Investigation of the imbalance difference model and its application to various circuit board and cable geometries

The imbalance difference model introduced by Watanabe is a method for modeling how differential-mode signal currents are converted to common-mode noise currents. A parameter called the current division factor or imbalance factor uniquely defines the degree of imbalance of a transmission line. The imbalance difference model shows that changes in the imbalance are responsible for differential-mode to common-mode conversion. This paper explores various circuit board and cable geometries to illustrate how the imbalance difference model would be applied, and to determine how well common-mode currents obtained using the imbalance difference model compare to full-wave calculations.