Honored Contributor
Honored ContributorThis is greatly useful to know although it's simple... I believe you've just vanished another confusion I had regarding Costas Loop in general!
I have had the question of why does it change the nco word, based on your note the nco word should change for a little of time and come back... that means it should oscillate because I don't expect it to come back instantly! So my design might be correct! From another point of view... this is different from matlab simulation... because the loop output in matlab keeps steady after lock on a constant and doesn't come back to the initial value. And this is correct I think because in matlab I am controlling PHASE of the cosine function which happens to be separate from frequency in a way or another, and this is not the case in Modelsim and NCO where there is only one thing (NCO word) that determines freq and phase. I don't know if you got my point regarding the comparison between matlab and modelsim... but am I right?
