The Role of the Ground Reference in Reducing Unwanted Electric Coupling Effects

This paper presents the results of theoretical, numerical and experimental comparisons in the investigation on the role of the ground conductor which is used as the reference electrode in many experimental situations and, notably, in ground-referenced tests and measurements in the EMC technology. It is demonstrated that a real (finite-size) ground structure can be considered of practically infinite extent insofar as its capacitance to infinity is sufficiently larger than the capacitance of the hot electrode to infinity. For instance, when the ground capacitance to infinity is about 150 times the capacitance to infinity of the hot electrode (corresponding to a 6 to 1 ratio of the respective dimensions) then 90 % of the hot electrode charge is induced on the ground.