Screened-Room Measurements on the NIST Spherical-Dipole Standard Radiator

We report the results of a study of measurements of radiated emissions from the NIST sphcrical-dipole standard radiator in several screened rooms. The study serves as a demonstration of possible applications of the standard radiator as well as an investigation of radiated-emissions measurements in screened rooms. The screened-room measurements were performed in accordance with MIL-STD)-462 (1967). Large differences occurred in the field intensity measured at different laboratories and even on different days at the same laboratory. There was a systematic difference at low frequencies between the screened-room results and results obtained in a transverse electromagnetic (TEM) cell, open-area test site (OATS), and anechoic chamber. We also present the results of OATS tests confirming the temporal stability of the standard radiator and measuring the loading effect of a ground plane as a function of distance from the sphere.