数字合成周期信号的频谱及信噪比

Spectrum and signal-to-noise ratio of digitally synthesized periodic signals

数字查表法合成周期信号是一种最常用的直接数字频率合成技术。该方法若再利用小数地址序列生成技术 ,可达到很高的频率分辨率。然而 ,采用小数地址序列生成技术合成波形 ,会产生“寄生谐波”。作者采用非均匀采样周期信号谱分析方法 ,研究以查表法合成的周期信号的频谱 ,推导了合成周期信号的信噪比 ,并揭示了其一些重要的性质。这些理论 。

Digital look up table method for synthesizing periodic signals is the most popular technique for direct digital frequency synthesis. The method is capable of very high frequency resolution if the technique of fractional addressing is used. However, fractional addressing introduces undesirable spurious harmonic components. This paper applies a new digital spectrum analysis technique for nonuniformly sampled periodic signals to analyze the fine structure of the harmonic components present in digitally synthesized periodic signals using the look up table method and also derives the signal to noise ratio (SNR) in closed form. These theories provide a guide for designing and analyzing digitally synthesized signals with a specified SNR requirement.