杭州电子科技大学
硕士学位论文
姓名：李小荣杭州电子科技大学
申请学位级别：硕士
专业：电路与系统
指导教师：王健
20100201
摘要
现代电子产品正朝着高速、高集成度和高可靠性的方向发展。带宽高达百MHz甚至GHz 的高速运放与高速数模转换器在视频处理、信号采集、实时检测等电路中的应用越来越多；边沿速率达ps级的高速数字器件已相当普遍。相应地，高速数模混合电路板（Printed Circuit Board，PCB）成为电路板发展的新趋势。高
速数模混合PCB具有新的特点，传统的PCB设计方法已不能满足需求，这类PCB设计面临着新的挑战，要求采取新的设计方法和手段，来保证产品设计的首件成功率。
信号完整性(signal Integrity，简称SI)是指信号在互连线上的传输质量。在一个高速互连系统中，信号流经芯片内部连线、芯片封装、PCB布线通道、焊盘、过孔等，任何信号传输路径都有可能引发信号完整性问题，本论文把问题主要集中在板级互连上。高速系统中，PCB 上高速信号间的互连不再是畅通和透明的，高速的互连线对系统的影响已不能被简单忽略。互连引起的信号完整性问题可能会导致系统工作不稳定，甚至不能正常工作。如何处理由高速互连线引起的信号完整性问题，是现代高速混合电路PCB设计能否成功的关键。信号完整性设计需要贯穿于整个项目设计的各个阶段，需要在设计阶段尽早地解决潜在的问题。
本论文基于高频效应、传输线理论、电磁干扰理论，对反射、串扰、同步开关噪声(SSN)、电磁干扰(EMI)等信号完整性问题进行深入分析，根据理论分析与实际经验给出各种相应问题的解决方法。笔者通过对一块高速数据采集卡进行信号完整性分析与PCB设计，主要从优化高速模拟电路PCB和高速数字电路PCB的信号完整性出发，来确保各部分的信号质量并减小数模之间的干扰，从而探索出高速数模混合PCB的设计方法和设计流程。笔者运用Cadence Allegro PCB SI与Ansoft SIwave/Designer SI仿真工具，对采集卡中的关键网络与整板进行仿真分析，通过对高速数字电路中的反射、串扰、同步开关噪声、传导与辐射等进行仿真分析来优化干扰源和干扰途径。根据仿真分析的结果制定相关布局、布线规
则来驱动设计，并在布线后对PCB进行仿真验证和设计优化，确保在设计阶段采取有效的措施来增强信号完整性，达到良好的设计效果。这也进一步证明了高速设计的仿真分析和设计方法的重要性。
本文所提出的基于信号完整性仿真分析与验证的高速混合PCB设计方法和流程，可以提高实际的PCB设计质量，降低设计风险，减小设计修改和制作的次数，从而缩短市场开发周期、减少开发成本。对于实际工作中的设计观念、设计流程及设计手段的改进与完善具有现实指导意义。
关键词：高速混合PCB，信号完整性，同步开关噪声，电磁干扰，PCB仿真
ABSTRACT
Modern electronic products are towards higher speed, higher integration and higher reliability.
The bandwidth of high-speed amplifiers and analog-to-digital converters is above hundreds MHz, even GHz.These high-speed analog devices are more and more widely used in video signal processing, signal acquisition and real-time detecting circuits. The high-speed digital devices with edge rate up to ps level are quite common. Accordingly, High-speed digital-analog hybrid circuit PCB become the new trend of PCB,which has new features. The traditional design methods can not meet the demands. The design of high-speed hybrid circuit PCB is facing new challenges. It’s necessary to take new design methods and steps to ensure the first product successful.
Signal integrity refers to the signal quality in interconnecting lines. In a high-speed interconnected system, signal flows through chip’s internal wires, chip’s packages, PCB wires, pads,
via stubs. Any transmitting paths maybe produce signal integrity problems. The paper mainly focuses on the problems in interconnecting lines. The interconnection among high-speed signal is
no longer unblocked and transparent. Its influence can not be neglected. The signal integrity problems could make system instable or malfunctioned. It is a key performance index for any successful high-speed PCB design to properly deal with the problems such as reflection, crosstalk, synchronous switching noise, and electromagnetic interference. A sound signal integrity design should run through all phases of the whole project, and the potential problems should be solved at early stage as soon as possible.
Based on high-frequency effect,transmission line theory and electromagnetic interference theory,the signal integrity problems are analyzed thoroughly in the paper,which include reflection, crosstalk, synchronous switching noise, and electromagnetic interference. Various corresponding solutions for these problems are discussed. The author analyzed signal integrity of an high-speed data sampling and signal processing mainboard in an analytical instrument and designed the printed circuit board.Mai
nly through improving the PCB signal integrity of high-speed digital circuits and high-speed analog circuits，the noise between digital circuits and analog circuits was reduced and
the whole board’s quality was ensured. Signal integrity design process with the software of Cadence Allegro PCB SI and Ansoft SIwave/Designer SI were also introduced. In order to optimize EMI sources and coupling paths,the simulations for key nets and the whole board contained termination strategy, crosstalk, resonance of the power and ground planes, synchronous switching noise,conduction and radiation analysis. The results of simulation are helpful to establish relevant design constraints for PCB layout and routing. Post-simulation is employed to verify signal
integrity and effective measures can be adopted to improve the PCB performance in design phase and to achieve better quality. This further indicates it is indispensable to adopt emulational analysis in high-speed PCB design.
The high-speed hybrid PCB design method and process based on emulational analysis for signal integrity given in this paper can improve design quality, reduce the risk of failure or repeated design, shorten design period and cut down costs. This also perfects the concepts, steps and means of the high-speed hybrid PCB design.
Key words: High-Speed Digital-Analog Hybrid PCB，Signal integrity，Synchronous Switching Noise，Electromagnetic Interference，PCB Simulation
杭州电子科技大学
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