Design Of Program-controlled Signal Generator Based On DDS

In the modern research, communication system, teaching experiment and a variety of electrical measuring techniques, we often need a high precision, convertible frequency signal source, which is controlled by digital signal. It is called digital frequency synthesizer. Although frequency synthesize is not a new technique, it develops quickly in recent years. Its performance is rising and its application is wide. It is not only used in a large number of traditional fields, but also in a lot of new fields. This marks the third signal synthesize technique emerging. Direct digital frequency synthesis (DDS) includes a lot of advantages, such as tuning frequency speed quickly; highly tuning frequency resolution; tuning frequency time, phase succession, and generate agilely many kinds of signals.This paper describes the design of program-controlled signal generator based on function and feature of AD9851, which is integrated DDS device produced by American AD Company. AT89S52 is made to Single chip Microcomputer in the design, and introduces the application in direct digital frequency signal generator by AT89S52 controlled. I design the realization of hardware circuit and C language program-controlled which are based on these. Moreover, I have finished the realization of software design based on function of program-controlled signal source. The overall thinking of program-controlled signal generator's design is described in the paper. The hardware circuit design is made up of keyboard-controlled circuit, frequency-displayed circuit and the hardware design loading 40-bit frequency /phase word from AT89S52 to AD9851. It specifically describes the process of keyboard-controlled circuit and the data-transported process of frequency-displayed circuit. Moreover, the paper proposes the overall thinking of program-controlled signal generator in the C programing language. It introduces the realization of software design of keyboard-controlled circuit, frequency-displayed circuit and loading 40-bit frequency /phase word from AT89S52 to AD9851.From the perspective of the real working effects that of the hardware experiment design and software program design, the program-controlled signal generator not only is reliable and effective; but also changs frequency-speed quickly. This output wave of program-controlled signal generator is satisfied with the demand of high stability, high precision, high-resolution; and it has some characters, such as low price, small size. AD9851's output wave can reach several decemmillion Hz.