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AD9361 DDS vs DAC output with complex tone

Question asked by tsh on Nov 4, 2016
Latest reply on Nov 11, 2016 by blue_ys

Hello,

 

We have been testing AD9361 using FMCOMMS3. We observed that the IQ tracking works well and the image component disappears. Using IIO-scope, a simple complex tone was transmitted in order to double check the IQ-tracking functionality.

Fs = 30.72 MHz

Ftone = 0.96 MHz (=Fs/32)

spectrum

 

Then, we did a loopback with following parameters with IIOscope:

TXatt: 10 dB

External attenuation: 20 dB (SMA-SMA attenuator)

IQ tracking: ON

DC tracking: ON (RF + BB)

Complex tone from DAC Buffer output or from DDS.

 

The DAC output seems to have many spurious tones compared to the DDS output:

comparison

 

How could we get as clean output with DAC output as with DDS?

Kind regards,

Timo Huusari

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