Radiated emissions monitoring entails measuring the electromagnetic field intensity of emissions generated by your electrical product. Emissions are implicit in the switching voltages and currents of any digital circuit; the only question is how high the emissions are and if they conform with the emissions limits.

Radiated emissions limits differ depending on geographical area and product class. The limits in Europe and North America are similar but not the same. Hence it is possible to meet FCC requirements but fail European limits.
When the DUT (Device under test) is subject to an industrial standard, the limits are often more relaxed as compared to residential requirements. Certain product categories like military have test limits which are much more expansive and stricter to comply with than commercial or residential devices.

Maximization is a measurement technique used to determine the maximum amplitude of the product’s emissions. Once we’ve identified the frequencies with the highest emission, we’ll run a maximization process. All testing is performed in a 10m EMC chamber.

For testing radiated emissions from electrical devices, there are two main types of test sites: Open Area Test Site (OATS) and Semi-Anechoic Chamber (SAC). These test sites aim to reliably calculate your product’s emissions to ensure that they meet the applicable limits.

They are usually designed to meet the specifications of ANSI C63.4 (for North America and elsewhere) and CISPR 16-1-x (for Europe and elsewhere).
OATS are setup in an open field and in the current age of wireless devices clients and test engineers face many challenges when using OATS to perform compliance testing.

SAC is similar to OATS however it is housed within a shielded (metal) space.

This is very useful because it reduces the background (ambient) radio signals, making it much easier to differentiate between what is coming from the client’s product and what is coming from the background signals.

Although more expensive chambers provide an excellent solution for measuring radiated emissions in an otherwise noisy environment.