Sensitivity of mode conversion in geometrically unbalanced coupled differential lines

In this work, the generation of common-mode (CM) currents and voltages in a pair of differential lines (DLs) running parallel each other, in close proximity, is investigated resorting to multi-conductor transmission-line theory and modal analysis. Particularly, the assumptions of weak coupling and weak imbalance are combined to derive a simplified prediction model able to put in evidence the twofold contribution to mode conversion due to (a) asymmetries affecting the line cross-section, and (b) effect of proximity between the two DLs. Sensitivity of mode conversion to the above-mentioned imbalance factors is then investigated by numerical simulations.