A Comprehensive and Practical Way to Look at Crosstalk for Transmission Lines with Mismatched Terminals

Abstract

The analytical formulas for crosstalk due to backward and forward coupling were originally introduced in 1963 [1]. In 2016, the formulas were extended for asymmetrical traces [2]. But all previous approaches assume perfectly-matched terminals, which limits the usage of these equations. In this paper, we re-define the far-end crosstalk (FEXT) as a combination of several components generated by different coupling and reflection mechanisms. A new set of crosstalk estimation formulas is developed to calculate the contribution of each component. Because the influence of mismatched terminals is introduced, the proposed method has much better accuracy than the traditional approach, which estimates FEXT by using forward coupling noise alone. In addition, the proposed equations use per-unit-length inductance (L) and capacitance (C) metrics as inputs instead of S-parameters. Since L and C can be calculated using analytical formulas, the new approach provides a practical and fast crosstalk estimation for engineering designs, avoiding the time-consuming numerical full wave 2D or 3D simulations.