What Is Signal Integrity?
什么是信号完整性
信号完整性用于衡量电信号从源传输到目标位置时的质量。它是指即使存在各种干扰时，信号也能保持预期形状和时序特征的能力。
信号完整性至关重要，因为它能够确保数据传输准确可靠，并且不受噪声、失真和反射等的不良影响。信号完整性缺失会导致数据传输错误，这可能会造成系统故障乃至重大的经济损失。
Role of Signal Integrity in System Design
关键要素：
- 布局前分析：在 PCB 布局前对高速串行和并行链路进行信号完整性分析，这有助于发现设计实现过程中可能出现的问题。
- 布局后验证：在布局后验证信号完整性，这有助于发现由布线和组件等不同因素导致的问题。
- IBIS-AMI 模型：使用模型对集成电路、内存或系统之间复杂的高速接口进行仿真。
- 信号完整性可视化：使用衰减、时序抖动和眼图等指标来衡量信号质量，并识别信号失真问题。
为了帮助了解信号完整性分析的详细信息，MathWorks 提供了一系列工具，包括 Signal Integrity Toolbox™、SerDes Toolbox™、RF PCB Toolbox™ 和 Mixed-Signal Blockset™。它们提供了从系统的布局前分析到布局后验证等一系列功能，同时可生成可视化结果，如眼图、波形图、频谱图、眼图轮廓和时钟偏移预算分析。这些工具提供了全面的方法，用于防止数据通信系统或高速电子设备出现问题。
布局前分析
要实现良好的信号完整性，一个关键步骤是进行布局前分析。这种分析通常在设计阶段完成，旨在发现潜在的问题，并帮助工程师作出明智的决策以优化设计。
Signal Integrity Toolbox 的串行链路设计器中的 OIF CEI 25G-LR 布局前原理图，用于 MATLAB。
通过执行布局前分析，工程师可以在设计周期的早期发现并解决潜在问题，从而降低后期高成本的设计修订和修改的风险。这种分析还可帮助设计人员针对信号完整性优化设计，从而使设计更加稳健可靠，且符合行业标准。
Real-World Applications
Pre-layout PCB signal integrity analysis is especially critical in industries and applications where high-speed, high-reliability communication is essential, such as:
- Data centers, where high-throughput servers rely on clean signal transmission across backplanes and interconnects
- Automotive electronics, where advanced driver-assistance systems (ADAS) and infotainment require robust high-speed communication
- High-speed memory interfaces such as DDR, LPDDR, and GDDR, where timing margins are tight and even minor distortions can cause data corruption
By integrating signal integrity simulation into the early design phase, you can ensure your systems meet performance targets and regulatory standards from the start.
Learn More About Pre-Layout Analysis
Post-Layout Verification for Ensuring PCB Signal Integrity
Post-layout verification involves reviewing the physical implementation of the design, including the actual PCB layout and routing, to ensure that it meets the expected signal integrity performance. The process involves using signal integrity simulation and analysis tools, such as Signal Integrity Toolbox™, to simulate the electrical behavior of the final design and identify any potential issues.
Printed circuit board as shown in the Signal Integrity Viewer app in Signal Integrity Toolbox. (See documentation.)
用于通道分析的 IBIS-AMI 模型
IBIS-AMI（I/O 缓冲区信息规范 - 算法建模接口）是一种建模标准，用于高速通道的布局前分析和布局后验证。IBIS-AMI 将一个信号路径内各组件的电气特性相结合，形成一个完整的通道模型，使工程师能够更准确、更高效地仿真复杂的高速数字系统。
IBIS-AMI (I/O Buffer Information Specification–Algorithmic Modeling Interface) is a modeling standard used for both pre-layout analysis and post-layout verification of high-speed channels. IBIS-AMI combines the electrical properties of individual components within a signal path to form a complete channel model, enabling you to simulate complex high-speed digital systems with greater accuracy and efficiency.
