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My input is a bpsk signal.
I didn't get the second question.
What do you mean by "but for bpsk signal I expect to see constellations of +/- on each I and Q"?
I was trying several things before I post this thread... and each one yields to different result... however when I open the loop they all give the same falling slope that I get in matlab if I open the loop. Let's try to eliminate options...
1- Do you recommend using Altera's NCO (First post in the thread) or go on with my DDS (previous post)?
2- I tried to use RRC after mixers instead of CIC... but CIC gave more closer results... what do you think about it? would it be a major cause to the problem?
3- I am scaling down the loop filter output that is used to subtract or add with NCO phi_inc. Am I right?
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Altera nco is ok. "my dds" is an nco if it works! there is no difference but possibly altera's one will have higher resolution (for phase).
To answer other questions follow this test:
ignore carrier tracking. Send bpsk signal from tx through rx with nco phase in both tx and rx at zero offset and see (after final RRC) that you get constellations by plotting:
plot(I_signal,'.');
you can do that in your model or sim by deactivationg the loop i.e. setting eror to zero at addition to nco word. (I don't use close/open as they can be confusing).
you should see +/- constellations on I axis. if it fails don't leave it to carrier tracking.
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