Prediction of Crosstalk in Ribbon Cables

The prediction of crosstalk in ribbon cables is in­ vestigated. Experimental results are obtained for a 20 wire ribbon cable and compared to the predictions of the multiconductor transmission line (MTL) model. Based on the experimental configuration tested, it would appear that accurate predictions of crosstalk can be achieved in controlled characteristic cables such as these. The prediction accuracies are typically with + 1 dB for frequencies such that the line is electrically short and + 6 dB for frequencies such that the line is electrically long. It was found that the parasitic wires in the cable can have a significant effect (as much as 40 dB) on the coupling between a generator circuit and a receptor cir­ cuit in the cable. Therefore to achieve accurate pre­ dictions in ribbon cables, one must consider the inter­ actions between all wires in the cable. The wire in­ sulation evidently cannot be ignored for frequencies such that the line is electrically long. The impedance of the reference wire cannot be ignored for low frequen­ cies where the common impedance coupling dominates the electromagnetic field coupling.