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EMC BENCH NOTES

How to Use Spectrum Analyzers for EMC

By Kenneth Wyatt

spectrum analyzer measures power (default) or voltage versus frequency. Most digital harmonic emissions occur in the range 10 kHz to 1 GHz and this defines the minimum frequency range for spectrum analyzers. Some harmonics may even extend up to 3 GHz. Two types of harmonic emissions will be observed: narrowband and broadband. Many times, you’ll see a combination of the two.

Narrowband Versus Broadband

Narrowband harmonics are the most common for radiated emissions and most likely to exceed the limits. They appear as a range of narrow spikes and are usually harmonically related (multiples of a clock frequency). For example, Ethernet is usually clocked at 25 MHz, so it’s common to see harmonics every 25 MHz, sometimes exceeding 1 GHz. Figure 1 shows a series of 25 MHz clock harmonics (aqua trace). The yellow trace is the measurement noise floor.

PRACTICAL ENGINEERING

Pre-compliance for Product Safety

By Don MacArthur

MC Pre‑compliance Testing

Many articles, entire books, and chapters of books promote the benefits of performing pre-compliance electromagnetic compatibility (EMC) testing and show how easy it is to carry out bench-top EMC measurements using relatively inexpensive and homemade test apparatus.

EMC pre-compliance testing is highly beneficial. I strongly encourage doing it if you are interested in discovering EMC-related weaknesses in your design as early in the product development cycle as possible. Discovering EMC design weakness early means more and less costly solutions are available before the final design is locked down. So, the question is this: If pre-compliance activities are good for discovering EMC design weaknesses early in product development, why not apply the same thought process to product safety?

Military and Aerospace EMC

Portable Electronics Onboard Aircraft
Part 1

By Patrick André

everal times, I have talked with people in the general public about the use of electronics on aircraft, often with the same response: “There is no good reason they have us turn off our electronics.” However, those of us in the EMC industry, and especially those in the aerospace aspect of the industry, know how true the issues can be. June 8, 2011, ABC News addressed 75 possible incidents of EMI on aircraft¹. Keith Armstrong, in his “Banana Skins” series, has nearly 100 documented issues relating to aircraft. On December 12, 2020, a flight computer on Virgin Galactic SpaceShipTwo rebooted due to an EMI issue, causing an abort of the test flight. Thankfully, pilots C.J. Sturckow and Dave Mackay were not hurt and were able to glide to a safe landing.

Concerns about interference in commercial avionics date back to the late 1950s. A special committee of the RTCA, SC-88, with support of the Federal Aviation Administration (FAA), was formed to study the use of electronics by passengers. On April 12, 1963, DO-119 was published but without regulatory limits placed on the radiation emissions of portable electronic devices. However, responsibility for assuring compliance with FAR 91.21 (was FAR 91.19 at the time) remained with the operator of the aircraft.

EMI Shielding and Thermal Interface Considerations for Commercial and Defense Drone Technology

Utilizing Advanced Materials to Ensure High Performance and High Reliability for UAVs

By Sierra Meloan and Ben Nudelman

erial drones are rapidly becoming integral to modern society, dominating headlines in combat tactics and finding widespread use across various industries. From 2020 to 2030, the global drone market is anticipated to grow at a compound annual growth rate (CAGR) of 20%, with much of this expansion taking place in the segments of logistic drones, enterprise drones, and defense drones.

Advancements in drone technology accelerate the need to meet strict demands of lightweighting, electronics thermal management, and electromagnetic interference (EMI) shielding to ensure uncompromised signal integrity.

Types of Drones and Their Growing Applications

Before we talk about some engineering solutions to thermal management and EMI shielding challenges, let’s explore the scope of drones we’ll cover in this article. When we say drones, we’re referring to unmanned aerial vehicles (UAVs), which are aircraft that are meant to be operated remotely or without a human pilot on board. And while many of the examples we give will refer to drone applications, it’s important to note that the products we discuss can and are used in other drone-adjacent remote or aerial applications. This includes commercial aircraft, defense aircraft, electric aircraft, and even ground-based drone defense technology.

Navigating Mexico Electrical Safety Certification Requirements

A Guide to the Ever-Changing World of Mexico’s Electrical Safety Regulatory Compliance Requirements

By Claudia Cordon and John Grinager

n our previous article, “Navigating Mexico Certification Requirements for Radio-Telecom Devices” (see In Compliance Magazine, July 2024), we outlined Mexican approval procedures for radio and telecom products from a radio-telecom compliance perspective. Separate from radio-telecom requirements, many electronic devices are subject to electrical safety compliance requirements. Fortunately, many of the organizations and processes involved in radio compliance are the same as the ones involved in safety compliance.

In this article, we will review the requirements for three safety standards in Mexico and the processes and actors involved in demonstrating compliance with those requirements. We will also explain how to obtain import documents for devices that fall outside the scope of the three standards. Finally, we will cover an important standard that is applicable to most electronic products regarding labeling, packaging, user guides, and warranties.

Circuit Spacings: Determining Product Safety Requirements

A Guide to Identifying and Determining Safety Critical Spacings

By Maryam Mahmoodi and Jim Bender

his article provides a simplified overview of product safety-related circuit spacings and practical methods for effectively determining when critical circuit spacings requirements may apply.

