Teledyne LeCroy TF-DSQ - Manual (Page 23)

TF-DSQ Probe Calibration and Deskew Fixture
TF-DSQ-OM-E RevC 23
Now, let's assume that these probes are applied to signals with the same risetime, but a
different risetime than the one applied by the deskew fixture:
This example clearly illustrates how the application of signals with the same risetime (but
different risetime than the one applied by the deskew fixture) produces a deskew error, unless
compensated. In the previous figure, the green trace is the actual signal applied to the probes
that has a risetime of twice that employed by the fixture. The red and blue traces represent the
trace acquired through the probes and channel due to this edge. Because of the different
risetime applied, there is a small error.
A possible solution to this would be to vary the risetime of the edge applied to the probe by the
fixture; a very difficult design. Despite this difficulty, a variable risetime solution would require
knowing what the measured risetimes would be ahead of time or to measure the risetimes first.