A Design Of Low Frequency Digital Programme-Controlled Signal Source

By surveying the research of the DDS knowledge, The author has proposed ascheme to design a low frequency programme-Controlled signal source which usedchip AD9850. Direct Digital Synthesis (DDS) is the third generation frequencysynthetic technique, which has the higher resolution ratio, the more quicklyfrequency conversion rate. So it has the broadly applying prospect in the electronic,Automatic and communication fields.In the paper, the principles of DDS are introduced firstly. Then the author gives abriefly introduce about chip AD9850 and AT89S51, which is the design basis to thepaper. After that, a detail analysis of the software and hardware about the singalsource is given: On the hardware, taking the chip AD9850 which controlled bysinglechip AT89S51 as core, also including filter, scope controller, and wave selectormodule, built entire system; On the software, applying LabVIEW, design theprogrammed interface about the signal source; The interaction between software andhardware is realized by serial communication, the LabVIEW procedure transmits theupdating character string by using the computer serial port. Electrical level changedby MAX232,Then singiechip AT89S51 receives the data, processes the data, and turnsit into the control word which AD9850 can identify. After that, the signal sourceproduces the signal which the user needs. Finally, The process that debugs the systemis introduced, also given out the experiment data, and carried out analysis aboutperformance of the signal source.Proven by the experiment, The DDS signal source has met the requirements for thesubjected. The signal source can be used in some dynamic measurement systems, suchas piezoelectric acceleration calibration system, ultrasonic ranging system, therebyprovides a basic for establishing a high-efficient computer-based automaticmeasurement platform. Comparing with the traditional manual signal sources, theprogramme-controlled signal source greatly improves the efficiency and reduceshuman intervention, and ensures measurement accuracy.