Numerical analysis of effects of grounded benches on the field distribution in immunity testing

Grounded benches are used in several standards as the common test set up for emission and immunity measurements. While it is understood that the reason for the presence of a conductive topped bench is to provide a consistent electromagnetic environment when performing emission measurements, the paper shows that during immunity measurements the presence of the ground plane can leave large areas of the EUT out of the illumination area. Numerical results are shown for different types of antennas and different configurations. The results show that it is recommended that for immunity measurements the bench be left non-conductive for a better coverage of the EUT. The numerical models are supported by numerical data to validate their results.