using FPGA.The integrity of the hardware circuitry is built based on the output of DDS connected to the D/A converter.Then hardware circuit has been testing and analyze.