In the world of high-speed digital design, clock rates are increasing at a dramatic pace. Gigabit per second data rates are creating signal integrity problems for printed circuit board structures such as backplanes, microstrip traces and interconnects. While simulation tools allow helpful insights into predicting structure performance, more test and measurement tools are needed to measure and verify the actual response to fast edge speeds. Time Domain Reflectometry is one of the tools used most frequently by digital design engineers to relate physical interconnect structures to such parameters as characteristic impedance, reflection coefficient, propagation velocity and edge effects.