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Altera_Forum
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11 years ago

Costas Loop oscillates in ModelSim while locks in MATLAB!

Hello again, I have designed a Costas Loop in MATLAB and it simulates very well... locking and recovering the carrier. Here are the results: http://www.alteraforum.com/forum/attachment.php?...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
11 years ago

when doing above test in modelsim make sure the phase of tx nco is same as that of rx nco. If not adjust rx nco to match when they get together. Both sine and cosine waves mustmatch in phase at rx mixer(sine will be inverted for negative frequency)

Regarding rrc/cic I don't know about your chain but normally RRC is first in tx, last in Rx.