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Distorted signal and DC offset on receiver FMCOMMS1

Question asked by mmauri on Aug 1, 2013
Latest reply on Nov 11, 2013 by DragosB

I got the FMCOMMS1 development kit working with the ML605 board. I get a nice sine wave display on  ChipScope connected to the output of the ADC pcore. However, when I attempt to lower the amplitude of the DAC pcore DDS generated sine wave to anything below full range, I get distortion and dc offset on the ADC output. The output is not predictable, if I power cycle the board the waveform and DC offset changes to different value and shape.

 

I am only changing the amplitude of the DDS. I  verified that the DDS is outputing the correct amplitude using ChipScope connected to the DAC DDS output..

 

What is causing the distortion and DC offset when the amplitude is lowered?

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