Maximum Crosstalk Estimation in Weakly Coupled Transmission Lines

Eliminating crosstalk problems in a complex system requires methods that quickly predict where problems may occur and that give intuitive feedback on how best to solve these problems. Solutions for the maximum crosstalk are often used for this purpose. Limit lines for maximum crosstalk in the frequency domain are available in the literature when signal lines are electrically small and weak coupling is assumed; however, little research has been performed for the case where signal lines are electrically large. This paper provides derivations for maximum crosstalk in the frequency domain when signal lines are electrically large and weak coupling applies. The coupling mechanisms are represented by distributed voltage and current sources. These sources result from aggressor circuit voltages and currents as well as mutual terms in the transmission line per-unit-length parameters. The maximum crosstalk expressions for the victim loads are represented by piecewise expressions dependent on the total electrical length of the aggressor circuit and the electrical length of the coupling region. Measurements and simulations are presented, which show the maximum crosstalk estimates can predict the maximum envelope of crosstalk within a few dB.