Electromagnetic radiation susceptibility test risk assessment in a reverberation chamber

Background Radiated susceptibility testing of equipment under test (EUT) in a reverberation chamber uses a finite number of independent stirrer positions. Because the field strength varies randomly, a susceptible EUT may not encounter a sample above its susceptibility threshold and may therefore be judged compliant.

Purpose This study develops a statistical framework for threshold estimation and missed-detection risk assessment using total-field and single-polarization-field metrics.

Methods The total electric-field magnitude was modeled by a chi distribution with six degrees of freedom, while a single orthogonal component was modeled by a Rayleigh distribution. The threshold was estimated from the proportion of stirrer positions at which the EUT remained functional. Monte Carlo simulation was used to determine a correction coefficient for finite-sample bias and to evaluate missed-detection risk. An equal-quantile method was used to relate the two field metrics.

Results More independent stirrer positions reduced the relative standard deviation of the threshold estimate, and the correction coefficient approached unity. For 30 stirrer positions, with 28 positions passing the test, the corrected total-field threshold was 3.2865 V/m. As the total-field scale parameter increased from 0.9 to 1.25, the failure probability increased from 3.8% to 32.9%, while the missed-detection risk decreased from 31.206% to 0.001%. For the single-polarization field, the corresponding probability increased from 4.2% to 19.3%, and the risk decreased from 27.691% to 0.142%. The conversion coefficients were 1.520, 1.450, and 1.351 at quantile probabilities of 0.90, 0.95, and 0.99, respectively.

Conclusions A higher test field or more independent stirrer positions reduces the missed-detection risk. The conversion between total and single-polarization fields depends on quantile probability, so a fixed factor is not appropriate. The framework supports the selection of field metrics, test levels, and stirrer-position numbers for EUTs with different polarization responses.