Differential to Common Mode Conversion in Balanced Devices and Systems

The problem of differential mode to common mode conversion in balanced devices and systems is illustrated. The mixed mode S parameters are not suitable to characterize this mechanism and what is more important they do not allow an easy interpretation of common mode and differential mode losses. Mixed mode Z parameters provide the right tool to achieve a better insight into problems related to EMC matters. On the other hand S parameters are more suitable to be measured and to characterize cascaded devices. The mode conversion does not only depend on imbalances in the electrical signal transmission paths but also may be caused by amplitude, delay and waveform skews in differential sources; the combination of imbalances of the differential signals and of the transmission paths generates common mode signals. Simulation results are presented and discussed to illustrate the previous conclusions.