I have one PCIe test adapter routed not as single ended, but as diff pair.
After deskew this adapter with open other ends, S11 phase goes up with frequency.
I think, something wrong goes with deskew, can single ended lines be deskewed then routed as diff pair?
here i have Test Adapter with differential routed traces
Here are another adapter, single ended routed, that works without problem.
I want to be sure that xtalk causes the problem, any ideas?