A Possible Minimum Relevance Requirement for a Statistical Approach in a Reverberation Chamber

Modal overlap in a reverberation chamber (RC) involves, strictly speaking, an infinite number of modes in the field statistics. The degree of overmodedness of an RC is often assessed by introducing an arbitrary reference bandwidth in which a number of overlapping modes is computed. We introduce a statistical model of the field in which the number of modes is rigorously finite. The model is chosen such that the number of degrees of freedom (DOF) of the field can be assessed. The number of DOF is assessed by considering the degree of homogeneity of the average power received by a linearly polarized antenna. It is considered that a statistical approach requires at least a single degree of freedom. Based on this criterion, the minimum frequency at which a statistical approach would make sense is evaluated and compared to the lowest useable frequency (LUF) commonly considered in EMC.