IEC 61000-4-3: How Radiated Immunity Testing Works
The setup, levels and chamber requirements of IEC 61000-4-3, the test that measures a device's immunity to radio transmitters and mobile phones.
3 min readOctober 17, 2026
What Do Absorbers Do?
The walls of an anechoic chamber are a metal shell; it blocks outside signals but also reflects signals generated inside. A reflected signal reaches the antenna by a second path and spoils the measurement. Absorbers eliminate these reflections by converting them into heat.
No absorber performs equally well at every frequency. That's why chamber design starts with the frequency range to be tested, and then the absorber that covers that range most economically is chosen.
Ferrite Tiles: The Low-Frequency Answer
Ferrite tiles are ceramic plates a few millimeters thick, bonded directly to the wall. They are very effective at low frequencies between 30 MHz and 1 GHz and take up almost no space, preserving the chamber's internal volume.
Their drawbacks are weight and weak performance at high frequencies. Covering a wall with ferrite tiles means tons of load, so the structure is checked carefully during building preparation.
Pyramid Absorbers: The High-Frequency Answer
Pyramid absorbers are made of carbon-loaded foam. Their pointed shape slows and absorbs the incoming wave gradually. They work very well at high frequencies; to be effective at low frequencies, however, they must be very long.
One-meter pyramids take a serious bite out of the chamber's internal volume. As a result, chambers using only pyramids need a larger building for the same test distance.
The Hybrid Solution
Most EMC chambers today use hybrid absorbers, with short pyramids added on top of ferrite tiles. The ferrite handles low frequencies and the short foam handles high frequencies, giving broadband performance and a reasonable chamber size.
In fully anechoic chambers working at very high frequencies, such as for antenna measurements, pyramid-only absorbers are usually preferred. We decide together during the survey which combination fits your test plan.
Frequently Asked Questions
Do absorbers degrade over time?
Pyramid foams are sensitive to impact and moisture; crushed pieces are replaced. Ferrite tiles last long, but cracked tiles can reduce performance.
Are absorbers fire resistant?
Quality absorbers are made with flame-retardant additives and tested to the relevant fire standards. Material certificates are included in the handover file.
Can an existing chamber be upgraded by changing absorbers?
Yes. When higher-frequency testing is needed, the chamber's operating range can be extended by changing the absorber type.
Let's Find the Right Solution for Your Project
Get a QuoteYour free site survey and quote will be ready within 24 hours.