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RF Shielding with Environmental Chambers

An AES employee configuring a test chamber.

It’s difficult to picture life without the many devices that power our existence: cell phones, radios, smart televisions, wireless headphones, tablets, laptops, and pretty much everything associated with the so-called Internet of Things (IoT).

We take for granted, however, how all these instruments operate without affecting the others. The explanation is that their signals are regulated to avoid interference. Companies that produce these products conduct testing to ensure they emit signal strengths only in their allocated space.

That’s only possible with radio frequency shielding.

Radio frequency (RF) shielding is a form of electromagnetic shielding that blocks out radio frequencies. Certain test chambers are constructed with RF shielding, protecting devices under test (DUTs), usually related to electronics or computers, from radio frequency interference and enabling users to run accurate tests.

Here’s what you need to know about how RF is employed in environmental chambers.

Electromagnetic Radiation and RF Shielding

Electric and magnetic energy moves through space and time at lightning speed. Electrical pulses typically create this electromagnet radiation, also known as radio frequency waves, in the antennae of routine electronic and wireless devices, among others.

These radio waves are measured in hertz (Hz), with different devices relying on varied frequencies to function properly. Radio waves are part of an electromagnetic spectrum ranging from 3 kilohertz (kHz) to 300 gigahertz (GHz). For instance, microwaves rely on a specific type of radio wave range, including 1 to 30 GHz.

Most importantly, radio waves are used for telecommunication, such as medical devices, cellular phones, satellites, and other wireless electronics. While there isn’t clear evidence that exposure to electromagnetic waves is harmful to humans, the Federal Communications Commission (FCC) still provides regulations to ensure various entities abide by guidelines in their decision-making processes, accounting for the environmental impact of radio waves, including human exposure.

Electromagnetic interference can be incredibly detrimental to environmental testing, particularly for electronic devices that produce radio waves. It can affect the performance of these devices and the accuracy of the test results.

This is why labs employ radio frequency shielding, typically using Faraday cages to ensure electromagnetic radiation doesn’t enter or exit test chamber workspaces.

This ensures environmental testing is reliable, safe, and valid.

Why Is RF Shielding So Important in Testing?

For two main reasons, RF shielding is imperative for companies testing electronics, computers, medical devices, and anything with Bluetooth capabilities.

First, there are radio signals everywhere.

Just think of your neighborhood or apartment complex. It’s likely that when you open Wi-Fi on your phone, several networks (with signals ranging from weak to strong) pop up as options. Or consider leaving your favorite local radio station on during a road trip. As you get further from the city, you’ll lose the signal and, most likely, pick up another channel.

Such instances are minor nuisances, if nuisances, at all. But they illustrate the challenge engineers are up against: Radio frequency signals are everywhere at all times, including in labs.

These radio frequencies can interfere with testing to the point that they can affect the performance and functionality of DUTs. The only way to guarantee unambiguous results is to block outside signals and keep the device’s signals inside the chamber.

The second and more important reason why you need RF shielding is compliance.

The United States government, in the form of the Federal Communications Commission (FCC), strictly enforces safety restrictions on radio frequencies. The regulations cover everything from broadcast television and radio to satellite communications and aeronautical navigation.

Without limits, the power of the signals would cause massive interference, which poses threats to communication systems, proper operation of medical equipment, emergency response teams, and security as a whole. This is why personal-use walkie-talkies are highly regulated in terms of design, performance, and modifications. ‘Ham radio’ users, amateur radio operators, must be licensed by the FCC to transmit with power levels of up to 1500 watts.

Therefore, you’re only allocated a designated frequency range for your devices, and you’ll need to prove that your devices emit a signal that falls within the appropriate range. Test chambers with RF shielding isolate the DUT and prevent outside signals from interfering with the results.

It’s a crucial element of your testing that validates the resources and time you put into developing devices.

How Test Chambers Are Designed with RF Shielding In Place

Keep in mind that not all test chambers shield radio frequencies. If you don't have an RF chamber, you have to place your chamber into a Faraday cage to block radio frequencies. Resembling a metal shoebox, Faraday cages are made of conductive materials that keep out disruptive radio frequencies. Notably, Faraday cages also have to be conditioned prior to testing, which lengthens the testing process.

Furthermore, these testing conditions make it difficult for engineers to monitor DUTs.

Fortunately, a few innovative companies are constructing their internal workspaces to replace the Faraday cage, offering more workspace and speeding up testing without the additional conditioning step. Innovative designs of these test chambers provide blocking and trapping of a wide range of radio waves.

Every aspect of the chamber is considered.

For instance, Associated Environmental Systems’s (AES) FDR test chambers come with built-in features that trap and block a wide variety of radio frequencies (no Faraday cage required). These chambers rely on high-grade steel, specialized door gaskets, and other mesh enclosures that protect ports and air circulation paths.

These RF-shielding test chambers include:

  • Cellular, metallic, chromatic gaskets and conductive adhesives that seal the workspace
  • A honeycombed RF shielded grill that keeps the circulation motor cool
  • Electrical wiring fed through special RF filters
  • Standard and customer-requested RF-rated connectors, installed on a side-mounted interface plate to provide a shielded pass-through grid so you can communicate with the DUT

The level of attenuation (the strength of the signal the test chamber blocks and, by extension, isolates) also varies. Each test chamber is certified by an independent facility before being shipped.

Uses of RF Shielding in Environmental Testing

Companies use RF-blocking test chambers, such as AES’s FDR series, to test products in vitally important ways. For example, they block RF waves from penetrating chambers and contain RF waves within the workspace while engineers measure DUTs at the required temperature.

For research, users can measure phantom waves and the disruptive relationship between the human body and other objects on microwaves moving between wireless phones and cell towers. As you can imagine, it’s a very common occurrence.

These chambers also protect employees who work closely with RF products by preventing RF waves from escaping the chamber.

These capabilities are central to advancing new technologies. The innovations are numberless, but here are just a few developments made possible due to RF shielding:

  • Medical devices such as X-ray machines, MRIs, and heart monitors are built with electromagnetics to exchange vital health information.
  • Smartphones and other cellular devices depend on RF.
  • Desktop and laptop computers rely on electromagnetic radiation.
  • Handheld Bluetooth devices utilize ultra-high-frequency radio waves.
  • Electric motors and generators depend on electromagnetic waves to create power.

The possibilities with radio frequencies are staggering.

RF shielding helps us to solve some important problems facing humanity. We can expedite that research and development even faster with the benefits of test chambers with built-in RF shielding.

And that’s an encouraging thought.

Ultimately, RF shielding enables you to focus on innovation and performance to continue developing the electronics that change our everyday lives for the better.

You can explore AES’s full selection of test chambers here. If you have questions about RF shielding or any other specification, give us a call. We build standard and custom chambers for companies across a wide array of industries.