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Eye Diagram different values in measurement for histogram and line plot

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Muhammad Rizwan
Muhammad Rizwan on 12 Jul 2020
Answered: Devineni Aslesha on 24 Jul 2020
Hi
I am trying to obtain an eye diagram for my filter.
For analysis when I use line plot it displays different values for eye height.
BUt when I change it to 2D histogram it displays correct values as can be observed from the eye plot.
My question is that why for the same filter eye measurements are different.
I have attached screen shots and also the simulink file.

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Muhammad Rizwan
Muhammad Rizwan on 12 Jul 2020
Hi Adam ,
Yes both are from same model which is also attached as a simulink file too.
Difference is that one is Line plot in eye diagram and other one is 2D histogram.
Adam Danz
Adam Danz on 13 Jul 2020
2D histograms typically return the number of data points within each 2D bin. I wonder if the eye height is using the bin counts rather than the raw data. That's something you could look into. I'd start at where the eye heigh is computed and compare the inputs when you plot the line vs the hist.
Muhammad Rizwan
Muhammad Rizwan on 13 Jul 2020
I didnot get your answer.What do you mean by "I'd start at where the eye heigh is computed and compare the inputs when you plot the line vs the hist. "
Eye height should be like more than it displays in diagram.Eye height is 3 sigma from both levels .
It is confusing me that data is not that much spreaded as it depicts in eye height.

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Answers (1)

Devineni Aslesha
Devineni Aslesha on 24 Jul 2020
Hi Muhammad,
In the attached simulink model, the Stop Time is 100 sec. So, when you are trying to change the Display Mode to 2D Color Histogram during the simulation process, eye height is different for Line Plot and 2D color Histogram. I tried with the Stop Time of 10 sec and captured the screenshot of 2D histogram plot after the simulation is done and found that eye height is same for both Line plot and 2D color histogram. Try to observe the measurements once the entire simulation is done.
Hope this helps.

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