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        Title : Eye Diagram,

 


Eye Diagram



 

Description

An "Eye diagram" calculation is used to display the behavior of a data set over a specific period of time. By superimposing the curve intervals (one interval per period), a visual analysis of the variation of a signal is therefore immediate. The main sought characteristics are the variation in periodicity and the jitter in intensity.

There are two possibilities for the calculation reference :


  • Use of a reference signal whose transition through a predefined level (threshold) is used. It is currently not implemented, but is without difficulty.

  • The window characteristics are determined by the following parameters :
    • Start of the period
    • End of period
    • Periode
    • Number of segments over the period

  • Note : Imposing a number of segments allows for regular sampling, thus facilitating comparisons. Points xn,yn are systematically recalculated.



 

Example

TkFab : this image show the data set on which is applied eye diagram functionality
Data set for "Eye Diagram" function
TkFab : this image show the result of eye diagram functionality on a set of data
"Eye Diagram" result
 

Some code …

TkFab® includes the possibility of writing instructions in meta-language allowing you to create short programs equivalent to several dozen lines of code. It is carried out using the "namespace" concept of the Tcl language.The lines below generate the data as a file in CSV format which is used as a dataset for the "Eye diagram" example.


  • Note : Lines are only clearly visible on a wide screen.

maths clear 1v {} maths create 1v ex1 maths expression1d 1v ex1 -name func1 -xstart 0.0 -xend 0.001 \ -formula { y = (1+(cos(_2pi*(0.5 + (rand()/50.0))*f*$t)/10.0))*sin(_2pi*f*$t) } \ -steps 10000 -algo fixed -var t -val y \ -pnames f -pvalues 10000 maths print 1v ex1 generate_jitter_y_accurate.csv -name func1 -var_units s -val_units "V" return 1


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