Datasheet

AD9577 Data Sheet
Rev. 0 | Page 26 of 44
Therefore, to accurately estimate the TJ p-p, separate
measurements of the rms value of the random jitter (RJ rms)
and the peak-to-peak value of the deterministic jitter (DJ p-p)
must be taken. To measure the RJ rms of the clock signal,
integrate the clock phase noise over the desired bandwidth, with
spurs disabled (that is, removed) from the measurement. If the
DJ spurs were included in the measurement, the DJ
contribution would also be multiplied by 14.06 in Equation 2,
leading to a grossly pessimistic estimate of the total jitter. This is
why it is important to measure the integrated jitter with spurs
disabled. Due to the 14.06 factor in Equation 2, the spurious DJ
components on the clock output only have a small impact on
the TJ p-p measurement and, consequently, the system BER
performance. Therefore, it is clear that the DJ component (that
is, the spur) should not be added to the rms value of the random
jitter directly. However, if the phase noise jitter measurement
was preformed with spurs enabled, this is exactly what the
measurement would be reporting. For more background
information, see Fibre Channel, Methodologies for Jitter and
Signal Quality Specification-MJSQ, Rev. 14, June 9, 2004.