Signal Integrity Journal

PAM2 vs. PAM4 Signaling: Simply Explained

Tue, 07 Jan 2025 00:00:00 -0500

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 interconnects.

Planning PCB Layouts for High-Speed Digital Signals

Fri, 09 Feb 2024 09:41:05 -0500

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.

How Interconnects Work: Anatomy of Crosstalk

Tue, 06 Feb 2024 00:00:01 -0500

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.

Why Making All Transmission Lines in a PCB 50 Ohms is Good Technological Practice

Fri, 14 Apr 2023 00:00:22 -0400

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.

What’s All This About Unbounded Jitter, Anyway?

Tue, 11 Apr 2023 05:00:00 -0400

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.

How Interconnects Work: Bandwidth for Modeling and Measurements

Tue, 12 Apr 2022 00:00:00 -0400

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).

RF to Digital: Extreme Coaxial Cable Requirements

Thu, 07 Apr 2022 00:00:00 -0400

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.

How Interconnects Work: Absorption, Dissipation and Dispersion

Tue, 15 Mar 2022 00:00:00 -0400

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.

Power Integrity Fundamentals: Impedance vs. Frequency

Thu, 06 May 2021 00:00:00 -0400

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.

Impedance Corrected De-Embedding Verifies Connector Performance

Tue, 06 Apr 2021 00:00:00 -0400

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.

DDR5 Signal Integrity Fundamentals

Tue, 19 Jan 2021 00:00:00 -0500

The most notable difference between DDR5 and previous generations is the introduction of decision feedback equalization, a technique used in serial link systems to improve the integrity of received signals. In the wake of the new technology, this short article outlines some of the fundamental signal integrity concepts in the context of DDR5.

Millimeter Waves Technologies and Challenges for EMC & Wireless

Tue, 17 Nov 2020 00:00:00 -0500

The extension of operating frequencies in the mmWave region and beyond is the story of wireless development for the next thirty years. Understanding the resulting challenges and improving the state-of-the-art is a key driver for the EMC and wireless Industries. This article takes a look at some of the fundamentals of mmWave, including signal propagation, available spectrum, and challenges and issues facing EMC.

Miniature Bulkhead EMI Filters for Aerospace Applications

Tue, 06 Oct 2020 00:00:00 -0400

Component manufacturers continue to develop increasingly miniaturized bulkhead filter capacitors that also offer increased current capacity, voltage, and operating temperature ranges. This post looks at the details of this miniaturization in order to help aerospace systems designers satisfy stringent size and weight constraints and further improve system performance.

What is Differential Impedance and Why do We Care?

Tue, 14 Apr 2020 00:00:00 -0400

We care about maintaining the same differential impedance for the same reason we care about maintaining the same instantaneous impedance of a single-ended (SE) transmission line: to avoid reflections. SIJ’s EAB member Bert Simonovich explains the fundamentals and why it matters.

Evaluating & Designing Around Specification Requirements

Thu, 06 Feb 2020 00:00:00 -0500

Watch out for those operating frequencies. Here are some tips to avoid EMC emission test failures.

4 Things to Look For When Interpreting Standard Requirements

Mon, 20 Jan 2020 00:00:00 -0500

Here are some tips to prepare for a standards audit and avoid being assessed a deficiency.

Introduction to Signal Integrity Analysis

Tue, 10 Dec 2019 00:00:00 -0500

This article lays out the basics of signal integrity problems, explains s-parameters, and identifies challenges in high-speed design.

Coming Up: Easier Signal Integrity Simulation Setup with IBIS 7.0

Tue, 11 Jun 2019 00:00:00 -0400

There was a time when the signal integrity of connections between digital ICs could be nearly ensured by following one simple rule: don’t connect more than some maximum number of input pins to any single output pin. Often the fanout limit would be around 7. No models, no simulations. Everything we needed was in the thick books of vendor datasheets that filled our shelves, the tree-killing viral precursor to AOL installation CDs. Ah, those were the days!

