The validity of using image plane theory to predict printed circuit board radiation

In order to reduce the radiated emissions of a printed circuit board (PCB), a conductive plane is often placed beneath the PCB. Image theory has been used in the literature to explain why conductive planes have this effect. The validity of using image plane theory in analyzing printed circuit boards is questionable because of the finite size of these planes. Some effects of the conductive planes are due to the additional load which these planes put on the source. This effect is not predicted by image theory