A Method to Minimize Emission Measurement Uncertainty of Electrically Large EUTs in GTEM Cells and FARs Above 1 GHz

This paper presents an emission measurement technique with reduced uncertainties for electrically large equipment under test (EUTs) in gigahertz transverse electromagnetic (GTEM) cells and fully anechoic rooms (FARs) above 1 GHz. A small and a large EUT were measured and the results obtained in the GTEM cell were validated against those obtained in a FAR. Measurements in a FAR were made, for the small EUT, in the conventional way with an azimuth scan and, for the large EUT, with a limited antenna height scan. Key findings are that similar scanning is required in the GTEM cell and that the three-orthogonal-position (TOP) method of EN61000-4-20 is not appropriate for EUTs that have multilobed radiation patterns. In other words, GTEM cells and FARs are sensitive to directional properties of EUTs, and both methods require further scanning for electrically large EUTs