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96 I-CONNECT007 MAGAZINE I MAY 2026 These individuals helped define SI before it was widely formalized. Early Foundations (1980s–mid-1990s) Both Morrison's grounding in electromagnetic principles and Johnson's early work translat- ing high-speed behavior into practical PCB design rules laid the intellectual foundation for SI as a discipline. Ralph Morrison Ralph Morrison estab- lished many foundational principles that under- pin modern PCB design. His work on ground- ing, shielding, and current flow emphasized that electri- cal behavior is fundamentally about loops and fields rather than isolated conductors. Morri- son'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 embed- ded 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 digi- tal signals must be understood as electromag- netic 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 funda- mental design constraints. Formalization and Expansion (mid-1990s–2000s) This group brought SI into mainstream engi- neering practice through books, seminars, and early EDA alignment. This era marks the explo- sion of SI education: Design rules became teachable, measurable, and repeatable. Lee Ritchey While foundational think- ers established the phys- ics, engineers like Lee Ritchey brought struc- ture and repeatabil- ity to real-world design. Ritchey's philosophy, devel- oped through decades of consulting and train- ing at the Speeding Edge, is grounded in the belief that system success is determined early in the design process. In his view, stackup plan- ning and architectural decisions made at the beginning of a project dictate signal integrity outcomes more than any later routing optimi- zation. His "right-the-first-time" approach has influenced countless high-speed designs by emphasizing prevention rather than correction. Doug Brooks Doug Brooks has contrib- uted extensively to education in PCB design and electromagnetic compatibility. Through decades of teaching and The Masters of Signal Integrity TA RG E T C O N D I T I O N