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commsrc.pattern help

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I am having trouble using commsrc.pattern to generate the following psuedo-random binary signal:
Pattern: PRBS7
Bitrate: 28E9
Rise time: 10E-12
Fall time: 10E-12
Output Levels: [475E-3 725E-3]
PulseWidth = 35.71E-12 seconds (at 50% point)
I tried something like the following:
z = commsrc.pattern('SamplingFrequency',10*br,'SamplesPerSymbol',25,'PulseType','NRZ', 'OutputLevels', [-475E-3 725E-3], 'RiseTime', 10E-12, 'PulseDuration', 35.71E-12 , 'FallTime', 10E-12, 'DataPattern', 'PRBS7')
but it doesn't work. Any ideas?

Accepted Answer

Richard Allred
Richard Allred on 10 Jun 2021
Edited: Richard Allred on 14 Jun 2021
The property 'PulseDuration' is only valid when the 'PulseType' is 'RZ'. To solve your issue, simply don't specify the Pulse Duration property:
br = 28e9;
SamplesPerSymbol = 25;
z1 = commsrc.pattern(...
'SamplingFrequency',br,...
'SamplesPerSymbol',SamplesPerSymbol,...
'PulseType','NRZ', ...
'OutputLevels', [-475E-3 725E-3], ...
'RiseTime', 10E-12, ...
...'PulseDuration', 35.71E-12 , ...
'FallTime', 10E-12, ...
'DataPattern', 'PRBS7')
w1 = generate(z1,127);
figure(1),plot(w1)
An alternative solution is to use the stimulus object from the SerDes Toolbox
z2 = serdes.Stimulus(...
'SymbolTime',1/br,...
'SampleInterval',1/br/SamplesPerSymbol,...
'Modulation',2,...
'Order',7,...
'MapToVoltage',[-475E-3 725E-3]);
N = SamplesPerSymbol*127;
w2 = zeros(N,1);
for ii = 1:N
w2(ii) = step(z2);
end
figure(2),plot(w2)

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