Fundamentals of Signal Transmission on Interconnects

This chapter presents the major concepts required to understand the movement of signals on transmission lines. The important concept of traveling waves is introduced and the origin of reflections on transmission lines identified. The concepts discussed in the chapter include packaging hierarchy, primary and secondary transmission constants, and transmission line impedances. Interference between the incident and reflected waves, traveling at the same velocity but in opposite directions, causes a ‘standing‐wave’ field pattern to be set up. If there is a signal current there must be a return signal current which will tend to be as close to the signal current as possible to minimize stored energy. The provision of a signal return path is important in maintaining the integrity (i.e., predictable signal waveform) of interconnects. A range of models are used for interconnects depending on the accuracy required, the amenability of the net to modelling, and the frequency of operation.