Estimation of mode conversion and crosstalk impact from a single-ended aggressor to a differential victim using statistical BER analysis

Increase in the cost of printed circuit board (PCB) with the increase in layer count has led to the design of PCB stack-ups that have broadside coupled signals. The coupling that occurs between the single-ended signal trace coupled to a differential signal traces at various angles and at multiple instances creates a imbalance in the differential signal line thereby generating common-mode signal at the victim receiver. The periodic routing of single-ended trace also generate Floquet modes where the near end crosstalk (NEXT) peaks impacting the signal at the victim receiver. In this paper, various design parameters that impact the eye opening such as number of coupled sections (which dictates the periodicity), horizontal spacing of victim and aggressor, and signaling speeds are included. Different styles of routing of single-ended trace are studied to quantify the impact of differential-common mode conversion and NEXT at the receiver using statistical bit error rate (BER) analysis. Guidelines for best routing practices are developed for the designer to maintain signal integrity.