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What is EMI Protection?

If radio signals and waves were tangible and visible, then it will be impossible to move between two ends of your apartment without tripping.

Now, what are those things that keep the signals from coming in contact or crossing? How is it possible to pick up your phone without this signal interfering with your laptop’s WiFi connection and cause some disruptions? This disruption is what we refer to as electromagnetic interference.

The truth is that we hardly see them due to an efficient electromagnetic interference protection or shielding, which is also called EMI protection. Before we go into details, we will explain what EMI means, what EMI protection means, and the types.

Please continue reading to comprehend all you should know regarding EMI protection as well as those materials that gives these signals a proper check.

What Does EMI Mean?

EMI Protection

EMI, described simply, involves the transmitting of undesirable electromagnetic radiation into an electronic or electrical device. The signals interfere with the operation of the device, which could cause great harm. Also, EMI can come up or originate from different sources, which could be both man-made and natural. EMI takes place anytime one source disturbs or disrupts the signal of another source.

Engineers also call it RFI, which means radio frequency interference. Although the above instance explains a negative result of the EMI, this form of interference could lead to more issues than make you mis your bars on some favorite songs.

In addition, EMI shouldn’t even emanate from a specific outside source. Also, internal EMI, where one of the components of the device generates interference in a different component, is known as a usual source of issues. Upstream issues having the conditioning and quality of different power sources are also well-known common culprits. Also, these internal EMI types working hand in hand can cause real issues for device builders and designers.

As if the sources haven’t caused enough issues, nature itself could also generate EMI. Some atmospheric phenomena such as solar systems and thunderstorms are all natural emitters of an electromagnetic radiation. Also, they could have some negative effects on the electrical devices.

What is EMI Protection?

With all the issues caused by EMI, EMI protection is very important. Our devices require some protection and safety from picking the wrong signals up, and security for choosing the appropriate and right signals. With EMI protection, you will be able to increase this success.

EMI protection involves a material that stops electromagnetic interference. This is made up of a specific metallic screen, which helps in absorbing any interference that has been transmitted via air. In addition, EMI protection exists to help protect your device’s electronics.

Furthermore, as these signals get to your device, this screen goes ahead to absorb them. This causes a current in its body. This current is then absorbed by a ground connection. This EMI shield helps in absorbing any transmitted signals even before they get to the device’s sensitive circuits. It also helps in ensuring the cleanliness of the protected signal.

One important example of why the EMI shield is very necessary is your Smartphone. You have different intricate, sensitive, electronics working at one to ensure that the display says exactly what it is saying. With an EMI shield, it helps in preventing random waves and signals form frying sensitive electronics. Devices like key fobs and Wi-Fi routers require the ability of transmitting the RF signals wirelessly.

Metal enclosures, as well as other enclosures blocking EMI could also block any transmission relied on by these devices. A wise and effective choice for all these applications is polycarbonate enclosures. Gaps or seams that are not well secured can compromise the performance of the enclosure shielding.

Even the small apertures present in any enclosure can serve as antennas, which allows the entering or leaving of EM radiation. To fight this, designers of enclosures will specify the enclosures with continual body designs.

Types of EMI

Narrow-band EMI

This usually happens to radios, TV stations, as well as mobile phones. This is because it happens over a specific discrete frequency. Anytime signals cross, devices malfunction. The customer can simply tune out that disruption, which won’t bring any damage to the equipment.  

Broadband EMI

This takes place over a broader spectrum because it occupies a massive part of the electromagnetic spectrum. Broadband EMI is a form of EMI which can cause maximum harm to devices. Also, you notice this form of interference at its peak while using a device featuring a specific digital data link.

Furthermore, something as easy as a motor’s worn brush can lead to EMI. Also, a fluorescent light having defects implies EMI. This similar interference could appear from a jet engine’s igniter. Defects present in a power line will lead to interference too.

Taking a look at each case mentioned above, the devices you are trying to utilize can have varying transmitted frequencies, blend them up, after which they are sent out over a very broad spectrum.

How is EMI Generated?


EMI or Electromagnetic interference is a disturbance that is created through the changes in voltages and currents that result due to three main sources.

Natural EMI

Some natural events happening in space or on earth could cause natural EMI. Humans have no hand in the creation of EMI. This occurs as a result of weather changes like rain, snowstorms, thunderstorms, etc. Also, some natural sources such as cosmic noise and solar radiation also create EMI. In addition, the natural EMI has an effect on older equipment and to a larger extent on RF communication. Notably, the modern equipment isn’t just affected a little by the natural EMI in contrast to the human made EMI.

Human-made EMI

All the electrical devices manufactured usually release EMI that are human-made. This interference is usually caused whenever two signals come near or whenever many signals meet themselves at just one frequency. All this helps in obstructing the devices’ operation whenever they have a contact with an EMI.

Also, this EMI is majorly seen in devices such as igniters, generators, power lines, radio transmitters, electric motors, phones, etc. Such devices and equipment are usually known to result in dangerous EMI levels.

