锁相环环路滤波器噪声特性分析与仿真

为估计环路滤波器对锁相频率合成器输出相位噪声的贡献，建立了一种常用的有源差分环路滤波器噪声模型，并推导出滤波器中各噪声源贡献的噪声的理论公式。针对一实际滤波器贡献的相位噪声进行理论计算，考虑了滤波器中运放的非理想特性后，对滤波器中各个噪声源贡献的相位噪声进行了仿真。通过理论结果和仿真结果对比，得出理论公式对实际环路滤波器噪声进行了很好的估计。最后给出环路滤波器设计时在噪声性能方面的考虑。

Noise Analysis and Simulation of PLL Loop Filter

It is necessary to accurate phase noise prediction of synthesizer for loop filterls contribution, a noise model for loop filter that is used for differential output phase detector is built, and theoretical formula Of the output phase noise contribution from each noise source in loop filter is derived. Theoretical value of phase noise is calculated aimed at the contribution from a actual loop filter, and the phase noise is simulated after considered the actual character of op-amp. Comparing the theoretical value and simulated value, the noise of the actual loop filter can be estimated by theoretical formula, and some considerations of loop filter design about the noise performance are provided.