Application of the FD-TD method to modelling the electromagnetic radiation from heatsinks

Regulations in EMC are continually becoming increasingly stringent, conversely higher clock frequencies in IT equipment and higher switching rates in power conversion equipment lead to an increase in the electromagnetic radiation which the standards aim to control. Shielding forms one effective way of reducing unwanted radiated emissions, but where components need to be mounted externally on heatsinks, for cooling requirements, shielding is not possible. It therefore becomes important to know the radiation properties of a heatsink so that the correct one may be chosen to fit a particular application. This paper discusses the use of finite difference time domain (FD-TD) modelling to map out the radiation patterns from a common type of heatsink and explains how different dimensions of the heatsink affect this radiation. The modelled results are then validated with measurements.