The effect of grounding on radiated emissions from heatsinks

The paper presents results which demonstrate that radiated emissions from heatsinks are reduced by an amount that depends upon the distribution and impedance of the grounding structure. Results are also presented which show the effect on radiated emissions of the presence of conductors (e.g. PCB tracks) passing under the heatsink. The presence of conductors reduces the effectiveness of the heatsink grounding but, in most case, emissions at high frequencies do not exceed those without conductors attached.