Internal or Inherent EMI

For inherent EMI, this electromagnetic energy that is released from a device can cause its breakdown. That noise caused internally or inside is from the electron’s thermal agitation which is moving through its circuit resistor.

How to Reduce or Eliminate EMI


This is the most preferred way for containing coupling or radiation in victim or source devices. Usually, it is made up of encasing its circuit in a well sealed enclosure, like a metallic box. Furthermore, shielding is important because it helps in reflecting electromagnetic waves in the enclosure as well as absorbs waves which aren’t reflected.

For majority of cases, a very little radiation somehow penetrates the shield, if this shield isn’t very thick. Practically common metals will serve this shielding purpose (e.g. aluminum, steel, and copper).


This is a direct way of eliminating any undesirable signals, and for this case, passive filters function effectively, and they’re useful in majority of new equipment in minimizing EMI. Also, filtering usually begins with the AC line filter, which stops the entering of bad signals into the powered circuits or power supply. It also stops the addition of the internal signals to the AC line.

Furthermore, filtering is usually used with connectors and cables on the lines out of and into a circuit, and there are special connectors which have low-pass built-in filters where their major function is softening the digital waveforms to help in increasing the fall and rise tomes as well as reduce the harmonic generation, with respect to electronic design.


This has to do with establishing of electrically conductive paths in-between an electronic or electrical element of any system as well as a reference point, according to the DAU. Also, it could indicate electrical connections that are created to Earth.

Significance of EMI Protection

It is very crucial to understand the need for EMI protection for numerous reasons. As regards the development side of the spectrum, the product of a company is only as effective as it functions once it gets to the end user. For instance, if an electronic device malfunctions continuously, that is a bad indication for the company.

Developers are experiencing greater challenges as regards combating EML. This is because faster operating electronics makes it difficult to manage interference. However, the inability of engineers and designers to account for EMI will most likely result in a faulty product.

Furthermore, workers who often handle large amounts of big data could find it difficult to handle EMI  as interference can disrupt the mediums through which they gain access to such information. EMI is something that needs serious attention, both from the workplace environment side  and product development side.

EMI protection is very important irrespective of the product.  In as much as conductive silicones and gaskets are an ideal option in terms of product, another consideration may be the right type of window film to shield office locations from interference.

Also, EMI protection is crucial in shielding sensitive electronic designs from external signals and as well preventing the interference of stronger signals with nearby electronics. With a PCB design checklist, you can figure out what needs protection and how to achieve it.

Electromagnetic interference impacts sensitive electronics and has an impact in different sectors, including industrial electronics, and mission-critical military electronics. Therefore, it is important to ensure that the electronic systems get enough protection against EMI.

Common Tools and Techniques in EMI Protection

emi emc shielding materials

EMI protection simply involves the integration of different countermeasures to shield electronic and electrical devices from EMI. There are methods of EMI protection, this includes:

  • The majority of electrical device designers will build an enclosure box made from material like steel or aluminum. These metals feature natural EMI shielding. Also, a well constructed metal enclosure can retain and redirect the interruption instead of allowing it to get to the device inside. Silver, copper, aluminum, and other kinds of steel are materials widely integrated due to their natural resistance to EMI.
  • Installing an electronic enclosure having an EMI-shielded gasket reduce or prevent EMI in a device. Also, these gaskets comprise standard materials such as neoprene. However, they comprise conductive metallic linings such as wire mesh that transform the gasket into a conductive barrier that fights EMI.
  • Another great alternative for including EMI resistance in an enclosure is the use of conductive spray coatings. Also, these coatings feature metals such as nickel or copper in a spray-on format. Therefore, one could apply it to non-conductive materials and as such, offering a great way to include EMI resistance to various types of device enclosure.
  • EMI-shielded cables can combat various EMI-transferring properties features by electrical cables. Furthermore, cables can generate and receive EMI. Shielded cables can as well minimize vulnerability to both. Therefore, this makes them an effective and crucial part of the solutions toolbox that helps to enhance the EMI resistance of a device.
  • The majority of device designers usually include electronic filter circuits to the most crucial components of a device to minimize their susceptibility to EMI. There are several filter designs available. Filters are a popular and versatile choice for regulating EMI in different devices. This is because you can calibrate them to accept particular frequencies and reject others.

Guidelines for Regulating EMI

When governmental bodies realized the importance of EMI, they enforced equipment compatibility via regulations. For example, IEC 61000-4, standardizes test methods. The relevant sections to this discussion are IEC 61000-4-5 for high-energy transients (SURGE), IEC 61000-4-4 for fast transients (FTB), and IEC 61000-4-2 for electrostatic discharge (ESD). These are test methods that depend on only realistic models for electrical noise.

Before the application of protective elements, you need to consider these rules:

  • Consider EMI protection while designing the circuit, not after designing the circuit.
  • Ensure you block interruptions that are near to the source, do this before they reach the equipment; you can redirect them to ground.
  • Locate all sections that can expose to EMI disturbance from sensitive circuitry.

