Applications of multiconductor transmission line theory to the prediction of cable coupling. Volume 5: Prediction of crosstalk involving twisted wire pairs

A transmission line model of the twisted wire pair is presented which may be used to compute electromagnetic coupling between the twisted wire pair and other circuits. The model is derived by representing the transmission line for the twisted wire pair as a cascade of uniform loops and 'abruptly' nonuniform twists. The overall transmission line matrix is found by cascading the chain parameter matrices, which represent the loops, with the permutation matrices, that represent the twists. Comparisons are presented between the twisted wire pair, the straight wire pair, and the single wire circuit configurations to determine the relative effectiveness in the reduction of electromagnetic coupling. Experimental results are compared to the model predictions which verify that the chain parameter model is accurate to within + or - 3 dB for frequencies such that the line is electrically short (i. e. 1/10 lambda). Finally a second model, the low frequency model, is presented and is shown to be as accurate as the chain parameter model in the prediction of coupling at low frequencies. This low frequency model is very appealing in that it is conceptually much easier to model and also less time consuming, computationally.