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Quadrature Tracking and RF DC Tracking

Question asked by look4terry on Apr 8, 2016
Latest reply on Aug 29, 2016 by look4terry

I have an application where we do manual gain control and we are switching frequencies often.  I have a problem that quadrature tracking and RF DC Tracking.  In my test case I use a CW signal.  Here are the two issue I see:

  1. When I leave the frequency constant and set the gain differently, I and Q will be different amplitudes.  The FFT will show a mirrored spur around the LO frequency.  The signal is a megahertz off the LO frequency.
  2. If I leave the gain setting constant but change the frequency (a long ways) the quadrature is bad and the DC Offset is large.  This is true even I call ad9361_do_calib( phu, RFDC_CAL, 0 );

Is there something else I should be doing?

 

Thanks,

Terry

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