Since signal circuitry can’t resist kilovolt-level voltages, you need to exclude these disturbances from the input, convert to current, and heat them. Isolation is of great importance for the occurrence of high ground-loop currents and longer lines in industrial systems.

Also, an ESD current pulse with 30A peak may only generate tens of millivolts of resistive voltage drop. Skin effect is important at these high frequencies as it helps to dramatically increase wire resistance by ensuring current flows within microns of the conductor surface. You need a large surface area for ground connections to counteract this effect. This helps in maintaining low resistance.

Common EMI Protection Components

Gas arrestor

A Gas arrestor is a type of dish-shaped capacitor that contains gas, most especially neon. If there is an voltage in excess of ~100V, this will create a plasma that reduces the voltage at low levels. Also, gas arrestors retain high-level transients.  However, they are not ideal for fast transients since the emergence of plasma is time-consuming. They are also not ideal for mains protection. Gas arrestors are very difficult to utilize with low-source impedances.


Varistor is an arrestor that comprises metal oxide (mostly zinc). This component looks like a tablet having two connectors, one on each side. It has similar characteristics with a zener diode. Therefore, it reacts much faster than the gas arrestor. However, it possesses high leakage currents particularly when the signal reaches the clamping voltage.


Capacitors are the most crucial protective component. The important properties of capacitors include voltage capability, inductance, equivalent series resistance (ESR), and high-current capability. Placing the capacitors in the right location in the layout helps to reduce EMI. When capacitors are properly used, they usually create a high-frequency ground to create a lowpass filter.

Series resistors

Series resistors are important and low cost protective components. These EMI protection components can replace more expensive components if properly selected based on power dissipation and resistance.

EMI Protection Materials

There are different materials for EMI protection. These materials should feature some particular electrical and magnetic properties. Also, they should retain or discharge the radiation generated by communication equipment and electronic devices. Also, the absorption shield type is more effective as it becomes safe for the environment. Most times, non-intrusive materials are used for EMI protection.

Pre-Tin Plated Steel

This material usually less expensive than the other type of metals integrated in EMI protection. However, it is a perfect option for lower frequencies, particularly in the kHz range. In particular, carbon steel, offers low-frequency shielding characteristics that other metal options don’t offer. Also, it shields the steel from any form of corrosion.

Copper Alloy 770 / Nickel Silver

This is also commonly referred to as alloy 770. Copper alloy 770 comprises nickel, Zinc, and copper. It is often used due to its resistance to corrosion. Furthermore, copper alloy 770 is a perfect option for EMI shield used for mid kHz range up into GHz. Copper alloy features a permeability of 1. This shows that it is ideal with MRI machinery.


Copper is a totally different material. It is the most reliable metal used for EMI protection because it reduces both electrical and magnetic waves. Also, copper is widely available. You can find it anywhere EMI protection is necessary from hospital equipment to basic consumer appliances.

Copper is more expensive than pre-tin plated steel or copper alloy 770. However, it has a greater rate of conductivity. This makes it a very effective option for an EMI shield.


Due to high conductivity and its strength-to-weight ratio, this material can function well as an EMI protection material. Aluminum has almost 60% of conductivity.

Application Areas of EMI Protection


The increasing use and demand for electronic devices and mobile wireless communications has made manufacturers to seek for ways to shield their products from interruption.


The automotive industry as a whole is experiencing a new wave of autonomous cars and electric vehicles across the globe. Also, these vehicles come with sophisticated features such as hands-free systems, touchscreen systems , onboard GPS navigation systems, and Bluetooth. The electronics present in these vehicles resulted in some challenges when combating EMI. Therefore, there is a higher demand for EMI shielding in autonomous and electronic vehicles.


The telecommunications industry is another industry experience rapid growth globally with the rising adoption of smartphones and the introduction of new and sophisticated technologies such as 5G. Also, the towers and components utilized require effective protection to enable smooth transfer of data. Furthermore, there is high requirement for EMI shielding in the telecommunication sector. This requirement will increase even further in the future.


 The defence industry needs a high level of EMI protection in its operation. EMI shielding is now one of the relevant technologies in the military sector. It offers protection to trucks, drones, control panels, and helicopters. This helps to safeguard sensitive components. Also, the quality of EMI shielding is very important in fighting against strong disruptions.


It has become crucial to minimize the vulnerability of aerospace equipment to EMI. When aerospace equipment experiences electromagnetic interference, it must not generate radiation that impedes operations. As a result, the integration of EMI filtering materials has rapidly increased in the aerospace industry. Also, the increasing number of space exploration missions is a reason.


By now, you should understand what EMI protection is all about. We don’t live in a perfect world. Therefore, our electronic and electrical devices can become susceptible to negative impact by EMI. We know have a clear understanding of how EMI affects electronic and electrical devices. Also, we now know the measures to adopt to help prevent or reduce EMI.  We have, therefore, created guidelines to help us control acceptable limits of EMI. Furthermore, modern technology has offered various options made from various materials to prevent unwanted interference.