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Changes to OQPSK Modulator objects after r2017

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I'm working with some old code that created an OQPSK signal with RRC pulse shaping and I'm trying to recreate some of its outputs. The signals originally produced by the code were using Matlab 2017a, and I'm currently using 2019a. The function signature for the OQPSKModulator object has changed between the two versions, but attempting to keep all things as equal as possible, the two versions create different constellations. The 2017 version also produces data twice as long as the 2019 version. What is the difference that is causing this?
Here is the 2017 code:
% 2017 Code
sps = 8;
hOQPSK = comm.OQPSKModulator('BitInput',true,'OutputDataType','single');
hTXFILT = comm.RaisedCosineTransmitFilter('FilterSpanInSymbols',10,'RolloffFactor',0.5,...
'OutputSamplesPerSymbol',sps,'Gain',sqrt(sps));
bits = randi([0,1], 1000, 1);
oqpsk = hOQPSK(bits);
oqpsk = hTXFILT(oqpsk)
and the 2019 code:
% 2019 Code
sps = 8;
hOQPSK = comm.OQPSKModulator('BitInput', 1, 'PulseShape','Root raised cosine','RolloffFactor',0.5,...
'FilterSpanInSymbols',10,'SamplesPerSymbol',sps);
bits = randi([0,1], 1000, 1);
oqpsk = hOQPSK(bits);

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Accepted Answer

Siriniharika Katukam
Siriniharika Katukam on 21 Feb 2020
Hi
One thing you have missed is to set the output datatype in 2019 code. The default is ‘double’ in 2019 but it is defined as single in 2017 code. The following link might be helpful:

  1 Comment

Abhinav Reddy
Abhinav Reddy on 24 Feb 2020
Thanks for the reply, using the solution from your link produced identical constellations

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