A Probabilistic Interpretation of the IEC 61000-4-21 Threshold Levels for Field Uniformity in Ideal Reverberation Chambers

Statistical field uniformity is the main property of reverberation chambers. In many key and seminal works, it is even the way reverberation chambers are defined. The IEC 61000-4-21 proposes a particular metric to assess the performance of reverberation chambers based on field uniformity. It is of crucial importance to understand, interpret and use the metric in a sound and reliable way. This work proposes a probabilistic interpretation of the field uniformity metric in the IEC standard, which allows to provide the defined threshold with a solid rationale. An important and striking finding is the need to provide different limits to the per axis measures of field uniformity (i.e. sx, sy and sz) than for the total field uniformity (i.e. a tot).