SerDes 系统的 IBIS-AMI 模型，分别显示在 Signal Integrity Toolbox、SerDes 设计器和 Simulink 中。
在布局前分析和布局后分析中使用 IBIS-AMI 模型，有助于优化设计时间，降低设计错误风险，并提升高速数字系统的整体性能。然而，创建准确可靠的 IBIS-AMI 模型可能是一个复杂而耗时的过程，需要专业技术知识和专用软件工具，如 SerDes Toolbox。
Real-World Applications
Equalization and channel modeling are critical in systems where high-speed data must travel across complex or lossy media, such as:
- Data center interconnects, where long PCB traces and cables introduce significant signal loss
- High-speed memory interfaces such as DDR, LPDDR, and GDDR, where tight timing margins demand precise signal conditioning
- Automotive Ethernet and infotainment systems, where equalization ensures reliable communication over twisted pair cables
By integrating signal integrity simulation with equalization and channel modeling, you can design systems that meet performance targets even under challenging physical constraints.
Learn More About Equalization and Channel Modeling
Compliance and Standards Verification in Signal Integrity Analysis
In the electronics industry, ensuring compliance with industry standards is a critical part of signal integrity analysis. As data rates increase and protocols become more complex, verifying that a design meets industry specifications is essential for data transmission reliability and product certification.
Using MATLAB® and Simulink®, you can perform automated compliance checks against a wide range of high-speed interface standards, including:
- PCI Express® (PCIe)
- USB 3.x and USB4®
- Optical Internetworking Forum (OIF) and IEEE 802.3 Ethernet
- DDR/LPDDR/GDDR memory interfaces
- Automotive Ethernet and MIPI® standards
These tools enable you to simulate real-world operating conditions, generate eye diagrams, and evaluate jitter, noise margins, and BER to ensure that designs meet the required thresholds. This level of signal integrity simulation helps you identify and resolve issues before hardware testing, reducing the risk of costly redesigns or compliance failures.
Real-World Applications
Compliance verification is especially important in industries where interoperability and certification are mandatory, such as:
- Consumer electronics, where devices must pass USB compliance testing to reach the market
- Automotive systems, where Ethernet and MIPI interfaces must meet strict EMI and timing standards
- Enterprise networking and storage, where PCIe and high-speed memory interfaces must deliver consistent performance under heavy data loads
By integrating compliance verification into the high-speed digital design workflow, you can ensure that your products are not only functional but also standards compliant and ready for global deployment.
Learn More About Compliance and Standards Verification
Signal Integrity Analysis Metrics and Visualizations
In high-speed digital design, signals must remain intact during transmission to achieve good signal integrity performance. Commonly used metrics and visualizations include:
- Voltage margin: The voltage margin measures the difference between the amplitude of the signal and the signal’s noise margin. The voltage margin should be sufficiently high to ensure that the signal can be reliably demodulated at the receiver.
- Timing analysis: This metric involves calculating the signal’s rise and fall times, propagation delay, and jitter. You can use timing analysis to evaluate the design’s timing budget and ensure that the signal transitions within the required timing window.
- Jitter: Jitter is the variation in the signal’s timing over time. Jitter can result from a variety of sources, including signal distortion, crosstalk, power supply noise, and attenuation. You can use jitter histograms and eye diagrams to identify and analyze jitter in high-speed digital systems.
- Eye diagram: Eye diagrams are used to analyze the signal’s performance over time and identify potential signal integrity issues. They involve plotting a graph of the signal’s amplitude against time, usually in the form of a histogram. This visualization technique provides a comprehensive view of the signal’s behavior, including jitter, noise, and timing issues.
- Bit error rate: BER calculates the number of erroneous bits in a data stream. A high BER value indicates poor signal integrity performance. You can use BER to quantify the design’s signal integrity performance then optimize the design to reduce BER.
- Attenuation: Attenuation is a measure of signal loss over distance or time. High levels of attenuation can result in signal distortion and signal failure. You can use attenuation measurements to evaluate the signal’s performance and design transmission lines and circuits to minimize attenuation.
- Crosstalk: Crosstalk occurs when one signal’s electrical field induces noise into an adjacent signal. You can use crosstalk measurements to evaluate the level of interference between channels, calculate the crosstalk coupling coefficient, and identify design methods to reduce the crosstalk level.
- Time-domain reflectometry (TDR): TDR measures the impedance of a transmission line by comparing the signal’s output with the input signal reflected from the end of the line. This technique helps to locate impedance variations and signal integrity issues along transmission lines.
