The Concept of Weak Imbalance and Its Role in the Emissions and Immunity of Differential Lines

In this letter, the phenomenon of mode conversion as the basis of radiated emissions (RE) and radiated susceptibility (RS) of differential-line circuits terminated with not-perfectly balanced loads is investigated. To this end, the concept of weak imbalance of line terminations is introduced, and its fundamental role in RE and RS is evidenced by resorting to modal analysis and to the concept of the dominant mode. This leads to simple equivalent circuits in which mode conversion is represented by dependent sources. Although here it is applied to RE and RS prediction, the proposed approach has general value and the potential to readily explain and quantify the role of imbalance in systems involving differential lines.