Prediction of radiated emissions from high speed PCB traces using travelling wave antenna model

The ever-increasing clock speeds of printed circuit board (PCB) have imposed many challenges on the circuit designers, one of which is to pass the electromagnetic compatibility compliance testing for radiated emissions. It is essential to predict PCB radiated emissions prior to a compliance test with the aim to save cost and time. For high-speed PCBs, their traces are electrically long and thus making them efficient radiators. In this paper, a prediction model is developed based on travelling wave antenna model to predict Differential Mode (DM) radiated emission from a high-speed PCB traces above a ground plane while Common Mode (CM) radiated emission is predicted based on monopole antenna model. Two closed-form expressions were derived to describe DM and CM radiated emissions for electrically long PCB traces. The obtained results, based on the aforementioned models, were validated through comparison with other models and good agreements were achieved. These developed closed-form equations can be employed to develop a software tool that can characterize and quantifies radiated emissions at the design stage.