The Design And Implementation Of DDS Based On FPGA

After development for over eighyt years,the frequency synthesis technology whichwas born in the1930s has gradually become the important applications in aerospace,lelemetn und telecommand, communications, radar and other aspccts’.l’he DOS (DirectDigital Frequency Synthesis) which was born in the1970s is not onh thethird-generation digital frequency synthesis technology but also having a pure digitalsiructure. C om pared with ihe traditional frequency synthesis techno logy a he directdigital frequency synthesis (DDS) technology has lots of advantages such as highresolution of output frequency.low and continuous noise of output phasc.short time ofIrcqucncy switching,wide bandwidth of the output frequencv,small volume and lowpower consumption and so on.It is an important method of frequency synthesis.In thispaper, the issues about spurious and precision of the output signal spectrum of thedirect digital Jrequency synthesis (DDS) have been researched.For the issue of theDDS spurious.it will propose several improvement measures on the basis of analyzingthe noise characteristics of the output signal spectrum.For ihc issue of the DDSprecisionjt will propose a type of ROM compression algorithm based on the Taylorlinear interpolation technique, rhen.it will constitute a new DDS structure to realizeDDS function.When the logic resources in FPGA is insufficient.it will save ihc ROMresources and improve the precision of output signal by compressing the data.The main research work of this paper is as follows:Firstly, having an o\crvic\\about the basic principles、advantages and disad\a-ntuges of several common frequency synthesizer teclmology.lt mainly introduces thedirect digital frequency synthesis(DDS) in engineering applications.Then having a listand comparatixe analysis of their pcribmiance.Then having a detailed presentation ofthe currcnt research situation and development trend of DDS technology at home andabroad.Secondly.having a detailed analysis of the basic principle, the basic structure and the output spectrum of DDS technology.With regard to the system synthesis spectrum.itdiscusses the spectral analysis on the condition of the ideal and the actual situation.Thirdly,the paper analyzes the spurious issue of the DDS. It will propose severalimprovement measures on the basis of analyzing the noise characteristics of the outputsignal spectrum. In order to improve precision of the DDS output signal,due to theinsufficient ROM logic resources in FPGAJt will propose a type of ROM compressionalgorithm based on the Taylor linear interpolation technique,Then,it will constitute anew DDS structure to realize DDS function.lt will save the ROM resources andimprove output precision by compressing the data.Fourthly,discussing how to conduct programming design for each module of DDSsystem by using the Quartus II12.1which is the FPGA software development tool ofAltera company and the VHDL language which is the mainstream hardware descriptionlanguage.Atfer successful compilation,using Modelsim-Altera10.1b which is thesimulation sotfware tool to conduct waveform simulation.Then,using the developmentboard DE2-70of FPGA and the embedded SignalTap II logic analyzer of Quartus II12.1to realize the online real-time debugging of DDS system.At last.it will achieve theexpected expeirmental results.