Crosstalk Prediction Research Articles

Prediction of Crosstalk Involving Twisted Pairs of Wires-Part I: A Transmission-Line Model for Twisted-Wire Pairs

A transmission line model for predicting electromagnetic coupling (crosstalk) involving twisted-wire pairs (TWP) is developed. The twisted pair is modeled as a cascade of loops consisting of uniform two-wire sections with abrupt interchanges of wire positions at the ends of each loop. Experimental results are obtained for the coupling between a single wire above ground and a twisted pair above ground. The experimental correlation with the model predictions indicates that the simulation model is typically accurate within 3 dB for frequencies such that the total line length is less than 1/ 10 of a wavelength. For higher frequencies, the model tracks the experimental results quite well although the prediction error is somewhat larger.

Prediction of Crosstalk in Ribbon Cables: Comparison of Model Predictions and Experimental Results

The prediction of crosstalk in ribbon cables is investigated. 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 these controlled-characteristic cables. The prediction accuracies are typically within ±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 circuit in the cable. Therefore, to achieve accurate predictions in ribbon cables, one must consider the interactions between all wires in the cable. The wire insulation evidently cannot be ignored for frequencies such that the line is electrically long. The impedance of the reference wire cannot be ignored for low frequencies where the common-impedance coupling dominates the electromagnetic-field coupling.

Improved Simulation of Pulse Propagation Between Digital Circuits

An improved simulation of pulse propagation between integrated digital circuits is presented. Two novel improvements associated with the inverse Laplace transform used are presented; 1) the introduction of two-dimensional weight factors σ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n,m</sub> and 2) the use of a shifting parameter a. The algorithm proposed is very fast and saves considerably on computer memory. Fast Fourier transform (FFT) techniques are also employed. The computed results agree well with the experimental observations using TTL gates. The technique deals with arbitrary input waveforms, lossy lines, aperiodic tap-off loads, and is extended to large large-scale integrated (LSI) digital systems and crosstalk prediction.