DDS合成信号的频谱杂散性分析

Spurious of Spectrum of DDS Signal

直接数字式频率合成技术作为一种全数字系统,在硬件方面具有许多优点。但是受奈奎斯特定理、自身的结构缺陷以及目前数字器件工作速度的限制,DDS输出频率较低、杂散性能不够理想,在应用上受到了一定程度的限制。对DDS进行误差分析对于提高系统性能具有重要意义。介绍直接数字频率合成技术的原理,针对相位截断误差,对DDS合成信号的频谱杂散性进行了详细的理论分析,得到采样点数N与截断部分分母M与信噪比的关系曲线,给出了定量分析结果。并结合应用实践,讨论了不同因素对信噪比的影响,提出提高信噪比的方法和思路。

The invention of Direct Digital Synthesis （DDS） is a wholly digital structure circuit with various advantages. For the limitation of digital hardware operating speed, Nyquist theorem and DDS structure,the spurious performance of DDS＇ out- put is bad and the output frequency can＇t reach a high level. Its error analysis has a great significance to improve the dynamic performance. The principle of Direct Digital Synthesizer（DDS）is introduced,the reason of DDS phase noise is analysed,the results of quantitative analysis are given,the influence of different factors on its SNR are discussed,and the way to heighten the performance is proposed.