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What is EMI and EMC in PCB?

Posted:12:00 PM April 06, 2023 writer: ​NextPCB

Definition of EMI and EMC

Electromagnetic interference or EMI originates from electromagnetic radiation and refers to any form of background noise or disturbance that possibly traces back to it. Electronic devices and machinery may experience performance degradation or improper functioning as a result of this interference. Radio waves, other electronics' radiated EM fields, power supply oscillations, and mechanical systems' radiated EM fields are all potential causes of EMI.

In contrast, EMC (Electromagnetic Compatibility) describes how well electronic devices and equipment function when exposed to electromagnetic interference. Performing electromagnetic compatibility (EMC) testing is necessary. To prevent electromagnetic interference (EMI) from disrupting the operation of any electronic device or piece of equipment.

EMI in daily life

PCB designers frequently use EMI and EMC together in the layout process. Making a circuit that is both EMI-proof and compatible with other electronics in use nearby is a top priority for designers. The device's ability to resist electromagnetic interference (EMI) from other sources and operate successfully depends on the quality of the executed EMC design.

Designing for electromagnetic interference and electromagnetic compatibility involves a few considerations, like the nature of the transmitted signals, the circuit's layout, and the materials. Careful grounding, shielding, and filtering procedures can lessen EMI's effect on the PCB, while strategically placed components can boost EMC.

In this article,

Possible Sources for EMI

Sources that cause EMI

There are many potential environmental causes of EMI (Electromagnetic Interference). They may come from places like:

  • The generation of high-frequency noise by digital signals, such as those produced by microprocessors and digital circuits, can cause complications when other devices expose to it.
  • Analog signals, such as those generated by amplifiers and sensors, can potentially cause interference due to their intrinsic noise.
  • One source of electromagnetic noise that might disrupt other circuits is the power supply. The power supply's electromagnetic radiation or ripple in the output can both contribute to this problem.
  • The electromagnetic radiation emitted by other electronic devices in the vicinity can cause disruptions to the functioning of other equipment. For instance, cell phones emit radiation that might disrupt other electronic devices in the area.
  • Machines, such as motors, can produce electromagnetic fields that might disrupt nearby electronics.
  • Lightning strikes generate high-frequency electromagnetic radiation, which can interfere with electronic circuits.
  • Interference from radio and television transmissions, mobile phones, and other radio sources can disrupt electronic circuits.
  • Environmental factors such as humidity, temperature, and altitude can all affect electrical circuit performance and contribute to electromagnetic interference.

PCB designers need to think about the various possible ambient sources of electromagnetic interference (EMI) when making electrical gadgets. Using the appropriate shielding, filtering, and grounding techniques can protect the dependable operation of electronic circuits against EMI.

Types of EMI

Types of EMI

Electromagnetic Interference can impair the performance and functionality of a PCB in several ways. Conducted and radiated EMI are the two most common types of electromagnetic interference.

Conducted EMI

The term "conducted EMI" refers to electromagnetic interference that travels along the conductors of a PCB. The power supply can also cause conducted EMI by introducing noise and ripple onto the power rails of a PCB. PCB designers can mitigate conducted EMI through filters, ferrite beads, and suitable grounding techniques.

Radiated EMI

In contrast, radiated EMI is the form of EMI that travels over space as electromagnetic waves.  Radiated electromagnetic interference can be a severe worry for PCB designers, as it can interact with surrounding equipment and systems. To prevent radiated EMI, PCB designers can utilize shielding, grounding, and careful PCB layout design.

Magnetic Coupling

Magnetic coupling is another type of EMI that happens. Happen when the magnetic field produced by one circuit causes a voltage in a nearby circuit. Magnetic coupling can be problematic for analog low-level circuits that are sensitive to slight voltage fluctuations. PCB designers can utilize shielding, spacing, and twisted pair wire to reduce magnetic coupling.

There are various types of electromagnetic interference that can affect the performance and operation of a PCB. Radiated EMI propagates through space as electromagnetic waves, while magnetic coupling occurs when the magnetic field generated by one circuit induces a voltage in a nearby circuit. To achieve EMC compliance with their designs, PCB designers must account for different types of EMI and employ the proper mitigation strategies.

Mitigation of EMI

EMI can have a substantial effect on the performance and dependability of a PCB. Therefore, it is essential to employ the proper mitigation measures to limit the impacts of EMI on the PCB. Here are four common EMI mitigation techniques:

  • Shielding is the process of surrounding sensitive components with a conductive material. In order to prevent electromagnetic radiation from entering or exiting the enclosure. Using metal enclosures, conductive coatings, or metalized fabrics can provide shielding. To successfully shield against EMI, the shielding must be electrically connected to the ground.Shielding
  • By connecting the PCB to the earth ground in a low-impedance way, we achieve grounding. The EMI generated by the PCB can be mitigated and channeled away from the board with proper grounding. While completing grounding, be sure to use a dedicated ground plane, grounding wires, and grounding pads.


  • Filtering: Filtering is the process of removing undesirable frequencies from PCB-passing signals. EMI filters are typically composed of capacitors and inductors. They are designed to allow desirable frequencies through while blocking unwanted ones. Filters may be applied to both input and output signals to decrease EMI emitted or received by the PCB.

Filter Mitigation the EMI

  • Careful PCB layout design is essential for limiting electromagnetic interference (EMI). PCB designers can limit the amount of electromagnetic interference created or received by the PCB by employing strategies such as optimal component arrangement, decreasing the length of signal traces, and differential signaling. The PCB architecture should also incorporate a dedicated ground plane and sufficient shielding to limit the impacts of electromagnetic interference further.

