I made some jitter measurements of my high speed serial link yesterday. Now i'm analysing the jitter sources, and found out, my random jitter is often not around zero, most time about -1 .. -0.5ps.
What's the reason for a not 0 mean of the random jitter? The pictures show a plot of the random/periodic jitter and the total jitter. The scope cannot give a seperate plot for random jitter and periodic jitter, but the second should be similar to a dual dirac function, so symetric around 0. So why is my RJPJ not around 0?
The TJ is a convolution from RJPJ with Data dependend Jitter(DDJ). DDJ is caused from a PRBS-7.
Edit: I am measuring differential transceiver of a fpga, connected by two skew matched cables. There is no "known" asymmetry in my measurement. If this would be static asymmetry, every measurement would have been an equal RJ, i think. I have a 16Gbit/s NRZ signal, the cables are rated up to 18Ghz, the connectors on the Board 12GHz.