Issue with commsrc.combinedjitter function

Mahesh Thorata

2018 10 20

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更新时间：2021 8 20

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Please refer to the code below. I set the Random Jitter value as 1e-12 and Deterministic jitter as [-2.5e-12 2.5e-12]. I generated 1e6 symbols and I ploted eyediagram with comm.EyeDiagram tool.

You can see that DJ value (highlighted with yello below) is coming as 5ps(peak to peak) and I am expecting RJ to be also 1ps. But it is coming as 14.36ps. BERThreshold is set as 1e-12.

Can you please let me know why I am seeing RJ as 14.36ps when I set the RJ as 1ps. Number of symbols generated are 1e6.

Fb = 25.78125e9; osr = 64;

src = commsrc.pattern( 'SamplingFrequency', Fb*osr,... 'SamplesPerSymbol', osr,... 'PulseType', 'NRZ',... 'OutputLevels', [-0.4 0.4],... 'DataPattern', 'PRBS7',...%); 'RiseTime',1e-12,'FallTime', 1e-12);

src.Jitter = commsrc.combinedjitter('DiracJitter', 'on', 'RandomJitter', 'on',... 'DiracDelta',[-2.5e-12 2.5e-12], 'RandomStd', 1e-12);

symbols = src.generate(1e6);

tx_out_ed = comm.EyeDiagram('Name', 'TX out Eye Diagram',... 'SampleRate',Fb*osr,... 'SamplesPerSymbol',osr,... 'DisplayMode','2D color histogram',... 'EnableMeasurements',true,... 'ShowBathtub','Both',... 'OverlayHistogram','Jitter', ... 'BERThreshold', 1e-12,... 'BathtubBER', [0.5 10.^-(1:15)],... 'ColorScale','Logarithmic', ... 'YLimits', [-0.45 0.45],... 'ShowGrid', true);

tx_out_ed(symbols);

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Mahesh Thorata 2018-10-22

I think I got the answer. RJ is calculated at BER 1e-12, which is 14 times more than the randomStd value that I entered in the combined jitter function. That is why I am seeing RJ as ~14.3ps.

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