【作者】 胡悦；

【导师】 周健军；

【作者基本信息】 上海交通大学 ， 电路与系统， 2008， 硕士

【摘要】 本文对于采用delta-sigma调制的小数频率合成器(Δ-ΣPLL)的建模与仿真方式进行了深入的讨论。所涉及的模型分为两个部分,线性模型和行为级模型。本文首先对混合信号系统的传输函数形式进行了讨论。在已有的连续和离散信号处理理论的基础之上,加以综合,推导出了一个明确的混合信号系统传输函数表达式,适用于实际应用中的锁相环(PLL)、延迟环(MDLL)等混合信号系统。随后对二阶电荷泵锁相环的线性模型进行了介绍,尤其对其中的鉴频鉴相器(PFD)时域和频域模型进行着重论述,运用了相关领域的仿真方式,在数学上证明了基于何种假设可以得到一个PFD的线性频域模型。并对其中的近似程度做了讨论。论文的其余部分基于作者编写的一套PLL辅助设计软件,对于其动态分析与行为级模型进行了论述。动态分析运用前述的混合信号系统传输函数表达式以及线性建模结果,得到一个二阶Δ-Σ电荷泵PLL的系统传输函数。讨论了其系统参数确定方法以及稳定时间和噪声特性优化方法。最后关于行为级模型,作者运用Matlab编写了一套二阶Δ-Σ电荷泵PLL行为级模型,进行工作周期级(Cycle-wise)的行为级仿真。能够对于锁相环中的电荷泵、压控振荡器以及delta-sigma调制器的非线性行为做出描述,得到准确的时域稳定时间分析曲线。更多还原

【Abstract】 In this work, the modeling and simulation approaches of delta-sigma fractional-n (Δ-ΣPLL) frequency synthesizer is closely discussed, including two different field of models: linearized modeling and behavior modeling.One expression of transfer function for mixed signal system is firstly proposed in this work, based on discrete time and continuous time signal processing theory, which could be employed on the study and analysis on the practical mixed-signal system, such as PLL and MDLLSecondly the linearized model of a second order charge pump PLL is discussed. And the focus is on the linearized model of PFD module, some approaches is adopted for arriving at a mathematic deduction for the linearized process based on several definite assumption. Further, the extent of approximation is discussed.The rest part of this work is based on one set of PLL design assistant toolbox developed by the author, and is focus on the dynamics analysis and behavior modeling of 2nd orderΔ-ΣPLL. The dynamics analysis is based on the foregoing mixed signal system transfer function expression and linearized modeling approaches, obtaining the system transfer function of a 2nd orderΔ-ΣPLL. Hence, the methodology of system specs, parameters calculation and optimization of settling time and noise performance, is discussed.Finally, the behavior model proposed in this work, is developed in Matlab, which could perform cycle-wise behavior simulation of a 2nd orderΔ-ΣPLL. The nonlinearity of charge pump, VCO and SDM is covered by this model, which results in a accurate settling time simulation.更多还原