A statistically uniform E-field is created in a reverberation chamber by moving mechanical stirrers to vary boundary conditions. The uniformity of the spatial electric-field distribution in an ideal reverberation chamber can be theoretically estimated by calculating the probability density function of its distribution. However, uniformity in an actual chamber is affected by the dimensions of the chamber and the structure of the stirrers. We experimentally and theoretically evaluated the effect of stirrers on the spatial uniformity of the average, median, and maximum electric-field distributions. When the dimensions of a chamber equipped with effective stirrers are large compared to the wavelength at the operating frequency, that is, when resonant modes above approximately 105 exist below the operating frequency, the spatial uniformity experimentally evaluated agrees well with theoretical values estimated by calculating the probability density function of their distributions.

TEM-mode electric field uniformity on the transverse plane that was perpendicular to a floor conductor of a GTEM (gigahertz transverse electromagnetic) cell, and the usable test volume in the cell, were evaluated both theoretically and experimentally at frequencies of up to 1 GHz. Electric fields in the GTEM cell were calculated by using the FD-TD (finite-difference time-domain) method. The fields were measured by using an optical E-field (electric field) sensor in order to confirm the calculation result. CISPR/A (CISPR: Comite International Special des Perturbations Radioelectriques) and IEC (International Electrotechnical Commission) SC77B proposed in their committee draft that the usable test volume was 0.6W 0.33h, where W and h were a width of the septum (inner conductor of the cell) and a distance between the septum and the floor conductor of the cell, respectively. We found that the usable test volume, i. e. the maximum width and height of an EUT, by the committee draft are reasonable and applicable for a GTEM cell.