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Frequency divider with NCO

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Charlie.za

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Hi at all

I have to descrived in vhdl a rate generator with a NCO.
I have a phase increment (2^32)*fo/fi (where fo is the frequency I want and fi is the core frequency), 0<fo<fi/2, and I take the output from the MSB of NCO.
With increments of 80000000h, 40000000h I get fo=fi/2, fi/4, etc., but what can I do with the others values (e.g. 70000000)? The output is not correct. :roll:
Thanks.

Regards.
 

what do you mean by "not correct".
I guess you saw some waveforms seemed to be not regular or complete as that in your mind.
That's fine.
That's how NCO works.
If you want to see a perfect sinusoid wave, you may use an analog lowpass filter to filter the output of NCO.
 

Yes. I've used an inappropriate sentence.
I've to generate a block for the code rate of a PRN sequence (CDMA demodulation for GPS channel receiver). Up to now, I known the frequency of the code and it was created by coreclk freq division (with NCO). But I didn't know the core frequency! This was the problem.
Today morning, I've discovered that the coreclk is multiple of code frequency.
However, the clock division by a no-integer value is a big problem.
Someone can help me for this task?

Thanks
 

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