Mixed-Mode S-Parameter Measurements for Determination of Cable Coupling

Single-ended S-parameters are used to quantify electromagnetic coupling, or crosstalk, between cables. The use of this measurement technique is demonstrated on a case where crosstalk occurs between two wire pairs above ground. S-parameter measurements involve no elements that introduce frequency restrictions, such as baluns or current clamps. Moreover, by measuring or simulating all combinations of S-parameters and converting these to mixed-mode S-parameters, not only differential-mode (DM), but also common-mode (CM) and mode-conversion S-parameters are obtained. When only the coupling between a specific combination of cables is desired, it is sufficient to measure only a small subset of all S-parameters. Finally, the relation between crosstalk as defined in the standards and the obtained S-parameters is discussed.