Using GTEM for electromagnetic emission measurements: experiments in test result correlation

Electromagnetic emissions from a digital broadband source were measured in 30-1000 MHz frequency band using different EMC test facilities: GigaHertz transverse electromagnetic field cell (GTEM), two open area test sites (OATS), and a 3 m site-size RF absorber lined room (AR). While the mean values of the variance between the respective data obtained at these facilities were around 6 dB, the difference between the individual readings could exceed 11-15 dB, confirming the limited character of correlation. On the other hand, the disparities between the GTEM measurement results versus OATS and AR, were of a similar order comparing to those between the OATS and AR, or even between different OATS. Several reasons for these disparities are investigated, including inherent specifics of the facilities, EUT positioning, and cable manipulations