Estimated reading time: 7 minutes

Target Condition: The Modern Masters of Signal Integrity and AI-driven Design

Signal integrity (SI) in PCB design has moved from a niche engineering concern to the defining factor in whether modern electronics succeed or fail. As data rates push beyond PAM4 (4-level 112G) gigabit territory and SerDes components exhibit edge speeds as fast as 50–100 picoseconds, PCBs behave less like collections of simple traces and more like complex electromagnetic systems.

At these speeds, a trace is no longer just a connection between two points, but a transmission structure governed by field behavior, discontinuities, and propagation delay. Even small imperfections in routing, stackup design, or return path management can lead to timing errors, signal distortion, electromagnetic interference, and, ultimately, system failure.

The Founders of Signal Integrity
I’ve compiled a list of contributors to the signal integrity evolution (see sidebar). It isn’t meant to be comprehensive; it reflects my personal recollection of experts I’ve read about or had the pleasure of meeting. I’ve loosely organized them by decade, though there is significant overlap. It is not a tidy relay race where one group hands the baton to the next.

These engineers worked concurrently, challenging, debating, and refining one another’s ideas, collectively pushing the industry (sometimes reluctantly) toward a deeper respect for physics. I struggled to organize their contributions chronologically, and that difficulty itself may mirror how AI is now learning from them faster, and perhaps with greater precision, distilling decades of human trial, error, and hard-earned intuition into algorithms.

Signal integrity did not evolve in isolation. It was built gradually over decades, drawing on insights from a diverse group of engineers who transformed abstract electromagnetic theory into a practical design discipline. They translated physics into intuition, and then into repeatable engineering practice. Today, as AI absorbs the accumulated knowledge of the field, SI is transitioning from something engineers learn through experience into something that can be partially encoded, simulated, and scaled.

Why Signal Integrity Became the Center of Modern Design
PCB design engineers have learned that, at high speeds, digital design is no longer dominated solely by logic behavior. Rather, it is by energy traveling through a physical medium. Every transition on a line is subject to reflection if impedance is not controlled. Every return current must find a path, and if that path is disrupted, it creates loop area expansion and radiated emissions. Even a via is no longer electrically transparent; it introduces frequency-dependent impedance changes that must be accounted for.

These effects are no longer “edge” cases. Engineers are realizing that they define system behavior. As a result, modern PCB failures frequently manifest not as functional design errors but as subtle physical-layer issues, such as bit errors, electromagnetic compatibility violations, degraded timing margins, or unexpected coupling between adjacent structures. In many cases, these problems are discovered late in the design cycle, making them expensive and time-consuming to resolve. This reality forced our industry to rely heavily on a group of engineers who could explain not just what was happening, but why it was happening at the physics level.

The Emergence of AI-driven SI
AI-SI is not a replacement for engineers, but a compressed, scalable extension of their expertise. It unifies signal integrity, power integrity, EMC, and manufacturability into a single system that delivers real-time design feedback.

Instead of analyzing these domains in isolation, AI-SI evaluates them together, flagging impedance issues, return path disruptions, and stackup risks during design, not after. It also links layout decisions directly to manufacturing outcomes, closing the long-standing gap between design intent and physical reality.

Its evolution is straightforward: assistant, co-designer, optimization engine, and ultimately a digital twin capable of predicting failures before a board is ever built.

The Founders of Signal Integrity
I’ve compiled a list of contributors to the signal integrity evolution (see sidebar). It isn’t meant to be comprehensive; it reflects my personal recollection of experts I’ve read about or had the pleasure of meeting. I’ve loosely organized them by decade, though there is significant overlap. It is not a tidy relay race where one group hands the baton to the next.

These engineers worked concurrently, challenging, debating, and refining one another’s ideas, collectively pushing the industry (sometimes reluctantly) toward a deeper respect for physics. I struggled to organize their contributions chronologically, and that difficulty itself may mirror how AI is now learning from them faster, and perhaps with greater precision, distilling decades of human trial, error, and hard-earned intuition into algorithms.

Conclusion
Across generations, engineers have clarified how currents truly behave, validated theory through measurement, and translated complex electromagnetics into practical design rules. They also elevated power integrity into a core discipline, forming the foundation for modern high-speed systems.

Now, AI is entering signal integrity, scaling decades of accumulated knowledge into faster analysis and design iteration. But AI didn’t invent this body of work. Every model, rule, and insight traces back to engineers who discovered, tested, and refined these principles in the real world. We can automate the knowledge, but not the gratitude.

The Modern Masters of Signal Integrity (in the U.S.)

Early Foundations (1980s–mid-1990s)

These individuals helped define SI before it was widely formalized.

Ralph Morrison

Ralph Morrison established many foundational principles that underpin modern PCB design. His work on grounding, shielding, and current flow emphasized that electrical behavior is fundamentally about loops and fields rather than isolated conductors. Morrison’s teachings clarified that ground is not a physical destination but a reference system, and that shielding effectiveness is entirely dependent on how currents are controlled and returned. These ideas are now so embedded in engineering practice that they are often repeated as rules of thumb without attribution to their origin. He died in 2019.

