无相位截断情况下DDS的幅度量化杂散特性分析

Amplitude-quantization spurs in direct digital frequency synthesizers in absence of phase truncation

幅度量化是DDS的主要杂散来源之一。本文结合DDS在军用无线通信系统中的应用,对两种条件下的幅度量化杂散信号进行了严格的时域描述和频谱对比,分析了各种DDS参数对杂散特性的影响,然后着重对无相位截断情况下的幅度量化杂散信号进行了DFT分析和波形分析,推导出几个关于其频域特征和功率水平的重要结论,并通过实际DDS芯片的杂散测量结果和计算机仿真对结论进行了验证。这些结论可用于DDS工程应用中的杂散评估和参数选择,同时也可为DDS的低杂散设计提供理论依据。

Amplitude quantization is one of the main sources of spurious noise frequencies in direct digital frequency synthesizers （DDSs） , which affects the application of DDS to some communication systems. In this paper, the amplitude-quantization spurious signals in DDSs under two different conditions are exactly described in time domain and compared in frequency domain. The effects of DDS parameters on the properties of the spurious signals are studied. Then the frequency spectra of the amplitude-quantization spurious signals in absence of phase-accumulator truncation are emphatically analyzed using DFT and simulated on computer. Several important conclusions are drawn, which can provide theoretical supports for parameter selection and spurious performance evaluation in DDS applications.