Stirred-Mode Operation of Reverberation Chambers for EMC Testing

TLDR

Stirred‑mode operation of a mechanically tuned reverberation chamber offers a cost‑effective, robust alternative to stepped‑mode testing, but requires proper sampling to capture all independent field configurations at the test point. Optimal sampling is achieved by taking measurements at equal tuner angular increments over a single rotation, and exposure time to each field configuration can be tuned by adjusting the number of samples and the tuner speed. Experimental results show that stirred operation produces spectral data identical to stepped mode regardless of tuner speed (when transient time is short), that a single rotation samples all configurations, yielding a more robust test than the 12‑step stepped approach and reducing testing time.

Abstract

Continuous stirred-mode operation of a mechanically tuned reverberation chamber provides an alternative to stepped-mode operation that is both more cost effective and more robust in many electromagnetic compatibility testing applications. An experimental investigation shows that the spectral information available within the chamber is the same for both the stepped and the stirred operation and is independent of the tuner speed provided that the chamber transient time is small compared to the rate at which the fields change inside the chamber due to the tuner rotation. This is further confirmed for stirred operation at additional frequencies. However, the field must be properly sampled to ensure that all independent field configurations available at the test point within the chamber are included in the spectral analysis. Optimal sampling is obtained when sampling at the same tuner angular position increment over a single tuner rotation at any tuner speed. Equipment under test may be exposed to all available field configurations available within the chamber using stirred operation with a single rotation of the tuner, giving a more robust test than the minimum 12 steps that are used with the stepped operation. Testing time is also reduced. The exposure time to a particular field configuration can be controlled with knowledge of the number of independent samples available in the chamber and by changing the tuner rotational speed.