Michael Steinberger, Distinguished Member of Technical Staff, Signal Integrity Software
Stephen Scearce, High Speed Design Group Manager, Cisco Systems
Douglas White, High Speed Design Specialist, Cisco Systems

Vias play a critical role in the high-frequency electrical behavior of packages and printed circuit boards. Although measured data and electromagnetic solvers can be used to study via electrical properties, a clearer description of the underlying physics would make engineering judgment concerning vias more effective.

This paper introduces a simple experiment and corresponding textbook solution for radial TEM waves, which demonstrate the physics of vias. Extensions of this experiment show how the underlying physical model can be used to explain the behavior of differential vias, ground vias, and via antipads.