The Pratical Signal Generator Based On DDS

Function signal generator is often used in electronic domain andlaboratory,and it also have a wide range of appications in teaching,research, manufacture and remote telemetry areas. With the development ofscience and technology,more and more requires are set on signal sourcesuch as higher frequency resolution,wider the frequency range,higherfrequency spectrum purity and so on. However, function signal generatorsused in scientific research institutes and schools have many defects such asthe low frequency accuracy and low resolution，frequency band narrow anda small number kinds of output waveform,and these traditional methodscannot satisfy the request. The emerge of high signal source based on DDSmake it possible.DDS was first advanced in1970s. The full digital DDS technique hassuch advantage as high frequency resolution,fast frequency switchingspeed,low phase noise and high stability,overcomes the shortcomings oftraditional analog signal sources， and is the main content on signalgenerator research. This design uses the AD9850chip of the AD Inc. asthe DDS model kernel and the AT89S52chip of the ATMEL Inc. as thecontrol core,and use the touch panel to input and display data.Experimentsshow that the design out put frequency bandwidth can be achieved1Hz～10MHz, and a high degree of frequency accuracy and stability.Firstly,the thesis described the history and development of frequencysynthesis techniques,analyze several principles of frequencysynthesizer,and discuss the advantages And defects of these frequencysynthesis techniques,and the design of high-presision signal source basedon DDS was given.Then described the principle of DDS including theintroduction of the composition and structure of DDS,and also themathematical analysis、spectrum analysis and spurious analysis of DDS.Themethod of spur suppression for DDS is also given in this paper.The overall design of the signal source system is behind. It includemain chips on the System selected,and the overall hardware and softwaresystem design were descriped.Detailed hardware design mainly introducedthe design of hardware modulars,such as the power supply module， touch panel module control module of AT89S52， signal output of AD9850. Thenmeasured and analyzed the output waveform data,and the improvementprogram for the signal source system. Finally summed up the work of thedissertation,and made some suggestion for further work.