一种数字波形合成失真度的计算方法及实验验证

Calculation Method for Total Harmonic Distortion of Digital Sinusoidal Waveform and its Experimental Verification

数字正弦波形是可时间量化和幅值量化的周期波形,利用数字波形合成技术生成的正弦波存在着波形失真,其失真度(THD)大小既与正弦函数一个周期内的离散点数M有关,也与数模转换器(DAC)的分辨率(即DAC的位数)N有关。本文在时域分析的基础上,通过详细的公式推导,给出了数字正弦波的失真度THD与M和N的计算公式。同时以16位高速DAC芯片LTC1597为例,利用自搭建的D/A测试系统对其进行测试,从实验的角度分析了用于数字波形合成的D/A转换器的分辨率、建立时间等特性对于数字合成正弦波形失真度的综合影响,并列表给出实验验证结果。本文的计算方法还可用于谐波分析。

Digital sinusoidal waveform is a periodic waveform, whose amplitude and time are quantified. The total harmonic distortion （THD） exists in a sinusoidal wave generated by digital waveform synthesis technique, and it depends on not only the number of discrete points in a period but also the resolution of the digital-to-analog converter （DAC）. We propose in this paper a theoretical formula in time-domain representing the relationship of the number of discrete points, the DAC resolution and the THD. Through introducing a 16-bit high speed chip ＂LTC1597 DAC＂ into a D/A test system designed by ourselves, This paper analyzed the influences of the DAC resolution, settling time and etc. on the THD of sinusoidal waves generated by digital waveform synthesis techniques and give experimental results. The novel method presented in this paper can also be applied to harmonic analysis.