On simulating OATS near-field emission measurements via GTEM cell measurements

The use of a gigahertz transverse electromagnetic (GTEM) cell for both near-field and far-field radiated emission testing is considered. The approach is to model the radiation from the device under test (DUT) as due to an equivalent set of multipole moments. A sequence of three, six, or nine GTEM measurements is used to determine the equivalent multipole moments for a particular DUT. The multipole model makes it possible to predict both the DUT free space radiation pattern and the DUT radiation over a ground screen. The correlation between GTEM cell and open area test site (OATS) measurements for the far field case (>30 MHz, 3-m distance) has been examined previously. Correlation of sources in the near field (<30 MHz, 1-m distance) is considered in the present work. Agreement between OATS data and GTEM cell correlated data is better than 2 dB