Eye Measurements - Agilent Technologies N4906B Serial BERT User Manual

Evaluating Results
162

Eye Measurements

The purpose of eye measurements is to measure the eye height and
width of the incoming data signal at specific alignment BER
thresholds. This information is displayed on a representation of an eye
diagram.
Eye Measurements – Procedures
Eye measurements are made each time the Auto Align, Clock/Data
Center, or 0/1 Threshold Center functions are used.
To analyze the results:
1 View the graph and table in the Eye Results window.
This window provides detailed information on the calculated eye.
See "Eye Measurements – Reference" on page 162.
2 Analyze the results by observing changes in the eye results due to
the following adjustments:
– Make changes to your device or measurement setup.
– Run auto-search functions at different BER thresholds.
This will allow you to see the eye margin at specific BERs and
construct basic eye contour information.
3 Change the sampling point in the Sampling Point Setup window.
See "Sampling Point Display" on page 108 for details.
Eye Measurements – Reference
Eye results are displayed for the Current Align and Previous Align
process. They are also graphically displayed on a representation of an
eye diagram.
Eye Width and Height
Eye width is the inside horizontal opening of the data eye in an eye
diagram. This measurement is made by the error detector after an
Auto Align or Data Center. The eye width at the current 0/1 decision
threshold is displayed on a simulated eye diagram. The left and right
eye edges are determined by the user-defined BER threshold. Different
BER thresholds will produce different eye width results.
Agilent N4906B Serial BERT, User's Guide, October 2005
Eye Measurements