Is it possible to display an eye pattern on my oscilloscope?

Question:

Is it possible to display an eye pattern on my oscilloscope?

Answer:

Any real-time scope can display an eye with varying degrees of clarity. The faster the scope is able to re-trigger, the clearer the eye.

To display an eye, first adjust the settings so that you are able to see one period and center it in the display. We are using a signal at a data rate of 200MHz (1 UI = 5nsec), so we will set our timebase to 1nsec/div.

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Figure 1: Your data signal

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Figure 2: One period of your data signal

Now adjust the position or horizontal delay so that the period being viewed is not the edge being triggered. It is usually best to center on the third or fifth UI after the trigger. In this case the third UI starts on 15nsec, so the center of the UI will be 15nsec + ½ of a UI = 17.5nsec.

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Figure 3: Adjust the horizontal position or delay to the third or fifth UI

Now go into the display menu and turn on variable persistence to see both the positive and negative transitions of the period at a given unit interval.

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Figure 4: Final eye diagram using persistence mode

In addition, you can use FastAcq mode or WaveformDB mode to create a color graded display of your eye.

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Figure 5: Eye diagram using FastAcq mode

 

FAQ ID : 63766

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