锁相环相位噪声与环路带宽的关系分析

Relationship Analysis between PLL Phase Noise and PLL Bandwidth

应用电荷泵锁相环系统的等效噪声模型,分析电荷泵锁相环相位噪声在不同频率段的功率谱密度。据此得到相位噪声的功率谱密度与频率关系的模拟曲线。分析与模拟的结论指出环路噪声具有低通特性,而VCO噪声在低频区衰减明显,在设计锁相环路时需要综合考虑环路和VCO两种噪声的影响,然后才能确定环路带宽。该结论对于电荷泵锁相环的相位噪声与环路带宽设计具有一定的参考意义。

This paper analyzes the power spectrum density of different frequencies on charge- pump PLL phase noise by applying PLL system equivalent noise model,which has gained the simulation curve of the relationship between the phase noise power spectral density and the frequency. The conclusion points out that loop noise has low passing feature and VCO noise obviously declines in low frequency,and considers both loop noise and VCO noise when designing PLL, then PLL bandwidth can be defined. That conclusion has a certain reference sense for charge - pump PLL phase noise and loop bandwidth design.