Prediction of radiated emissions from high‐speed printed circuit board traces using dipole antenna and imbalance difference model

Abstract

The ever-increasing clock speeds on printed circuit board (PCB) have enhanced PCB traces to become efficient radiators of electromagnetic energy. Conventionally, the radiated emissions (REs) of electrically short PCB traces are estimated using expressions developed based on electric/magnetic dipole antenna. In this study, a novel method was proposed to estimate RE from electrically long PCB traces. In this method, the differential-mode (DM) RE was estimated using the transmission-line theory and dipole antenna model, whereas the common-mode (CM) RE was computed by a combination of imbalance difference model and a dipole antenna. Conceptually, the electrically long trace was chunked into multiple electrically short segments and the fields of each segment were superimposed to obtain the net radiated fields. Additionally, closed-form expressions were derived to estimate the DM REs from electrically long PCB traces based on dipole antenna model. On the other hand, CM RE was predicted by line integration of CM current distribution which was approximated using imbalance difference model and asymmetrical dipole antenna model. The effectiveness of the proposed method was verified using compact single-sided PCB by comparing the computed results with the measured results taken in a semi-anechoic chamber, and a good agreement with accuracy more than 90% was observed for upper bounds of the REs.