How to Reduce Electromagnetic Interference: Best Practices

Now that we understand what electromagnetic interference is, how do you reduce its effects on electronic systems? Reducing electromagnetic interference (EMI) involves implementing various techniques to minimize its impact on electronic devices and systems. These include shielding, filtering, and grounding.

1.EMI Shielding

The primary (and most common) method used for reducing electromagnetic interference is the use of shielding. This is a protective barrier that blocks out signals from external sources. EMI shielding techniques can vary depending on the nature of the device and its intended use. Examples are:

• EMI shielded cables: shielded cables have a conductive layer, typically tape or braided wire. This EMI wire shielding sleeve acts as a barrier to reduce the effect of EMI on the signal being transmitted through the cable.
• EMI coatings: these are conductive coatings, such as conductive paint or metallic films that are applied to non-metallic surfaces with aim to create an EMI shield. These are usually plastic enclosures that may not prevent EMI themselves.
• EMI shielding gaskets: this refers to the conductive gaskets used to form an EMI shield between two surfaces, such as the seams or joints of a shielded enclosure. They are typically metal-embedded silicone gaskets that both seal and mitigate EMI.
• EMI shielding mesh: an EMI shielding mesh or wire screen is made of conductive materials can be used as a lightweight and cost-effective EMI shielding solution.

Electromagnetic interference shielding also involves large-scale objects such as walls or cages to contain or reduce its effects. EMI enclosures of this scale are necessary when EM radiation must be contained in a large area, or when it’s too difficult to shield individual components.

2. EMI Filtering

Filtering is another effective way to reduce electromagnetic interference. It primarily involves blocking conducted noise, which is the kind of EMI that travels along power cables or signal lines. Here is what you need to know about EMI filtering.

• The filter is often installed on the input of the device. Here, it blocks out any signals that deem unfit, and only allow the required signals through.
• After filtering, the EMI noise gets dissipated to the ground. In some cases, the EMI filter sends it back to the power source.
• Because most EMI issues are caused by high frequency noise, most filters you’ll find on the market are designed to block out high frequencies, and commonly called low-pass filters.
• EMI filters can be active or passive. A passive EMI filter actively uses power to reduce EMI, while a passive EMI filter makes use of passive components such as capacitors, resistors, and inductors.

It’s also good to know that, since electromagnetic interference filters only reduce conducted noise, it’s common practice to use them in combination with other techniques, such as shielding and grounding. This will ensure that you get maximum EMI protection, especially when dealing with sensitive electronic systems and devices.

3. Grounding for the Control of EMI

When it comes to reducing electromagnetic interference, grounding is an important concept to understand. In a nutshell, it involves connecting electronic components and circuits to a ground reference point.
This serves to provide low-impedance path for return current, a potentially helps to reduce EMI and its impact. In light of that, these rules apply when using grounding as a way to reduce EMI.

• Using grounding for the control of EMI will be successful only when the ground reference point is connected to a low-impedance path.
• For better results, ensure analog and digital components are separately grounded. This will prevent digital noise from coupling into the sensitive analog circuitry.
• Keep grounding paths short: Shorter grounding paths help minimize inductance and impedance and help with ensuring better EMI shielding results.
• Single point grounds suit low frequency interference such as audio waves. For higher radio frequencies, multipoint are more effective.
• On large planes, it’s necessary to create multiple grounding points.

Note that grounding for EMI reduction is different from grounding for safety purposes. Therefore, anyone intending to mitigate electromagnetic interference using grounding techniques must understand its basic principles, rules, and anything that’s required to ensure proper procedures.