What are Electromagnetic Reverberation Chambers and Why Using Them?

In the world of electromagnetic compatibility (EMC) testing, there are a variety of tools and techniques used to evaluate the impact of electromagnetic radiation on electronic equipment. One such tool is the electromagnetic reverberation chamber, which has been used in various industries to test equipment for its EMC characteristics.

There are two main advantages to using reverberation chambers for EMC testing: they can generate high field strengths, and they can illuminate a device under test (DUT) from all angles. Within the chamber, a high number of modes are excited wile the boundary conditions are changed by stirring methods [1]: This can be done by a moving mechanical object like a moving wall as seen on the photo from the inside of TU/e’s reverberation chamber, or shaking if the chamber consist out of conductive fabric. The field follows a known distribution and is even at every point within the chamber’s working volume, when averaged over a sufficient number of stirring cycles [2]. Fields are randomly incoming from any direction and with random phase.
These advantages make reverberation chambers ideal for testing equipment close to real life scenarios. Reverberation chambers can also be used to evaluate the shielding effectiveness of materials and cables or for over the air testing of wireless devices [3]. Vice-versa, reverberation chambers can also be used to determine the total radiated power of a DUT. If compliance with a standard is anticipated, EMC testing with reverberation chambers can be found in IEC 61000-4-21:2011.

Advantages of using reverberation chambers over traditional techniques such as scans in anechoic or semi-anechoic chambers, are lower testing times and installation cost, compared to anechoic and semi anechoic chambers. The most affordable version of a reverberation chamber is by far the Vibrating Intrinsic Reverberation Chamber (VIRC) which consists out of a tent made from conductive fabric, which is shaken for stirring. This reverberation chamber can also be scaled up easily to fit trucks, planes or parts of ships. Also, narrow beams are not missed when using this technique. However, at low frequencies below approximately 300 MHz, other techniques need to be utilized because physics dictate that a chamber had to be unreasonably large to properly function as reverberation chamber.
Reverberation chambers are successfully used in industry.

In conclusion, electromagnetic reverberation chambers have proven to be an important tool for EMC testing in a variety of industries. Their ability to generate high field strengths and to illuminate objects from all angles makes them ideal for testing real-life equipment, or to catch the whole radiated emissions of a DUT. While they may not replace traditional test sites in the lower frequency bands, they providede a more accurate reflection of the actual environments in which the equipment will be used, scale significantly better with DUT size and are much more cost effective than anechoic or semi anechoic chambers.

[1] Serra, R., Marvin, A. C., Moglie, F., Primiani, V. M., Cozza, A., Arnaut, L. R., Huang, Y.,
Hatfield, M. O., Klingler, M., & Leferink, F. (2017). Reverberation chambers a la carte: An
overview of the different mode-stirring techniques. IEEE Electromagnetic Compatibility
Magazine, 6(1), 63–78. https://doi.org/10.1109/MEMC.2017.7931986 

[2] Serra, R. (2017). Reverberation chambers through the magnifying glass: An overview and
classification of performance indicators. IEEE Electromagnetic Compatibility Magazine, 6(2),
76–88. https://doi.org/10.1109/MEMC.0.7990003  
[3] Hubrechsen, A., Remley, K. A., & Catteau, S. (2022). Reverberation Chamber Metrology
for Wireless Internet of Things Devices: Flexibility in Form Factor, Rigor in Test. IEEE
Microwave Magazine, 23(2), 75–85. https://doi.org/10.1109/MMM.2021.3125464