Best Signal Integrity Analysis Tools For PCBs

The concept of signal integrity analysis to support PCB designs could mean many things. In PCBs, multiple interfaces are used to connect components and each has different signal integrity requirements, all requiring some level of analysis. In response to the demand for better and faster analysis capabilities, the EDA software industry has stepped up with many solutions for system-level design and analysis, with several options specifically targeting signal integrity analysis tasks in PCB design.

This guide gives an overview of the various options for signal integrity analysis and their capabilities. Some of these are system-level analysis tools, while others are specialized for PCBs. Some of these software options are free or low cost, while others are more appropriate for enterprise-level users. The goal is to help you determine the best option for your design, budget, and level of expertise.

Types of Signal Integrity Analysis Software

All signal integrity software performs some type of simulation, whether it is circuit-level, directly from the PCB layout in 2D or 3D, or as linear networks with extracted simulation models. Once simulations are performed, the software automates analysis tasks that help engineers understand or prevent possible signal integrity problems in a design. Different types of analyses are possible in different software packages, and the EDA industry provides many options for signal integrity analysis.

There are many signal integrity analysis tasks that can be performed with the right software tools. Analysis typically comprises circuit analysis, linear network modeling, and system-level modeling.

Circuit Analysis

In these simulators, circuit models are designed and used to understand signal integrity, both in terms of how signals interact with components and with physical interconnects in a design. In the former case, circuit analysis is used to understand how a driving or receiving circuit either generates or interprets a signal. For drivers, the goal is to prevent distortion, while for receivers, the circuit should be able to extract data, perform measurements, or properly terminate a signal.

These are typically SPICE-based simulators, such as the following options:

• ngspice: Open-source SPICE engine supporting transient, AC, noise, and mixed-signal circuit simulations.
• LTspice: Widely used free SPICE simulator with strong support for switching regulators and analog circuits.
• Altium Designer: Includes integrated SPICE simulation directly in the schematic editor and supports multiple SPICE model formats including LTspice and PSpice models.
• QUCS: A schematic-based circuit simulator supporting AC, transient, S-parameter, and RF simulations, commonly used for analog and RF circuit development.

These tools are not normally used for full system-level signal integrity simulations. Instead, they evaluate how circuits interact with interconnects or how circuit behavior affects signal integrity across different frequency ranges. For a more comprehensive evaluation of signal integrity involving physical interconnects, we turn to EDA applications that provide linear network analysis.

Linear Network Analysis

Linear networks can be constructed from simulation models to describe full interconnect behavior from driver to receiver. These networks can be constructed from circuit models, SPICE models, or S-parameter models which describe circuit behavior. These models can constructed from equivalent circuits, full-wave electromagnetic simulations, or phenomenological models. The goal in linear network analysis is to create a cascade of individual interconnect elements (connectors, traces, vias, etc.) to build a full simulation model for analyzing signal integrity.

Many standard system-level simulation tools have linear network features built-in. These include:

• Simbeor: Supports Touchstone files and circuit models in a GUI for SI analysis
• pyBERT: An open-source Python package that supports the same analyses as other EDA tools
• CST: Includes a full-wave electromagnetic simulator and a linear network analyzer
• Ansys: Same as CST, but with some analysis and model-building tasks automated
• Keysight ADS: A popular application for signal integrity analysis in PCBs, packages, and systems
• MATLAB: Includes many specialized packages for signal integrity and RF design
• QUCS: The Quite Universal Circuit Simulator (QUCS) can use Touchstone files alongside other models to analyze signal integrity

The goal is typically to produce a standard analysis that is needed for signal integrity, such as eye diagrams, S-parameters, or transient simulation results. These simulations can be extended further with more advanced system design analysis applications, which gives a much more accurate description of system behavior.

System Design EDA Applications

System-level design tools extend the linear network analysis approach by incorporating behavioral models, digital equalization, and protocol-aware features that allow designers to evaluate full communication channels. For example, tools such as Keysight ADS can include IBIS or IBIS-AMI models for transmitter and receiver behavior, enabling simulation of equalization, jitter tolerance, and channel compliance in high-speed SerDes links. These applications are commonly used to validate channels for standards such as PCIe, Ethernet, or USB by generating S-parameters, eye diagrams, and bit error rate estimates based on realistic channel models.

Commercial and Open-Source Simulators

While signal integrity analysis tools help to analyze models extracted from simulation or measurement, a simulation application may still be needed in order to develop models used in analysis applications. For example, in cases where analyzing a proposed connector design, a simulation application can be used to extract an S-parameter model as a Touchstone file for use in an analysis application. Commercial and open-source simulators can be used to extract these models. These are summarized in the following table.

These applications also provide their own analysis capabilities as integrated features, either automated or semi-automated. In some workflows they can perform both model extraction and signal integrity analysis, although many design teams still rely on dedicated SI analysis software for channel verification and system-level validation.

Data Display and Analysis Tools for Signal Integrity

Signal integrity workflows often rely on tools that import Touchstone files (S-parameters), plot results in the time or frequency domain, and generate quick metrics like return loss, insertion loss, or eye diagrams. Commercial options like Keysight PLTS and the Touchstone editor inside HyperLynx provide these capabilities in a polished GUI, but they require paid licenses.

MATLAB is commonly used to analyze S-parameter data, generate eye diagrams, and implement custom channel simulations. For engineers seeking a free alternative, GNU Octave provides a largely compatible environment capable of running many MATLAB scripts with minimal modification. Octave is also integrated into QUCS, allowing engineers to perform advanced post-processing and data analysis directly on circuit simulation results.

S-parameter visualization in MATLAB. [Source: MathWorks]

Whether you need to build reliable power electronics or advanced digital systems, use Altium’s complete set of PCB design features and world-class CAD tools. Altium provides the world’s premier electronic product development platform, complete with the industry’s best PCB design tools and cross-disciplinary collaboration features for advanced design teams. Contact an expert at Altium today!

Frequently Asked Questions

What is the best software for signal integrity analysis?

There is no single “best” software. The correct choice depends on the level of automation needed in building simulation models and running analysis tasks. Some software gives users more control or simulation options, building models, and configuring analysis tasks.

Does PCB design software support signal integrity analysis?

Yes, PCB design software enables signal integrity analysis. This is done directly with built-in features, or indirectly by allowing exports in standard data formats for use in other simulation applications.

Can SPICE be used for signal integrity analysis in PCBs?

SPICE is normally used for circuit-level validation. It does not consider real transmission line models or interconnect models extracted from #D electromagnetic simulators, so it does not fully capture real system behavior on the PCB.

Is 3D electromagnetic simulation required for signal integrity analysis?

No, not for all analyses. In the context of signal integrity analysis, 3D electromagnetic simulation is used for direct computation of the electromagnetic field, or for extracting models for use in linear network analysis.