LeCroy DDA 7 Zi series, Руководство оператора

Страница: 423 / 544

Operator's Manual
WP700Zi-OM-E-RevA
422
eyeBER
EyeBER is the estimated bit error rate from an eye diagram. It is calculated using the intersection of the
distribution of the one and zero levels. EyeBER differs from
BER in that eyeBER is calculated from Q-factor and
is, therefore, based on signal-to-noise ratio; BER, on the other hand, is based on jitter.
Jitter Measurement
Jitter is measured by the relative variation in the location in time of the transitions of the signal level across a
specific level. For clock signals, the relative time between threshold crossings (rising-to-rising or falling-to-falling)
is measured. Data signals, on the other hand, generally require the measurement of the relative positioning of the
data signal to the sampling clock, which is related to setup and hold time. Because of its random nature, jitter is
normally described in terms of its probability density function (PDF).
Figure 5-36. Setup and hold time requirement for error-free operation. Data transitions within the setup
and hold time (gray area) will result in bit errors. Time interval error (TIE) is the time difference between
clock and data edges. The PDF of TIE is a measure of the probability of an edge occurring during the
setup and hold time.