Radiated EMI Measurements in Shielded Enclosures

Current standards and specifications require that most case and cable radiation and susceptibility measurements be made in shielded enclosures. However, it is well known that there are a number of serious problems associated with performing these measurements in a shielded enclosure. This paper presents the results from a comprehensive effort to better define the problems associated with field intensity measurements in shielded enclosures and to develop measurement techniques for making satisfactory measurements. Extensive experimental data are presented to show (1) the magnitude of error that can be expected using present measurement techniques, (2) the field distribution in a shielded enclosure as a function of frequency, and (3) the coupling between a source and a probe antenna in a shielded enclosure as a function of frequency and spacing.