数字式频率合成器是频率合成器中一种重要形式。它在通信中和其他技术中得到广泛的应用,特别是在短波和超短波无线电通信中得到更加广泛的应用。频率合成器的一个重要质量指标就是输出信号的频谱纯度。本文将重点分析和计算数字式频率合成器输出信号的频谱纯度,指出影响其频谱纯度的主要因素以及与合成器环路参数的关系,最后指出了提高频谱纯度的可能方法。 Digital frequency synthesizer is an important form of frequency synthesizer. It is widely used in communications and other technologies, especially in short-wave and ultra-shortwave radio communications. An important quality indicator of a frequency synthesizer is the spectral purity of the output signal. In this paper, the spectral purity of the output signal of a digital frequency synthesizer will be analyzed and calculated. The main factors affecting its spectral purity and the relationship with the synthesizer loop parameters will be pointed out. Finally, the possible methods to improve the spectral purity will be pointed out.