Modern electronic design is a challenging task even when engineers can focus entirely on the basic objective of producing a cost-effective, fully functional circuit board. Clock frequencies are increasing, package sizes are decreasing, efficiency must be high, noise must be low, and mixed-signal architectures have become the norm. Designers are busy trying to reconcile competing demands while bringing products to market within tight test-and-development schedules. It’s no surprise that electromagnetic compatibility (EMC) is often given less engineering attention than it deserves.

Unfortunately, less engineering attention translates into more EMC failures, and EMC failures can cancel out much of a design team’s successes by creating delays, adding new costs, and necessitating redesigns. Achieving EMC compliance is a complex process involving a number of interrelated variables and practices. Nonetheless, understanding some of the basic failure modes can help you begin to implement a robust EMC plan. In this article, we’ll look at ten issues that make engineering companies less likely to pass EMC testing. The first five are general concerns that must be addressed at the technical, managerial, and cultural levels within an organization. The second five pertain more specifically to design engineers.

1. Inadequate Understanding of the Objective

Electromagnetic compliance is a minor or nonexistent component of undergraduate engineering programs. In many cases, engineering students will graduate without any formal study of EMC as a design task or as a product qualification process. This places a significant burden on young engineers who must attempt to gain proficiency in EMI and EMC while navigating the complexities and stresses of a new career.

This problem is less serious in companies that maintain a culture of knowledge-sharing and that help experienced engineers to effectively mentor junior engineers and review their work. But packed schedules and strapped budgets often make this sort of education and collaboration impractical, and where on-the-job training is encouraged and prioritized, knowledge transfer may still be inadequate because EMC proficiency is relatively uncommon even among senior engineers.

2. Neglecting EMC during Schematic Design and PCB Layout

A wide variety of design practices influence a device’s ability to comply with EMC requirements. Component selection, clock frequencies, spread-spectrum features, differential signaling, communication protocols, shielding, PCB plane layers, grounding techniques—these are under the designer’s control, and they all affect the extent to which an electronic system can operate successfully while resisting received EMI or generating acceptable levels of EMI.

EMC testing technicians receive many products that are in the final stages of the design cycle, or even the early stages of the production cycle, and yet have little or no prior evaluation of EMC performance. Failures occurring in these situations will require costly redesigns or suboptimal corrective measures. Whenever possible, designers should integrate EMC awareness and preparation into all stages of the development cycle.

3. Unsatisfactory Communication

The professional world is increasingly filled with devices, technologies, and software applications that are intended to make communication easier. This can sometimes distract us from the fact that meaningful, productive communication is still challenging and requires concerted, collaborative effort.

EMC failures can be prevented by enhancing two categories of communication: first, the sharing of expectations, lessons learned, and design strategies within an electronics company; and second, the movement of relevant experience and expertise from EMC professionals to engineering teams. Designers should consider the quality and quantity of communication and educational resources when looking for EMC consultants and test labs.

4. Test Preparation Is Lacking

Much EMC assessment can occur before a product ever goes to the EMC testing facility. A rigorous, iteratively updated EMC prep procedure, part of which should be a formal design review dedicated specifically to EMC, can help companies or engineering teams address issues that are likely to result in failure at the test lab.

5. Test Equipment Is Lacking

High-quality test and measurement equipment is a major investment for small companies, and even large, established engineering firms may struggle to maintain and update the arsenal of oscilloscopes, logic analyzers, signal generators, multimeters, power supplies, and so forth that their engineers depend upon.

Thus, no one wants to hear that the company must also find a way to pay for specialized EMC test equipment—examples of this include EMI signal generators, line impedance stabilization networks, lightning-surge simulators, and horn antennas. But the fact is that investing in carefully chosen EMC equipment, and thereby enabling some degree of in-house test capacity, can help to avoid the various costs associated with EMC failures. 

6. Digital Frequencies Are Too High

A perfectly sinusoidal signal emits energy only at the observed frequency of the signal. Rectangular waves, however, emit energy at the observed signal frequency and at multiples of the observed signal frequency, and for this reason they are more likely to produce problematic EMI. An easy way to reduce a device’s high-frequency emissions is to choose lower frequencies for digital signals.

The typical or default clock frequencies for microcontrollers, data converters, switching regulators, and other ICs may be much higher than what an application actually needs to meet performance requirements. It often makes sense to significantly reduce clock frequencies, especially if EMC compliance is a higher priority than processing power, data throughput, or output ripple.

7. Encouraging Wires to Act Like Antennas

Short PCB traces do not efficiently radiate or receive electromagnetic radiation at the frequencies used in most electronic devices. However, these same frequencies can produce significant emissions when a signal is sent through a relatively long wire, and this long wire will also be a better receiving antenna for ambient radiation.

It’s worthwhile to look for ways to avoid sending high-frequency signals through wires or cables, and if high-frequency transmission is necessary, shielded cables and differential signaling should be used.

8. Using a Switching Regulator When a Linear Regulator Would Suffice

Inductor-based switch-mode power supplies are very common and might now be considered the default method of generating a regulated supply voltage. Switching regulators are advantageous in situations that require long battery life or minimal heat generation, but designers should carefully weigh this enhanced efficiency against the switcher’s tendency to produce conducted and radiated emissions.

Switching regulators are not always as efficient as datasheets imply, and even when operating conditions do allow for high efficiency, the practical benefit to the application may not compensate for the increased risk of EMC problems. 

9. Inadequate Attention to Current Loops

The real-life business of drawing schematics and laying out PCBs can obscure the basic physical properties of electricity. It is easy, for example, to unconsciously imagine electrical current as something that originates in the schematic’s VDD symbol and ends in the schematic’s GND symbol.

When we design for EMC, however, we need to remember that current always flows in a physical loop: from the source, to the load, and back to the source through a return path. If this principle is not active in the designer’s mind during PCB layout, the board might end up with unnecessarily large current loops, and larger current loops are more susceptible to EMI problems.

10. Lack of Shielding

Shielding products—including EMC tape, EMC gaskets, board-level cages, and absorber sheets—are a legitimate aid to EMC compliance and should not be overlooked during the development process. Excellent circuit-design and PCB-layout practices cannot always prevent certain components or subcircuits from producing too much EMI or being highly susceptible to received EMI. In such cases, shielding may be a significant factor in EMC success, and if the need for shielding is recognized and investigated early in the design cycle, optimal products can be chosen and costly redesigns can be avoided.

About DENPAFLUX

DENPAFLUX (previously mitai) is committed to solving your EMC challenges in ways that are as straightforward and efficient as possible. Our team have personally experienced these EMC failures while working with our customers, and we are determined to provide expertise from experienced EMC professionals, powerful interactive EMC visualizer tools, and other EMC services that you need to build a reliable and EMI-free products without costly delays and redesigns.

Contact us today to discuss how DENPAFLUX’s unique blend of expert guidance and AI-driven analysis can turn your next product into an EMC success story.