Effective channel budget technique for high-speed channels due to differential P/N skew

It is understood very well that at 20Gbps and beyond, P/N skew from fiber weave effect in printed circuit board (PCB) has to be taken into account. Several studies have been done to measure and quantify the effect of glass weave but very few have offered techniques to budget for P/N skew. System companies need an effective way to capture glass weave skew and budget for it in channel designs. Using transmission line theory, we analytically calculate differential loss due to P/N skew, study the effect of P/N skew on eye performance for SerDes IP and explore dependency of P/N skew on PCB materials. This paper studies effect on S-parameters, SerDes eye performance due to skew that can help SI engineer to effectively budget for P/N skew as part of channel link budget.