KangSub
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Posts: 9
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hi,
followings are my opinion.
If there are large frequency offset between clock and data, BBPD will produce the random sequence of UP and DN outputs.
BBPD uses at least 3-sample in consecutive 2-UI for phase detection between clock and data and produces valid UP and DN according to the position of data transition. on the other words, BBPD detects the position of data transition relative to that of clock, using consecutive 3-samples in 2-UI. so, the frequency of clock and data have to be equal.
if there exist large frequency offset between data and clock, then, BBPD cannot sample 3-sample in consecutive 2-UI and cannot operate properly. in that case, the 3-samples have no information about the position of the data transition. therefore, the output of the BBPD is not meaningful. if the input data is PRBS, because the probability that sampled bit is 0 or 1 is always same, the UP and DN output of BBPD will also random sequence.
I don't think that Alexander BBPD can detect any frequency information.
thanks,
- KangSub
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