Seven Habits of Successful 2-Layer Board Designers

Tue, 23 Apr 2019 00:00:00 -0400

If performance matters, if the interconnects are not transparent, or if you want to develop good habits, you will want to incorporate these seven habits in your next two layer board design.

PCI Express Gen5 is Coming: What You Need to Know for Tx Measurements

Tue, 19 Feb 2019 00:00:00 -0500

While we all love increased network speed, there is an implied assumption that the backbone speeds of the internet will keep up with this rising demand placed upon it by millions of new 5G devices. PCIe 5.0 (or Gen5) represents the technology that is needed by the computer, data center, and ultimately the 5G wireless industry to enable the next generation of mobile and desktop applications. So, what is PCI Express 5.0 and how does it compare to PCI 4.0? Read on to find out.

Far-field Emissions from PCB Cavities

Thu, 31 Jan 2019 00:00:00 -0500

In high-speed circuit designs, power integrity (PI) and electromagnetic interference (EMI) are connected together. When the edge of the cavity created by power (PWR) and ground (GND) planes in PCBs radiates, the peak frequencies in the emissions are the same as the peak frequencies in the cavity self-impedance.

Shielding and Filtering Are Not Independent of One Another

Tue, 21 Aug 2018 00:00:00 -0400

I have lost count of the number of times I have been asked to fix an EMC problem, only to find that a shielding box has been designed or purchased to provide XdB up to fMAX. Or a filter has been designed or purchased with a similar specification, but to reduce cost the filter has been mounted on a printed circuit board (PCB) inside the box, with a cable from it entering or exiting the box through a plain connector.

Impedance: The Most Confusing Term in Signal Integrity

Mon, 09 Jul 2018 00:00:00 -0400

In more than 30 years of teaching signal integrity, I find the most confusing topic for engineers, even those working in the field for years, is the question of what is the impedance of a transmission line? Read on to learn about the 5 types of impedance.

Back to Basics: Bandwidth and Rise Time

Mon, 14 May 2018 00:00:00 -0400

Eric Bogatin explains the figures of merit in the time and frequency domain, and he steps through how to get a rough measure of the highest frequency components in a signal.

Life beyond 10 Gbps: Localize or Fail!

Wed, 18 Apr 2018 00:00:00 -0400

Yuiry Shelpnev argues that simulating a link in isolation from the rest of the board (localization) is probably the most important requirement to simulate interconnects predictably. Read on to understand this important concept.

Moving from 28 Gbps NRZ to 56 Gbps PAM-4 - is it "free lunch"?

Mon, 02 Apr 2018 00:00:00 -0400

If we know how to design interconnects that correlate with the measurements for 28 Gbps NRZ, is it going to be a "free lunch" to move to 56 Gbps NRZ? Not so easily, as I learned recently. Read on to see how you can benefit from some analysis and validating your tools.

The Signal Integrity Perils of Power Via Stubs

Wed, 14 Mar 2018 00:00:00 -0400

We are usually not worried about having via stubs on power and ground planes and shapes. Does it mean they are completely harmless? When it comes to potential damage to high-speed signals, power-via stubs can be almost equally as bad as signal-via stubs. Here is how and why.

Signal Integrity Basics: Technical Terms

Mon, 26 Feb 2018 00:00:00 -0500

Nyquist frequency, first harmonic, clock frequency, fundamental frequency, and some other intimidating terms might be thrown at you by an SI engineer. Read on to get up to speed on these and other terms you need to know.

A Tale of the Equations That Changed Everything

Wed, 21 Feb 2018 00:00:00 -0500

When I first started studying Maxwell’s Equations, I was always intrigued by its mathematical finesse. How could someone think of that? Today we take them for granted and we sometimes forget how amazing they are and what a genius the guy was. In my view, James Maxwell should be with, if not above, Einstein and Newton among the greatest physicists to ever live, but outside our field people seldom know who Maxwell was.