Featured examples help to illustrate applications and provide awareness of alternatives and exemptions to “classic” clearance and creepage approaches, simplifying determination and, in many cases, reducing end-product footprints through smaller printed circuit boards.

Impact of Spacings to Successfully Contribute to a Safe and Compliant Product

Circuit spacings contribute, in part, to safe and compliant products. With almost no exception, end-product and/or component-level product safety standards provide requirements for printed circuit and/or component-level spacings, commonly referred to as “creepage” and “clearance,” both critical terms to understand and differentiate.

Preventing Liability from Foreign‑Made Products

How to Protect Yourself When Selling Foreign Products

By Kenneth Ross

quick look through recent 2024 recall notices posted on the website of the U.S. Consumer Product Safety Commission (CPSC) reveals that a majority of recalled products were manufactured in China.¹ And a recent analysis of 1^st quarter 2024 recalls by Sedgwick Brand Protection reveals the following products with the highest number of recalls – sports and recreation, children’s products, electronics, toys, and home appliances.² Most of these products are manufactured in China or other locations in Asia.

The Hong Kong Trade Development Council (HKTDC) analyzed recalls in 2021 and had the following conclusions:

According to information collected from the CPSC consumer product recall database, there were 155 recalls involving nearly 36 million units during January‑August 2021 that either violated mandatory standards or presented a substantial risk to the public.

Imported products accounted for approximately 85.8 percent of the recalls issued (133) and about 89.1 percent of the total number of units recalled (31.8 million) during the first eight months of the year, while U.S. products accounted for 16.1 percent of the recalls issued (25) and approximately 10.9 percent of the total number of units recalled (3.9 million).

Analysis of Transmission Lines in Sinusoidal Steady State

Different Circuit Models and Their Applications: Part 2

By Bogdan Adamczyk

his is the second of three articles discussing four different circuit models of transmission lines in sinusoidal steady state. In Part 1 [1], Model 1 and Model 2 were presented. In this article, we focus on Model 3. Model 3 is mathematically most expedient for evaluating the values of the minima and maxima of standing waves. The locations of the minima and maxima of standing waves are determined using Model 4.

Transmission Line Model 3

To present Model 3, it is helpful to recall Model 1, shown in Figure 1.

In Model 1, we are moving away from the source located at z = 0 towards the load located at z = L. Model 3, shown in Figure 2, is obtained from Model 1.

In this Model we are moving away from the source to the load, just like we did in Model 1. But in Model 3, the source is located at z = –L while the load is located at z = 0.

PRODUCT Showcase

MACHINE LEARNING APPLICATIONS IN THE NOVEL ESD COMPACT MODELING METHODOLOGY

By Wei Liang and Ahmed Ginawi for EOS/ESD Association, Inc.

Why IS ESD Compact Modeling Important

Electrostatic Discharge (ESD) is well known as one of the major reliability concerns in semiconductor manufacturing. Proper ESD protection solutions are always required to ensure integrated circuits do not fail during an ESD event. During the IC chip designing process, it is always highly desirable to have a complete set of ESD compact models of ESD protection devices that the IC designer could utilize in circuit-level SPICE simulations to achieve optimized circuit performance. It is important to predict and ensure that the ESD protection circuits and the core circuits are operating as desired, and this is key to achieving the right ESD protection solution for the first time. Therefore, the development of the ESD compact model has become one of the most essential elements in ESD device development.

What is Machine Learning?

Machine learning is a subfield of artificial intelligence (AI) that uses algorithm models to recognize the patterns in each dataset as well as learn and predict based on the supplied training dataset. It consists of a few steps, including data collection, data preparation, training, evaluation, and model tuning. Figure 1 shows the working flow of the generic machine learning concepts. Utilizing machine learning techniques will promote business success by improving time efficiency and design/prediction accuracy. In the semiconductor industry, for example, foundries are trying to apply machine learning techniques to areas like automatic defect classification, electrical tests, acoustic anomaly detection, and predictive equipment maintenance. It can also be used in EDA development, such as simulation models.

Using Near-Field Probes to Troubleshoot Radiated Immunity Failures

By Dr. Min Zhang

ur February 2024 column (refer to Reference [1], “Using a Near-Field Probe to Troubleshoot Transient Failures”) introduced a valuable technique for troubleshooting electric fast transient (EFT) failures at the PCB level. The same principle can be applied to troubleshooting radiated immunity failures. In this column, we present a case study to demonstrate these techniques.

In the following example, a company was caught by surprise when they discovered that a new IC daughterboard they designed and mounted on the original IC pinout location suffered from radiated immunity issues. The product, which is an audio device, exhibited tone distortion when exposed to radiated emissions in the 1.2 – 1.4 GHz range. The original IC had been in service for over ten years and was no longer available. The new IC, based on ARM architecture and powered by 3.3V, was intended to replace it.

The daughterboard (covering an area of approximately 374 mm² and with a 5 mm distance to the main board) forms a capacitance of approximately 1 pF (calculated using the simple equation C=ε₀ε_RA/h). The long trace from the daughterboard to the main board likely has an inductance of about 10nH. The self-resonance of this board is then estimated to be 1.5GHz, indicating a higher likelihood of immunity issues in this frequency range.

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