Modeling broadside coupled traces using equivalent per unit length (Eq PUL) RLGC model

Abstract

Increases in printed circuit board (PCB) cost is leading to denser routing of high speed signal traces and this, in turn, is increasing the crosstalk among the traces. The crosstalk between the broadside coupled traces in adjacent layers is becoming an important factor to account for as the signal speeds increase. The coupling between parallel broadside coupled traces can be modeled using multi-conductor transmission line theory based on telegrapher equations using equivalent per-unit-length (Eq PUL) resistance, inductance, capacitance, and conductance (RLCG) matrices. The same approach is not applicable for the traces crossing at an arbitrary angle. A fast methodology to develop Eq PUL RLGC models that captures the coupling physics of broadside coupled traces crossing at an angle based on geometrical parameters of the stackup, and the dielectric material properties is proposed based on the idea presented in [1]. In this paper, validation of these equivalent models is done by estimating the crosstalk impact on eye opening at a specified bit error rate (BER) at different signal speeds and results are compared against full wave models.