Changes to OQPSK Modulator objects after r2017

Question

Abhinav Reddy 2020-2-13

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/505389-changes-to-oqpsk-modulator-objects-after-r2017

评论： Abhinav Reddy 2020-2-24

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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Answer 1

Siriniharika Katukam 2020-2-21

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/505389-changes-to-oqpsk-modulator-objects-after-r2017#answer_416648

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:

https://www.mathworks.com/matlabcentral/answers/99441-how-do-i-apply-the-raised-cosine-filter-to-an-oqpsk-signal-generated-by-the-oqpskmod-function-using