Howard Johnson

One of the earliest and most influential figures in this transformation was Howard Johnson. When many engineers still viewed digital signals as idealized voltage transitions moving through perfect wires, Johnson reframed the entire mental model. He insisted that high-speed digital signals must be understood as electromagnetic waves traveling through a transmission medium. His work, most notably High-Speed Digital Design: A Handbook of Black Magic, helped engineers recognize that reflections, impedance discontinuities, and propagation delays are not secondary effects but fundamental design constraints.

Both Morrison’s grounding in electromagnetic principles and Johnson’s early work translating high-speed behavior into practical PCB design rules laid the intellectual foundation for SI as a discipline.

Formalization and Expansion (mid-1990s–2000s)

This group brought SI into mainstream engineering practice through books, seminars, and early EDA alignment. This era marks the explosion of SI education: Design rules became teachable, measurable, and repeatable.

Lee Ritchey

While foundational thinkers established the physics, engineers like Lee Ritchey brought structure and repeatability to real-world design. Ritchey’s philosophy, developed through decades of consulting and training at the Speeding Edge, is grounded in the belief that system success is determined early in the design process. In his view, stackup planning and architectural decisions made at the beginning of a project dictate signal integrity outcomes more than any later routing optimization. His “right-the-first-time” approach has influenced countless high-speed designs by emphasizing prevention rather than correction.

Doug Brooks

Doug Brooks has contributed extensively to education in PCB design and electromagnetic compatibility. Through decades of teaching and writing, he has helped engineers understand the behavior of currents in practical PCB structures. His work consistently emphasizes clarity and accessibility, translating complex electromagnetic interactions into actionable design guidance that engineers can apply immediately.

Eric Bogatin

Building on this shift in thinking, Eric Bogatin expanded the discipline into a measurement-driven science. Through his work in industry and academia, including Bell Labs, Sun Microsystems, and the University of Colorado Boulder, Bogatin emphasizes that intuition alone is insufficient without validation. His philosophy centers on the idea that engineers do not design signals themselves, but rather design for the behavior of energy in a system. His teaching style, which blends theory with experimental validation, has become a cornerstone of modern signal integrity education.

Industry Scaling and Power Integrity Era (2000s–early 2010s)

The focus expanded from signals alone to full-system behavior, including power distribution.

Istvan Novak

Istvan Novak has played a central role in defining modern power integrity as a foundational discipline that directly impacts signal integrity. His work demonstrates that without a stable and well-designed power distribution network, even the most carefully routed signals will fail to perform reliably. His contributions have helped formalize decoupling strategies, PDN design methodologies, and noise analysis techniques that are now standard practice in high-speed systems.

Larry Smith

Larry Smith contributes to this ecosystem through modeling and simulation methodologies that allow engineers to predict behavior before fabrication. By applying SPICE-based analysis, IBIS models, and transmission line theory, he helps engineers understand how interconnect structures will behave under real operating conditions. His work enables a shift from reactive debugging to predictive design validation.

Mike Resso

Mike Resso similarly bridges the gap between theoretical models and physical behavior through advanced measurement techniques. His work with S-parameters, de-embedding, and time-domain analysis allows engineers to extract meaningful insight from complex interconnect systems. By connecting RF measurement rigor with digital design challenges, he ensures that theoretical models remain grounded in physical reality.

These experts pushed SI into the realm of power integrity, measurement, and compliance, especially as data rates and edge speeds accelerated.

Modern High-Speed and Application-Focused Era (2010s–present)

These voices dominate current conferences, real-world design training, and emerging applications. They emphasize practical implementation, layout discipline, EMI control, and translating SI theory into designs that pass the first time, especially in today’s dense, high-speed systems.

Rick Hartley

Rick Hartley has contributed another critical layer of understanding by focusing on the relationship between signal integrity and electromagnetic compatibility. His teaching consistently reinforces that signal quality is not defined solely by the trace itself, but by the integrity of the return path. By translating electromagnetic theory into practical layout guidance, Hartley helped engineers understand that current does not simply travel forward, it completes a loop, and that loop defines the system’s electromagnetic behavior.

Daniel Beeker

Daniel Beeker adds a more visual and intuitive dimension to this understanding by demonstrating that signal integrity is fundamentally about electromagnetic space. Through live demonstrations, he reinforces that signals do not exist solely in copper traces, but in the fields surrounding them. His perspective helps engineers move beyond schematic thinking into spatial electromagnetic awareness.

Ken Wyatt

Ken Wyatt is a highly respected independent consultant, instructor, and author in the field of electromagnetic compatibility (EMC) and electromagnetic interference (EMI). Often referred to as “The EMC Doctor,” he is known for helping engineers diagnose and fix noise problems early in the design process. His work emphasizes hands-on troubleshooting, practical pre-compliance testing, and effective PCB design practices to prevent issues before they reach the lab.

Karen Burnham

As signal integrity matured, validation became as important as design. Karen Burnham represents this shift toward measurement-first engineering. Her work emphasizes that simulation alone cannot guarantee performance, and that confidence in a design must ultimately be earned through measurement and validation. In her view, verification is not a final step but an integral part of the design process itself.

Stepping back, the pattern seems clear:

• Morrison and Johnson taught us why signals misbehave 
• Ritchey, Brooks, and Bogatin taught us how to design around it 
• Novak, Smith, and Resso taught us you can’t ignore power anymore 
• Hartley, Beeker, Wyatt, and Burnham are showing us how to actually get it right in today’s designs 

This column originally appeared in the May 2026 issue of I-Connect007 Magazine.