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Eye diagram

nevinalex1234

 hi

I have been trying to plot eye diagrams in cadence. The command eyediagram(signal,start,stop,period) is the format. But i am not able to control the no of eyes in my diagram. Say i run my simulation from 0 to 10u and my input clk is 5Ghz, typically to get a SINGLE EYE, i should give 200p as period rite ? I have added a 25p, 25p rise time fall time for it. But the thing seems going crazy.

Any ideas whats bugging ?

Parents

  •  Hi andrew,

    I adjusted my  start time and i got something like this.

    http://www.4shared.com/photo/CnTvTD-b/eye.html

    This is what i wanted. When i try to confirm the same design in matlab (extracting the data to matlab and using commscope.eyediagram), i am not getting the same eye, there are a set of parameters,

     eyeobj= commscope.eyediagram('SamplingFrequency', 10e9, ...
                             'SymbolsPerTrace', 2,...
                             'SamplesPerSymbol', 10, ...                       
                              'MinimumAmplitude', -1, ...
                              'MaximumAmplitude', 1, ...
                              'AmplitudeResolution', .001, ...
                              'MeasurementDelay', 0, ...
                              'PlotType', '2D Line', ...
                              'PlotTimeOffset', 0, ...
                              'RefreshPLot','on',...
                              'ColorScale', 'linear');
    eyeobj.update(data);

    Basically i am trying to convince that the eye diagram plot from matlab and cadence are one and the same. But what are the parameters that i have to additionally give to see the same eye diagram. I have given samples per symbol as 10, but in my earlier post, i have asked reg sampling frequency in cadence, you had told that there is no such thing (http://www.cadence.com/community/forums/T/23319.aspx). In that case what will be my Samples per Symbol ? I hope i am clear

    Currently with the given parameters, i am getting a matlab plot like this which is not the same as the cadence one, atleast in first look.

    http://www.4shared.com/photo/7uYbyIPm/matlabeye.html
     

     

     

Reply

  •  Hi andrew,

    I adjusted my  start time and i got something like this.

    http://www.4shared.com/photo/CnTvTD-b/eye.html

    This is what i wanted. When i try to confirm the same design in matlab (extracting the data to matlab and using commscope.eyediagram), i am not getting the same eye, there are a set of parameters,

     eyeobj= commscope.eyediagram('SamplingFrequency', 10e9, ...
                             'SymbolsPerTrace', 2,...
                             'SamplesPerSymbol', 10, ...                       
                              'MinimumAmplitude', -1, ...
                              'MaximumAmplitude', 1, ...
                              'AmplitudeResolution', .001, ...
                              'MeasurementDelay', 0, ...
                              'PlotType', '2D Line', ...
                              'PlotTimeOffset', 0, ...
                              'RefreshPLot','on',...
                              'ColorScale', 'linear');
    eyeobj.update(data);

    Basically i am trying to convince that the eye diagram plot from matlab and cadence are one and the same. But what are the parameters that i have to additionally give to see the same eye diagram. I have given samples per symbol as 10, but in my earlier post, i have asked reg sampling frequency in cadence, you had told that there is no such thing (http://www.cadence.com/community/forums/T/23319.aspx). In that case what will be my Samples per Symbol ? I hope i am clear

    Currently with the given parameters, i am getting a matlab plot like this which is not the same as the cadence one, atleast in first look.

    http://www.4shared.com/photo/7uYbyIPm/matlabeye.html
     

     

     

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