Circuit interpretation and perturbative analysis of differential-to-common mode conversion due to bend discontinuities

In this work, the mechanism of differential-to-common-mode (CM) conversion arising in differential interconnects due to bend discontinuities is investigated. A circuit interpretation of the phenomenon is provided in terms of lumped sources of interference included into the equivalent CM circuit. The obtained circuit model, assessed through full-wave simulation, allows inferring analogies and differences with respect to other sources of CM generation such as asymmetries and non-uniformities of the line cross-section, possibly occurring due to the manufacturing process. It is shown that the bent section can be interpreted as a local perturbation of an ideally uniform and symmetric microstrip cross-section and, as such, included into a more general simulation framework based on a perturbative approach aimed at the CM prediction in differential interconnects.