Electromagnetic compatibility (EMC) testing ensures that electronic devices can function safely without causing or experiencing interference. When a product fails this test, it can be a good opportunity to re-examine and improve the design.
Common reasons products fail EMC testing
The global EMC testing industry is expected to hit $4.48 billion in 2031 as more industries and regions require EMC tests for critical applications. However, even some sophisticated designs can stumble during the EMC testing phase. Here are some of the most common reasons for these failures.
PCB design
Printed circuit boards (PCBs) are the canvas upon which various electronic components, like semiconductors and capacitors, communicate. Poor PCB layout and layer stack-up can cause EMC issues. Some design recommendations or rules of thumb may come from outdated sources that fail current EMC compliance standards. If the electronic pathways are not laid out properly, the board can emit excess noise.
Cable shield termination
Cables connected to devices can act as antennas and emit excess noise. If these cables lack proper treatment, they could penetrate shielded enclosures and cause radiated emissions. Custom functional coatings can help with heat resistance, flexibility and other factors affecting emissions.
Power distribution design
Designing a power distribution network (PDN) requires a low-impedance transmission line to quickly and effectively transfer energy from the power source to the switching IC. During this switch, there is a period when both output devices are simultaneously on, causing a large current pulse.
Gaps in return path
Gaps in the return path commonly cause products with excess radiated emissions. If the return current doesn’t have a clean path, it will find one. Sometimes, these currents will create routes that increase emissions.
Shielding design
Even a small gap in a shield or enclosure can leak radiation. Apertures or slots should have the correct dimensions to maintain the shield’s integrity and effectiveness.
How to fix EMC test failures
If a product fails EMC testing, there are ways to troubleshoot and resolve the issue before resorting to trial and error.
If your product fails emissions testing
Emissions testing failures mean the product is producing too much noise. The goal is to reduce or block noise at the source before it radiates.
Assess cable orientation: reroute cables – change their orientation or try an S-bend – to see if it reduces emissions
Compare polarisation: if emissions differ between horizontal and vertical orientations, it can help technicians locate the source. Emissions problems usually show up in one orientation more than the other
Check frequencies: it can help to check if the frequencies on the EMI receiver match the product’s clock and crystal frequencies.
Use ferrite clamps: ferrite clamps can help correct cabling issues or identify the problem’s source. However, they are a temporary solution
Adjust programmable options: sometimes, emissions come from software-controlled circuitry. Consider this approach to identify or resolve potential problem components
If your product fails immunity testing
Immunity failures mean the product is too sensitive to external interference. The focus should be on identifying and strengthening the product’s weak points.
Double-check the setup: even small changes can significantly influence test results, so ensure the test has reliable power and all cables have secure connections
Assess functionality: verify that the device works normally before the test exposes it to interference
Look at coupling mechanisms: the coupling mechanism itself may be the factor causing the product to fail. Teams can renegotiate the coupling mechanism under some conditions
Retest the product: a retest may reveal how much the team has to modify the design to pass the test
Why EMC testing matters
EMC testing ensures that electronic devices are safe, reliable and compliant with industry standards. Here are several reasons why good design through proper testing impacts the product and its users:
Safety in critical systems: in critical industries like automotive, medical, and aerospace applications, EMC failures can cause serious malfunctions. Reliable electromagnetic activity ensures safety and stability in these systems
EM spectrum preservation: the world has a finite electromagnetic spectrum shared by electronic devices. Meeting EMC standards helps maintain signal integrity for communication, navigation, and other systems
Product performance and reliability: products that meet EMC standards are generally more reliable in the field, contributing to long-term performance and fewer customer issues
Regulatory compliance: EMC compliance is mandatory in industries like healthcare and many geographical regions. Failing tests can delay certification and harm brand credibility
Building stronger EMC designs
Failing an EMC test is an opportunity to strengthen the product’s design. With careful analysis and intentional improvements, teams can correct most issues without a complete redesign. Designing the product with EMC in mind ensures better performance and safety in the field.
About the author:
Ellie Gabel, Associate Editor, Revolutionized
