Statistical anisotropy in imperfect electromagnetic reverberation

A probabilistic characterization is performed for a class of field anisotropy coefficients for local random electromagnetic fields. Isotropic stirring (ideal reverberation), anisotropic stirring (polarization bias), and incomplete stirring (line-of-sight coupling or direct illumination) are investigated individually. For small degrees of planar anisotropy or coupling, trapezoidal distributions are obtained, representing first-order departures from ideal rectangular distributions. Distributions for two definitions of total field anisotropy are found to be less sensitive than those for the individual planar anisotropies. The method and results are useful for the calibration and validation of reverberation chambers when field anisotropy requires a separate assessment. Theoretical results are compared to measured data in two chambers.