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"
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).
Thanks a lot and have a great week!
Juliano K. Cioffi - FAE
Latinrep South America - Analog Devices
At what sampling rate are you running the AD9125 DAC?
What is the frequency of the AD9125 output signal you want to generate and is it a tone?
Use of the NCO requires use of an I/Q pair of signals. The sampling rate of the FPGA is the DAC sampling rate divided by the interpolation factor.