The importance of studying EMI electromagnetic interference:
EMI is a common problem that needs to be addressed in products in various industries such as military, defense, communication systems, electrical and aerospace, home appliances and so on. So how to prevent EMI electromagnetic interference has become the hottest issue in the hardware development industry today.
Electromagnetic interference (EMI) is an EMC phenomenon that occurs when the operation of an electronic device is interfered with by an electromagnetic (EM) field, and usually occurs when the device is in close proximity to an EM field, which can disrupt the RF spectrum of the product itself. EMI can come from a variety of emitting sources, both natural and man-made, and it can take on a variety of characteristics depending on its source and the nature of whatever mechanism is emitting the interference.
There are various methods used to prevent and minimize interference in electronic devices as it affects the circuits and prevents them from working properly.
EUTTEST offers a wide range of EMC test equipment that is dedicated to keeping engineers on top of the competitive landscape when designing electronic equipment and developing new ways to prevent EMI damage to circuits.
In this article, we will discuss in depth the history of EMI and its causes, best practices for preventing or minimizing EMI, and the difference between EMI and EMC.
The history of EMI:
Electronic interference was officially recognized in 1933 when a subcommittee of the International Electrotechnical Commission (IEC) joined in Paris under the name CISPR (International Special Committee on Radio Interference). The subcommittee was formed to obtain more information on the possible long-term effects of RF technology.
With the popularity of the radio and its debut as a must-have household appliance during the Great Depression, the electronics community began to notice that intentional and unintentional radio frequency transmissions were beginning to affect electrical systems.
As a result, not only did EMI awareness begin to grow in the electronics community, but by 1934, CISPR began producing and distributing specific requirements.
According to EMI Solutions Inc . . these requirements include recommended allowable emission and immunity limits for electronic equipment that have evolved into most of the world's EMC regulations.
After the 1960s, researchers became increasingly concerned about electromagnetic interference.
For example, in 1967, the U.S. military issued "Mil-Standard 461 A," which establishes the ground rules for the testing and verification requirements for electronic equipment used in any military application, including emission and sensitivity limitations for any new electronic device. [Source]
In addition, in 1979, the Federal Communications Commission (FCC) imposed legal limits on electromagnetic radiation from all digital devices.
By the mid-1980s, EU member States chose to adopt several new methodological directives to meet the technical requirements of various products, so they did not end up creating barriers to trade.
An example of this is the EMC Directive 89/336/EC, Article 2, which states that it "applies to equipment which is susceptible to electromagnetic interference or whose performance is susceptible to such interference".
It is important to note that this is the first time that the requirements of the law on exemptions have been enforced, and the first time that specific emission devices intended to serve the public have been enforced.
As time goes on and electronic devices become smaller, faster, and more powerful, these regulations mentioned above continue to evolve. With these new systems, improvements mean they have a greater ability to interfere with the operation of other electrical systems.
Many countries now have similar requirements for products to meet some level of electromagnetic compatibility (EMC) regulations.
Causes of electromagnetic interference:
In all cases.EMIs all occur due to three factors: source, transmission path, and response (at least one response is unplanned).
EMI can occur in many different ways and from a variety of sources. Nonetheless, it stems from the presence of unwanted voltages or currents that can negatively affect the performance of an electronic system or electrical device.
Different types of EMI can be categorized in several ways:
1. EMI sources
One way to categorize the type of EMI is based on how it was generated (i.e., the source of the EMI), which can be naturally occurring or man-made.
Naturally Occurring Interference-This type of EMI can come from a variety of natural sources and phenomena, such as atmospheric types of noise like lightning or thunderstorms.
Human Interference-This type of EMI usually occurs due to the activity of other electronic devices in the vicinity of the device (also known as the receiver).
2. EMI bandwidth
Another way to categorize EMI is by bandwidth. Simply put, the bandwidth of EMI is the range of frequencies that experience EMI. This can be categorized into two types, broadband EMI and narrowband EMI.
Broadband EMI consists of EMI that does not occur at individual/discrete frequencies, which occupy a large portion of the magnetic spectrum.
In addition, they exist in different forms and may come from natural or anthropogenic sources.
Common causes of broadband EMI include arcing or corona discharges from power lines, and it makes up a large portion of the EMI problems in digital data devices.
Examples of such electromagnetic interference include faulty brushes in motors/generators, arcing in ignition systems, bad fluorescent lights, defective power lines and solar disruptions that interrupt communications satellite signals. Fortunately, these problems last only a few minutes.
In contrast, narrowband EMI consists of individual carrier sources (or narrow bands of interfering frequencies) that are generated by parasitic signals produced by different types of distortion in the transmitter, or in the form of oscillators [sources].
It is important to note that these types of spurious signals will appear at different points in the spectrum and may cause interference to other users of the radio spectrum.
3. EMI duration
Finally, EMI can be categorized into different types based on the duration of the interference (also known as the time it takes for the interference to occur). This typically categorizes EMI into two groups: continuous and pulsed EMI.
Continuous EMI, as the name suggests, is interference that is continuously emitted by a source. The source of the interference can be man-made or natural, but it's important to note that the interference is experienced continuously "as long as there is a coupling mechanism (conducted or radiated) between the EMI source and receiver," according to Circuit Summary.
Impulse noise is a type of EMI that, like continuous EMI, can be either naturally occurring or artificially created. That is, this type of interference occurs either over a short period of time or intermittently.
For example, lightning, switching systems, and similar sources can generate impulse noise that can disturb the voltage or current balance of nearby connected systems. [source]
Now that we've detailed the various types of interference you may encounter, it's critical to discuss the nature of electromagnetic interference.
EMI consists of electromagnetic waves that include E (electric) and H (magnetic) field components and oscillate at right angles. Take a look at the graphic below to better understand how the electric and magnetic fields of EMI interact.
How electric and magnetic fields interact in electromagnetic interference
These field components respond differently to parameters such as distance, voltage, current, and frequency, making it critical to understand the nature of EMI.
Why?
Due to technological advances in electronic components in recent years, electric fields are often the main component of interference. By knowing which field dominates, you can solve the problem more clearly and quickly. Then use different solutions to eliminate the effects of EMI electromagnetic interference.