在深空跟踪情况下,锁相环路的输入信噪比很低,通常环路噪声带宽必须做得很窄。此时热噪声的影响固然削弱,但压控振荡器的内部噪声却明显增加,必须予以重视。本文推导了二阶环和三阶环中压控振荡器内部噪声所引起的输出相位误差的计算公式,并综合了国外学者在这方面的研究成果。 In the case of deep space tracking, the phase-locked loop input signal to noise ratio is very low, usually the loop noise bandwidth must be done very narrow. The influence of thermal noise is weakened at this moment, but the internal noise of voltage-controlled oscillator increases obviously, must pay attention to. In this paper, the formulas for calculating the output phase error caused by the internal noise of the second-order and third-order ring VCOs are derived, and the research results by foreign scholars are summarized.