直接数字频率合成器的教学实验

本文介绍一个电子系统设计实验-直接数字频率合成（DDS）信号源的设计与实现。该信号源可输出一定频率范围的正弦波、方波和三角波信号，输出频率可通过键盘进行预置，输出信号的类型和频率由LED数码管显示。实验采用单片机完成波形的相位、幅度值计算，波形数据存储在RAM中；用CPLD进行相位累加，并提供与单片机和数码管、RAM及内部累加器的接口和控制，由RAM读出的波形数据通过DAC芯片转换为模拟量，最后经一个模拟滤波器，对输出波形进行平滑。

Instructional Experiment of DDS

This paper presents an example experiment of electronic system design, which realizes a waveform generator in the way of Direct Digital Synthesis(DDS). It uses the method of software combined with hardware to realize the DDS. The output signals are sine waveform, rectangular waveform or triangular waveform with a certain frequency. The signal's type and frequency can be preset by the keyboard, and displayed by the LED of digits. In the experiment, the microcontroller is used to calculate the signal's phases and amplitudes, and the wave data is stored in RAM. A CPLD is used to accumulate phases, offer interface and control among the microcontroller LED of digits, RAM and accumulator inside the CPLD. A DAC IC is used to convert digital signal to analog signal. Then a filter is used to smooth the output signal.