Christopher White, Signal Integrity Engineer, Cray Inc.
Andrew Becker, Signal Integrity Engineer, Cray Inc.
Jim Fitzke, Signal Integrity Lab Engineer, Cray Inc.

Intra-pair skew in differential signaling has become important in current signal integrity analysis due to its impact on insertion loss and crosstalk in high-speed networks. PCB skew is often the result of design length variation, manufacturing tolerances, and weave effect. Here we have estimated the effects of generic intra-pair skew using transmission line analysis. Our lab measurements from twinaxial cable and PCB test vehicle designs show the relationship between skew and differential signal amplitude, reliably out to 20GHz. We have correlated our analytical estimates to these lab measurements, allowing us a means to predict a maximum tolerable intrapair skew.