EMI can have a substantial effect on a PCB's performance and dependability. Employing proper mitigation techniques such as shielding, grounding, filtering, and careful PCB layout design can help to decrease the impacts of EMI and ensure that the PCB is EMC compliant.

EMC Testing Standards

Making sure electrical devices can function without causing or being damaged by electromagnetic interference (EMI) is important in PCB design. The EMC testing standards that PCB designers must be familiar with vary from one market to the next.

The United States Federal Communications Commission (FCC) provides one of the most extensively used benchmarks for EMC testing. The Federal Communications Commission (FCC) establishes guidelines for acceptable levels of radiated and conducted emissions from electronic devices and mandates that all such devices be tested and certified for compliance. As wireless devices, like cell phones and Wi-Fi routers, might interfere with others operating in the same frequency range, this is especially crucial for them.

The CE marking established by the European Union is another significant standard. Products marketed in the European Union (EU) must bear the CE label, which certifies that they meet EU health, safety, and environmental regulations. Electromagnetic compatibility (EMC) testing is part of the CE certification process, and the standard specifies the allowable ranges for emissions (radiated and conducted) and susceptibility (to electromagnetic fields).

VCCI in Japan, ICES in Canada, and CISPR in Europe are a few examples of countries that have their own EMC testing standards. Radiated and conducted emissions, as well as tolerance to electromagnetic fields, are common areas of overlap between these standards.

Emissions and immunity testing are common components of EMC analysis. Testing for emissions ensures that the device does not produce excessive electromagnetic radiation that could disrupt other electronics while testing for immunity verifies that the gadget continues to function normally even when subjected to external electromagnetic fields.

EMI Simulating Tools

EMI simulating software

Tools for electromagnetic interference simulation play a crucial role in designing and developing printed circuit boards. These programs aid in the analysis and forecasting of EMI problems that a PCB may encounter, allowing designers to better prepare for them.

A variety of electromagnetic interference simulation tools, such as SPICE (Simulation Program with Integrated Circuit Emphasis), are at your disposal. SPICE is widely used to describe the electrical properties of PCBs and simulate the behavior of electronic circuits. On the other hand, PCB components and their interactions with electromagnetic fields can be modeled with electromagnetic simulation software.

The ability to spot EMI problems early on in the design process is a major advantage of EMI simulation tools. This can cut down on the price tag and time spent on building and testing physical prototypes. Instead of building physical prototypes first, designers might utilize simulation tools to test and iterate on potential designs.

PCB layouts can be optimized for EMI performance with the aid of simulation tools, which can be used by designers. You can use them to simulate how various component positions, trace routing alternatives, and grounding methods will affect EMI performance. This helps designers find the optimal arrangement for their project and prevent EMI problems.

PCB design and development are incomplete without EMI simulation tools. They help designers spot and correct EMI problems early on, optimize their layouts for optimum EMI performance, and guarantee that their PCBs are in compliance with all applicable EMC (Electromagnetic Compatibility) regulations.

Design PCB to Overcome EMI

Making sure electronic equipment doesn't generate or isn't affected by electromagnetic interference (EMI) is dependent on careful PCB design for EMC. While designing for electromagnetic compatibility, PCB designers should bear the following in mind:

  • Good EMC performance relies on a number of factors, one of the most important being the careful selection of components. Designers should pay close attention to the noise characteristics of the power supply and other crucial components when making component selections based on EMC characteristics.
  • EMC design relies heavily on the PCB layout, thus it's important to get it right. To reduce the possibility of EMI, significant thought must be given to trace routing, component arrangement, and grounding. Noise coupling between sections of the PCB can be reduced by properly routing high-speed signals and designing the grounding scheme.
  • Because of their prevalence as a potential source of EMI, power supplies demand careful consideration at every stage of the design process.
  • Filters, shielding, and low-noise power supplies can all help reduce electromagnetic interference.
  • A shield can lessen the impact of EMI.
  • A PCB can have some or all of its components insulated from electromagnetic radiation.
  • Filtering is another helpful method for minimizing EMI interference. Power supply and signal lines can have noise reduced and prevented from linking to other portions of the PCB by using filters.
  • Finally, testing and verifying the EMC performance of the PCB is crucial. Before going on to the actual prototype stage, it is common practice to use EMC testing equipment to ensure compliance with regulatory standards and simulation tools to identify potential EMI concerns.

PCB designers must pay great attention to component selection, PCB layout, power supply design, shielding, filtering, and testing to ensure their boards comply with electromagnetic compatibility (EMC) standards.


In conclusion, RF interference and electromagnetic compatibility are fundamental principles for any PCB designer to grasp. Electromagnetic interference (EMI) is a major contributor to the malfunction, noise, and decreased performance of electronic devices. Yet, EMC ensures that all electrical components may work together in harmony regardless of the presence or absence of electromagnetic fields.

PCB layout, component choice, grounding, and shielding are all factors that must be taken into account while designing for electromagnetic compatibility. Filtering, shielding, and grounding are just some of the methods that might help designers reduce EMI. To further guarantee that their PCBs are in accordance with all applicable regulations, designers must follow many EMC testing standards.

The significance of EMC and EMI mitigation will increase in the next years as the technology in use increases. To ensure their devices conform to rigorous standards and function as intended, PCB designers must stay abreast of evolving EMC legislation and industry best practices.

Ultimately, the success of electronic products and gadgets depends on a thorough comprehension of EMI and EMC. It is possible for designers to make EMC-compliant and dependably functioning PCBs by adhering to best practices, making use of simulation tools, and doing extensive testing.

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