SDI Eye and Jitter Measurements
How-to Guide
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Overshoot within the eye display is likely due to reflection along the signal path and can be due to
incorrect terminations. Figure 10a show a large overshoot from the output of a device that was due to
reflections along the secondary output of the device. In this case the unterminated secondary output
was terminated with a 75-ohm termination in order to resolve this issue. The user will have to test the
signal at various points in the chain to determine from where the reflections are occurring, this could
occur at a patch panel, barrel connector or problem with a cable or connections.
Unequal rise and fall time of the transitions causes a shift in the 50% point of the eye display as shown
in Figure 10b. In this case the rise time is longer than the fall time of the signal and this caused a shift in
the cross point of the transition. This type of effect may occur with an optical to electrical converter or
other processing devices.
Figure 10a.
Overshoot of eye display.
Figure 10b.
Unequal Rise and Fall time.
Both of these type of effects in of themselves do not cause a problem with recovery of the clock and
data, as you can see no CRC errors occurred in this signal. However these types of effects can
accumulate with other errors to lower the threshold of the signal and cause CRC errors to occur failure
of the transmission of the signal.
