Teledyne LeCroy SDA III-CompleteLinQ - Manual (Page 55)

Operator's Manual
populations or normalizations. Shown with the Q-scale transform is the best straight line fit ( the thin
white line).
Noise Parameters
Touch the Noise Parameters button on the Noise Measurement dialog to display the Noise Parameters
mini-dialog.
NOTE: Noise measurements are computed using the dual-Dirac model chose in the Jitter Parameters
mini-dialog.
Show Rn - displays the random noise result. This is calculated either from the dual-Dirac analysis, or from
the RUnBUn spectrum, depending on the selection for the model to be used in the Jitter Parameters
dialog.
Show Dn - displays the deterministic noise result. This is calculated from dual-Dirac analysis analysis.
Show Tn(BER) - displays the total noise at the selected BER value. This corresponds to the noise one
would find when extrapolating the measured noise using one of three dual-Dirac models.
Show ISIn - displays the intersymbol interference "noise". This parameters quantifies the vertical extent
of ISI. (ISI is highly deterministic, but can look very much like noise, especially when looking at normal
data rather than a strictly repeating pattern.)
Show Pn - displays the periodic noise. This is the peak-to-peak height of the Pn inverse FFT.
Show EH(BER) - displays the eye height at the selected BER, calculated as the eye amplitude -Tn.
Show EW(BER) - displays the eye width at the selected BER, calculated as the unit interval width -Tj.
Log10 BER - This control sets the BER at which the Tnis reported, 10^-12 by default.
Turn Off All - Touch this button to turn off all noise parameters.
Noise Measurement Theory
Noise measurements and views are calculated using the algorithm described below.
1. Measuring noise requires an a priori knowledge of what component of the input waveform is signal
rather than noise. This is done via pattern analysis. In the simple case of a strictly repeating pattern,
such as PRBS7, which includes 127 bits, the oscilloscope can find the bit pattern in the waveform, and
identify all occurrences of any particular bit. When the data is not a repeating pattern, the oscil-
loscope can look for repetitions of shorter runs to identify patterns By averaging the waveforms for
each bit in a pattern, (while taking into account small variations in the bit width due to PLL tracking),
a noiseless version of the pattern can be constructed.
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