Design and verification of differential transmission lines

Differential signaling is a popular choice for multi-gigabit digital applications such as FiberChannel, Infiniband, OIF, RapidIO, and XAUI. This is due to the fact that differential signaling has the ability to reject common mode noise such as cross talk, simultaneous switching noise, power supply and ground bounce noise. To support differential signaling, differential transmission lines are required. There are several ways of designing differential transmission lines on a conventional printed circuit board (PCB). These include microstrip line, edge coupled stripline, and broadside-coupled stripline. This paper describes a methodology for designing and verifying differential transmission lines on PCBs. The electrical performance of these three differential transmission lines is evaluated in both the frequency and time domain. The practical consideration of manufacturing variation is also examined. Finally, accurate HSPICE w-element models are generated for time domain transient simulations.