What Is RF Interference?

What Is RF Interference?

Published: 28th February 2020

It all has to do with electronic devices interfering with each other within the crowded landscape of frequencies they operate in. And since we’ve progressed a great deal since the early days of radio, the term EMI, or electromagnetic interference, is now often used synonymously with RFI — but for the sake of being more inclusive.

What is RFI and EMI?

Since all electronic devices radiate a certain amount of electromagnetic radiation — also referred to as noise — their operation can be degraded when they either transmit or pick up unintentional electronic interference. That’s why you hear that telltale buzz when your car radio confuses an incoming cell phone signal with the radio station you’re listening to at the time. Moreover, not all EMI is man-made — natural occurrences, like lightning and solar flares, can also wreak havoc on electronic devices.

Of course, a slight buzzing sound may only be a minor inconvenience when you're listening to the radio or watching television. However, RFI can cause significant issues in an instance where a control system picks up the wrong signal, causing production delays and a subsequent loss in profits.

What Are the Causes of RF Interference?

Even when we limit our consideration of possible RFI causes to consumer electronics, the landscape is increasingly overcrowded. From cell phones to microwaves, our love affair with electronics means the potential causes of RFI grow by the day.

That’s why, for companies producing products that rely on electronic circuitry, RFI is a critical factor in every stage of product development, from design to pre-compliance testing. And as a result, determining whether or not a product complies with electromagnetic compatibility (EMC) requirements is crucial.

Due to the issues RFI can cause, it’s important to prevent it. Moreover, the Federal Communications Commission (FCC) regulates the emission standards for EMC, which Title 47 of the Code of Federal Regulations (CFR), or 47CFR, discusses. Non-compliance with 47CFR can result in fines, which is why it's critical to conduct pre-compliance testing to determine whether or not a given product complies with regulatory requirements.

Some potential causes of RFI include:

  • A concentration of electronic devices in a spectrum
  • A comprised connection of electronic devices
  • A poor enclosure design with low absorption loss

In many cases, a design flaw is the reason for RFI.

How to Minimise RF Interference

Several techniques can help in reducing or eliminating radiated emissions, including:

  • Shielding: An almost standard method for emission suppression is RF shielding, which should be incorporated into product designs as early as possible. The purpose of an RF shield is to protect vital circuit board sections or prevent emissions. Many types of guards are available for use, featuring different materials, shapes and thicknesses to improve permeability and conductivity. Examples include a metal film, conductive foam or metal box.
  • Filtering: Another option for eliminating radiated emissions is the use of filters, which can include three-pole filters that target the 150 kHz to 30 MHz range. A filter protects your product from emitted RFI from other electronic devices. Plus, it prevents its emitted RFI from interfering with other devices. Filters are available at both the consumer and commercial level, providing you with the opportunity to incorporate a filter into your product's design before it goes to market.

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