Fundamentals

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As insatiable data needs continue to grow due to artificial intelligence demands, the adoption of PAM4 standard has paved the way for future PAM-level encoding schemes to address future bandwidth limitations, prolonging the life of copper interconnect.

As circuits shrink and bit rates increase, achieving acceptable signal integrity (SI) requires experience and creativity. It calls for foresight in layout planning to keep signal paths short, which helps minimize interference between closely spaced circuits. Circuit materials must support electrical and mechanical design specifications, and components must be selected for optimum size and placement. All these factors combine to create many challenges when developing an HSD PCB.

Crosstalk in PCB and packaging interconnects is arguably one of the most complicated phenomena that may cause signal degradation. Crosstalk effects can be treated statistically as a deterministic jitter with a bounded distribution, but the distribution is usually not known. A direct analysis of a worst-case crosstalk scenario may lead to a system overdesign. Neglecting it in design may cause a system failure that is difficult to find and fix later in a design process. Distortions caused by crosstalk cannot be corrected by signal conditioning techniques at a receiver side. It is very important to understand the sources of crosstalk, how to quantify it and how to mitigate it efficiently, as Yuriy Shlepnev demonstrates in this installation of the "How Interconnects Work" series.

Successfully designing a PCB with more than one impedance while maintaining a manufacturable and economical product can be a difficult challenge. By examining the histories and uses of various impedances, Lee Ritchey simplifies the process and discusses the ideal impedance for PCB stackup design.

In a tribute to Bob Pease, David Banas explores the concept of unbounded jitter and how it aligns with the concerns of engineers and link designers. In his discussion of the definition, constituents, and practical limits of jitter, Banas embodies the simplistic approach of his hero. 

Modeling and measurement of digital serial interconnects is usually done in the frequency domain. That means that the minimal and maximal frequencies (or bandwidth) should be defined even before the analysis or measurement begins. This post introduces a simple and practical way to identify the bandwidth with a numerical analysis of defects in a single bit (SBR) or single symbol response (SSR).

This fundamentals piece looks at the digital applications of a coax cable, such as in testing USB4 implementations, with a focus on one pair of coax cables to highlight measuring some of their digitally oriented parameters not always considered on an RF based datasheet. 

Ever wonder how much energy is required to transmit data and why so much power is dissipated into heat? SIJ EAB member Yuriy Shlepnev takes a closer look.

Understanding a few simple power integrity (PI) fundamentals can go a long way towards increasing design margins when delivering power to high-speed digital loads. In this piece, Heidi Barnes provides some fundamental lessons on impedance.

Stefaan Sercu, Samtec Signal Integrity R&D Engineer, recently presented “Impedance Corrected De-Embedding,” which discussed the advantages of impedance corrected de-embedding over standard 2X through de-embedding, here are some highlights of his talk.