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The Shaughnessy Report: What’s the Frequency, Kenneth?

I’ve been fascinated with antennas since I was 5 years old. I remember my parents directing me to bend our rabbit ears hither and yon until we got a clearer picture of “Laugh-In.” I remember thinking, “How does this thing push a signal into space?”

Now, many PCB designers are finding themselves pondering the same question while designing for radio frequency (RF) boards for wireless applications. Once a small but steady percentage of all PCB designs, RF is becoming more commonplace in this segment. The last few decades have brought on a proliferation of wireless handheld devices, and almost all feature some type of RF circuitry.

RF is increasingly cited in Design007 Magazine surveys as an area of concern. There’s no room for error at these speeds, and RF designers must make constant tradeoffs throughout the design process.

Antennas are an entire discipline within RF. When should you design your own antenna, and when should you use a commercial off-the-shelf antenna instead? Just as importantly, how do you avoid creating accidental antennas?

DFM is more critical than ever. Certain components must be placed in a way that isolates their noise from the other potential “victim” components. Speaking of “victims,” wireless devices often include multiple RF points, which will interfere with each other if designers are not careful. Even a simple trace on an RF board isn’t so simple.

Designers often find themselves adding extra vias to create “via shielding” to cut down on crosstalk on RF transmission lines. These vias resemble fences that surround the entire length of the RF trace. Another handy via trick is “via stitching,” which involves linking together large areas of copper on multiple layers, which helps designers avoid long return loops and impedance issues.

Material selection is a huge part of RF PCB design. Thermal conductivity is a real concern, and designers must choose a high-frequency material that meets design requirements, and hopefully without overconstraining the board and driving costs sky-high.

Some of you are thinking, “I’m not an RF designer. Do I really need to care about this?” You bet your sweet bippy! Even if you’re not working with RF yet, you’re likely designing high-speed PCBs. Chances are that you’re encountering the same challenges that your RF brethren have been dealing with for years. If you’re lucky, you might learn a few things from their (expensive) mistakes.

In this month's Design007 Magazine, our expert contributors will discuss the best practices for designing RF PCBs for wireless communications, and the many trade-offs involved, from material selection to board-level design techniques, and much more.

We start off with a conversation with IPC design instructor Kris Moyer, who discusses some of the many critical decisions that RF designers must consider. Columnist John Watson focuses on some of the many unique details that a designer faces in the wireless realm. Cadence’s Cody Stetzel provides a variety of tips for RF layout and antenna design. Columnist Barry Olney discusses best practices for controlling electromagnetic fields in wireless applications, as well as the theory behind it all. Keysight’s How-Siang Yap explains a variety of methods to defeat two of
the biggest villains in RF: interference and signal loss. And columnist John Coonrod explains how to take your thermal management skills to the next level when designing PCBs for wireless products.

We also have columns from our regular contributors Matt Stevenson and Joe Fjelstad, as well as another installment of Anaya Vardya’s DFM101 series. And this month, we begin with Part I of a three-part series on DFM for flex and rigid-flex authored by Mark Gallant of DownStream Technologies.

We’ll see you next month…and that’s the truth.

This column originally appeared in the April 2023 issue of Design007 Magazine.