Concatenated Dds Low Spurious Research

Direct Digital Synthesis (DDS) is one of the methods of frequency synthesis technology. Due to small frequency step, fast frequency switching, low phase noise, easy to functional extension and many other advantages, DDS becomes one of the key components in many modern electronic systems and is widely used in variety of communication systems. However, DDS is a full digital structure, which leads to low frequency, narrow absolute frequency coverage, and large spurious with its output. These are the main factors that restraint the further development and application of the traditional DDS's. Single DDS synthesis technology can not satisfy the requirements of large bandwidth and small spurious. How to expand DDS's frequency bandwidth and decrease its spurious has become a difficult and hot topic for research.Firstly, DDS system architecture, technical specifications, performance advantages and the main components of the system and working principle is analyzed and studied. Second, the DDS spurious and phase noise generation mechanisms were analyzed and traditional methods of deceasing single DDS spurious and phase noise were briefly described. Third, based on the cascade DDS's phase noise and spurious improvement mechanism, this paper analyzes parallel DDS'characteristics, and analyzes cascade DDS technology which can lower the spur of DDS's outpu t was proposed. Finally, Verified by simulation and testing method of combining, in the FPGA hardware and software validation platform and commercial DDS chip verification system, the traditional single DDS and cascade DDS output phase noise and spurious suppression characteristics were simulated and tested. Simulation and test verification results show that the cascade DDS can significantly improve the output of DDS spurious performance, validating the cascade DDS low spurious technical feasibility.