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AD9125 internal NCO

Question asked by JulianoCioffi on Nov 17, 2015
Latest reply on Mar 7, 2016 by MicheleV

Hello I have a development running inside a design house and I have been asked for this support:

 

They are trying to use the internal NCO from the DAC to shift the frequency of the input sine wave.

 

With that  it would be possible inject a sine to 7.8125Mhz in DAC(32 samples with the interface / NCO of the FPGA to 250Mhz), to have more samples per full wave, and increase its output frequency with the internal DAC NCO.

 

However, they can only configure the internal NCO with the same frequency of the input coming from the FPGA. If they generate a sine with the DAC NCO in another frequency will come out a wave composed with another .. Is there any setting possible to make the NCO to "fit" the signals or can only double the frequency of the input through it?

 

I attached a print to illustrate the "wave composed with another"

 

mixed.jpg

 

In this case, the first sine is 62.5Mhz via an NCO running at 250Mhz in the FPGA (4 samples) and adding 31.25Mhz with a sine generated by the internal DAC NCO running at 500Mhz ..

 

The pure sine (without use of the DAC NCO) with 4 samples coming from the FPGA and 4x interp IN DAC(16 samples).

 

pure.jpg

Thanks a lot and have a great week!

 

Att,

 

Juliano K. Cioffi - FAE 

Latinrep South America - Analog Devices

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