Design

This is a true story. When I first joined IBM as an EMC engineer, my new manager handed me a document titled ‘EMC Design Process at IBM’ and asked me to comment. I quickly read the short document that basically said that the EMC engineer would provide the design engineers a list of EMC rules, which would be largely ignored.

Imagine for a moment that you are trying out a brand new car: you slide into one of the ergonomic seats, start the engine and, to make things perfect, would like to listen to some music. However when you switch this on, you suddenly notice interesting side effects. The light comes on in the passenger compartment, for example. Or the radio starts whistling and whimpering.

This article investigates the impact of ground vias placed in close proximity to high speed differential signal vias and the resulting differential mode to common mode conversion. The work shows the influence of the distance between ground (GND) vias and differential signal (Diff. SIG.); the effect of the asymmetrical configuration of the GND vias; the impact of the dielectric thickness and the number of transitions between the planes.