PCIe connections have one to two ground contacts per differential signal pair. Why is this the case?
On the boards that I have been studying, all of these pins are tied together onto the same ground plane on the board (at least as far as I can tell), so does it really make a difference? They should all be at essentially the same potential, right?
Are there just ground pins interleaved with the signal pairs in order to absorb any potential crosstalk between adjacent pairs? If this is the case, why are you supposed to remove any (internal) ground plane in the contact area?