复旦大学：《微电子学与固体电子学》教学资源（硕士士学位论文）低相位噪声的数控晶体振荡器设计.pdf

I 目录摘要 ···········································································································III Abstract·····································································································V 第一章概述······························································································1 1.1 研究目的 ························································································1 1.2 研究内容及贡献 ·············································································2 1.3 论文组织结构·················································································3 参考文献 ·······························································································3 第二章晶体振荡器概述············································································5 2.1 晶体特性 ························································································5 2.1.1 压电特性 ·············································································5 2.1.2 电学等效模型 ······································································6 2.2 晶体振荡器分析方法和结构····························································8 2.2.1 晶体振荡器分析方法····························································8 2.2.2 CMOS 晶体振荡器结构 ·····················································10 2.3 晶体振荡器指标 ···········································································12 2.3.1 功耗···················································································12 2.3.2 频率稳定度········································································14 2.3.3 其他···················································································15 2.4 本章小结 ······················································································15 参考文献 ·····························································································16 第三章 Santos 结构晶体振荡器分析······················································17 3.1 核心电路 ······················································································17 3.2 线性分析 ······················································································18 3.2.1 起振时间及时间常数··························································18 3.2.2 临界跨导和牵引系数··························································19 3.2.3 小信号电压幅度·································································23 3.3 非线性分析···················································································24 3.3.1 大信号模型········································································24 3.3.2 大信号电压幅度·································································27 3.4 相位噪声分析···············································································29 3.5 设计流程 ······················································································31 参考文献 ·····························································································31 第四章 Santos 结构晶体振荡器电路设计···············································33

II 4.1 设计考虑 ······················································································33 4.2 自动幅度控制电路设计·································································35 4.2.1 晶振核心电路设计 ·····························································35 4.2.2 电流源···············································································37 4.2.3 峰值检测和比较器电路······················································39 4.2.4 自动幅度控制 ····································································40 4.3 自动频率控制···············································································43 4.3.1 数控开关电容阵列 ·····························································44 4.3.2 电容阵列的单元设计··························································46 4.3.3 一阶 delta-sigma 调制器····················································50 4.4 晶振输出缓冲级设计 ····································································51 参考文献 ·····························································································53 第五章芯片实现及测试··········································································55 5.1 芯片实现 ······················································································55 5.2 芯片测试结果···············································································56 参考文献 ·····························································································61 第六章总结与展望 ·················································································63 6.1 总结 ·····························································································63 6.2 展望 ·····························································································63 参考文献 ·····························································································63 致谢 ··········································································································65

摘要近年来，无线通信技术高速发展，对低成本、高精度、低噪声和集成化晶体振荡器的需求迅猛增长。全集成的片上数控晶体振荡器(Digitally Controlled Crystal Oscillator,.以下简称DCXO),借助射频基站发送的频率校正信号而产生的自动频率控制(Automatic Frequency Control,以下简称AFC)信号直接控制电容阵列，克服频率随温度和时间的漂移，同时满足系统对频率精度的要求。因此，DCXO以其易集成和低成本具有替代昂贵的压控式温度补偿品振 Voltage Controlled Temperature Compensated Crystal Oscillator,以下简称 VCTCXO)的巨大市场潜力。本文针对DCXO的设计关键，从晶振的基本理论着手，分析了系统性能指标，对构建DCXO系统的关键电路展开了详细的研究与设计。首先，介绍国内外研究现状，提出了数控晶体振荡器相比传统的 TCXONCTCXO所具有的优势，以及实现DCXO的设计难点。为实现设计目标，概述了几种晶体振荡器的结构，分析各自的优缺点。在研究中，探讨了晶体谐振器的等效电路及衡量晶振性能的各项指标，分析了电路的理想与非理想特性。在此基础上，设计了基于Santos结构的晶振电路，给出了电路在起振阶段的小信号分析和大信号稳态分析。对大信号情况下，振荡幅度，晶体参数，偏置电流和器件尺寸之间的关系给出了量化的模型。电路引入了自动幅度控制来平衡相位噪声和功耗。数控电容阵列的设计采用14位的分段译码电容阵列，加入了一阶delta-sigma调制器来获得高精度的频率调谐。最后，给出电路的流片测试结果。测试结果表明：DCXO芯片面积0.5 mm×0.8mm,功耗为1.8mW。DCXO振荡在25MHz时，在频偏为1kHz 和10kHz处的相位噪声分别为-139dBc/Hz和-151dBc/Hz。频率可调范围约为35ppm,频率调谐精度0.04ppm。在温度-40℃~+80℃内，频率变化±7 ppm. 关键词：数控晶体振荡器，温度补偿式晶体振荡器，相位噪声，自动幅度控制， delta-sigma调制器，电源推动中图分类号：TN432 本论文工作受到国家自然科学基金资助（项目编号：60876019）

III 摘要近年来，无线通信技术高速发展，对低成本、高精度、低噪声和集成化晶体振荡器的需求迅猛增长。全集成的片上数控晶体振荡器(Digitally Controlled Crystal Oscillator，以下简称 DCXO)，借助射频基站发送的频率校正信号而产生的自动频率控制(Automatic Frequency Control，以下简称 AFC)信号直接控制电容阵列，克服频率随温度和时间的漂移，同时满足系统对频率精度的要求。因此，DCXO 以其易集成和低成本具有替代昂贵的压控式温度补偿晶振 (Voltage Controlled Temperature Compensated Crystal Oscillator，以下简称 VCTCXO)的巨大市场潜力。本文针对 DCXO 的设计关键，从晶振的基本理论着手，分析了系统性能指标，对构建 DCXO 系统的关键电路展开了详细的研究与设计。首先，介绍国内外研究现状，提出了数控晶体振荡器相比传统的 TCXO/VCTCXO 所具有的优势，以及实现 DCXO 的设计难点。为实现设计目标，概述了几种晶体振荡器的结构，分析各自的优缺点。在研究中，探讨了晶体谐振器的等效电路及衡量晶振性能的各项指标，分析了电路的理想与非理想特性。在此基础上，设计了基于 Santos 结构的晶振电路，给出了电路在起振阶段的小信号分析和大信号稳态分析。对大信号情况下，振荡幅度，晶体参数，偏置电流和器件尺寸之间的关系给出了量化的模型。电路引入了自动幅度控制来平衡相位噪声和功耗。数控电容阵列的设计采用 14 位的分段译码电容阵列，加入了一阶 delta-sigma 调制器来获得高精度的频率调谐。最后，给出电路的流片测试结果。测试结果表明：DCXO 芯片面积 0.5 mm×0.8 mm，功耗为 1.8 mW。DCXO 振荡在 25 MHz 时，在频偏为 1 kHz 和 10 kHz 处的相位噪声分别为−139 dBc/Hz 和−151 dBc/Hz。频率可调范围约为 35 ppm，频率调谐精度 0.04 ppm。在温度−40 ℃~+80 ℃内，频率变化±7 ppm。关键词：数控晶体振荡器，温度补偿式晶体振荡器，相位噪声，自动幅度控制， delta-sigma 调制器，电源推动中图分类号：TN432 本论文工作受到国家自然科学基金资助(项目编号：60876019)