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:
- 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.
- 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?