Comparison of via equivalent circuit model accuracy using quasi-static and full-wave approaches

Abstract

The EMC and signal integrity impact of printed circuit board (PCB) trace discontinuities, such as vias, where the signal is transitioned from one layer to another in the PCB stackup, have become significant recently with the use of very high speed signals in today's systems. If these discontinuities are ignored, significant distortion of the high speed signal can occur, and in many cases, cause data errors. A fast and accurate technique to include the effect of via discontinuities in the typical design process is needed to ensure this distortion is considered if significant Therefore, a simple equivalent circuit for the via discontinuity is needed so that this equivalent circuit can be easily used in the normal signal integrity analysis tools. This paper demonstrates the effect on the equivalent circuit values as the distance between the signal via and the return-current via is increased. Also, the frequency range where a quasi-static based equivalent circuit is accurate or where a full-wave model is required is shown for the various distances between vias.