commsrc.pattern help

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?

Answer 1

[Richard Allred]

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)