Based On The Dds Precision Of The Signal Source And Research

High-accuracy signal source is essential in various testing andexperiments, which are widely applied in communication, radar,measurement, control and education. With the development of electronictechnology, more and more requires are set on signal source such as:higher frequency resolution, wider the frequency range, higher frequencyspectrum purity and so on. There are some shortages and defects aboutthe function and accuracy of the signal source which is designed bytraditional methods, and these traditional methods can't satisfy the request.In order to solve the problem, this paper designs and developshigh-accuracy and high-performance signal source based on DDS (DirectDigital Synthesis) technology.The content of this paper mainly includes the following aspects:Firstly, after researching the design method of the signal generator,the limitation of the traditional methods is analyzed and pointed out, andthe excellence of DDS technology in the signal generator designapplication is expatiated.Secondly, the basic principle and the performance characteristics ofone type of DDS chip with high cost capability is elaborated, and thischip is used to develop a signal source with frequency range from 0 to15MHz. According to the topic request, the overall design of signalsource based on the DDS technology is proposed, and the hardwaresystem is designed and developed based on DDS, and the hardwareelectric circuit of the system is given out as well. The design method andthe principle of the MCU main control module, the power module, thesample and hold module, and the A/D converse module, the low-passfilter module, input and output module, and the display module of thesystem are discussed in details.Thirdly, the paper elaborates the overall thought of software design.According to the software plan-and the union hardware electric circuit,the overall as well as several subsidiary modules of the flow chart are given out, then the corresponding program is established with MCS-51assembly language.Fourthly, the simulation test is carried on to the software debuggingresult, and the generated waveforms can be seen through the oscilloscope.Two types of waveforms with the frequency of 1MHz and 10MHz aregiven.Fifthly, this paper proposes a new researching way of DDS signalsource, which unifies the DDS technology and PLL (Phase-locked Loop)technology. The new approach can suppress the dispersion of DDS moreusefully.By experiments, the designed system can generate three signals suchas sine-wave, square wave and triangle wave, and can dynamicallydemonstrate the frequency of the generated signals and the instantaneousvoltage value of the sine-wave signal. The adjustable accuracy of thesignal frequency, phase and amplitude and the anti-interference all attainthe anticipated object basically.