基于改进型DDS的函数发生器设计

The Design of Function Generator Based on Improved DDS

为方便地实现各种复杂波形的调频、调幅和调相功能,基于STC12C5A16S2单片机和改进型DDS设计了函数信号发生器。系统以AD9850芯片、计数器CD4024和双端口RAM为核心,用计数器寻址结构取代传统DDS中的累加式寻址结构,实现了波形数据的自动输出。通过AD9850与DAC两级控制相结合,实现了输出波形频率、幅值的步进可调。利用系统固化的标准波形表以及波表生成算法,有效地解决了相位调节与任意波形表的生成问题。实验结果表明,该系统结构紧凑、电路简单,具有输出波形任意化的特点。

To facilitate FM,AM and PM of all kinds of complex waveforms,we design this function generator based on STC12 C5A16S2 microcontroller and improved DDS.The design uses AD9850 chip,counter CD4024 and dual-port RAM as the system core and replaces the structure of accumulators addressing in traditional DDS by structure of counter addressing,in which the output of wave data can be realized automatically.System a-chieves the step adjustment of the output waveform frequency and amplitude by the application of AD9850 and DAC cascading control.The problem about phase adjustment and the generation of arbitrary waveform table has been effectively solved by making use of standard wave table in system as well as wave table generate algorithm.Test results show that such system has not only compact structure and simple circuit,but also the advantage of synthesis wave the user defined.