- Channel operating margin (COM): COM quantifies the design’s margin between the signal’s eye and the worst-case impairments. COM helps you evaluate the design’s signal integrity performance and identify areas for improvement.
信号完整性可视化
在高速数字设计中，必须确保信号在传输过程中保持完整，才能实现良好的信号完整性性能。评估信号完整性需要用到各种指标和可视化，包括：
- 电压裕度用于度量信号振幅和信号噪声裕度之间的差异。电压裕度应足够高，才能确保信号可以在接收机处可靠地解调。
- 时序分析涉及计算信号的上升和下降时间、传播延迟和抖动。工程师利用时序分析来评估设计的时序预算，并确保信号在要求的时窗内转换。
- 抖动是信号时序随时间的变化。引起抖动的原因可能有很多，包括信号失真、串扰、电源噪声和衰减。工程师可以使用抖动直方图和眼图，识别和分析高速数字系统中的抖动。
- 眼图用于分析信号性能随时间的变化，并识别潜在的信号完整性问题。它们涉及绘制信号振幅随时间变化的图，通常采用直方图形式。这种可视化方法有助于全面了解信号的行为，包括抖动、噪声和时序问题。
- 误码率 (BER) 是用于计算数据流中的错误位数的指标。BER 值越高，信号完整性就越差。工程师可以利用 BER 来量化设计性能并优化设计。
- 衰减用于衡量信号随距离或时间变化而产生的损失。如果衰减程度高，则可能会导致信号失真和信号故障。工程师可以使用衰减测量值来评估信号的性能，并设计传输线和电路以最大限度地减少衰减。
- 串扰指一个信号的电场对相邻信号产生的噪声干扰。工程师可以使用串扰测量值来评估通道之间的干扰程度，计算串扰耦合系数，并确定降低串扰程度的设计方法。
- 时域反射技术 (TDR) 是一种用于测量传输线阻抗的分析方法。TDR 可将信号输出与传输线末端反射的输入信号进行比较。这种方法有助于确定传输线上的阻抗变化情况和信号完整性问题。
- 通道操作裕度 (COM) 用于量化设计中信号眼图与最差情形下的影响之间的裕度。COM 可帮助工程师评估设计中的信号完整性性能，并确定需要改进的地方。
波形示例，显示在 Signal Integrity Toolbox 的并行链路设计器中测量的阈值和参数。
PAM3 眼图用 Signal Integrity Toolbox 创建，显示在信号完整性查看器中。
Signal Integrity Analysis with MATLAB and Simulink
To proactively address these challenges, you can use MATLAB and Simulink for signal integrity analysis. By modeling and simulating entire systems, you can detect eye diagram closure, jitter, excessive bit error rates, and other potential issues before physical prototyping. This virtual testing enables you to design and verify equalization techniques, optimize high-speed links, and ensure overall signal quality, saving significant time and resources in the development cycle.
With MATLAB and Simulink products for signal integrity analysis, you can perform:
- Pre-layout analysis in high-speed designs: Identify and resolve potential signal integrity issues early through simulation and modeling before PCB layout begins.
- Post-layout verification: Validate real-world signal behavior and detect layout-induced problems using post-layout PCB signal integrity verification.
- Equalization and channel modeling: Design and simulate equalization strategies to mitigate signal distortion and maintain data integrity across lossy channels.
- Compliance and standards verification: Ensure your design meets industry standards such as PCIe, USB, and DDR through automated compliance testing and simulation.
Signal Integrity Toolbox, SerDes Toolbox, RF PCB Toolbox™, and Mixed-Signal Blockset™ provide features ranging from pre-layout analysis to post-layout verification of a system while producing visualizations such as eye diagrams, waveform plots, frequency spectra, eye contours, and skew budget analysis. These tools provide comprehensive means to prevent issues in data communication systems or high-speed electronics.
Learn More About Capabilities in MATLAB and Simulink
示例和操作方法
软件参考
另请参阅: SerDes Toolbox, RF PCB Toolbox, RF Toolbox, Mixed-Signal Blockset, 混合信号系统, IBIS-AMI 模型, S 参数, 卷积, 快速傅里叶变换 (FFT), Signal Integrity Toolbox, serdes
