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fmcomms1 i/q imbalance

Question asked by Stu_Adaptive on Oct 29, 2013
Latest reply on Nov 11, 2013 by DragosB

I have created a design where i set the ADC and DAC sample clocks to be the same and I take the ADC input and reclock it to the DAC clock and then output it directly to the DAC, essentially a "passthru" mode.  The goal is to show that I can take in an 802.11a signal at 2.4 GHz, downconvert to complex baseband and then send it back to 2.4 GHz through the TX path.  Eventually, I am going to add some processing at complex baseband.  What I have seen is I/Q imbalance and DC offset on the ADC side and then additional I/Q imbalance at the DAC output.  The ADC I/Q imbalance and dc offset can be taken care of with the current code and i can validate that it works by using chipscope.  Determining the DAC I/Q imbalance is a little more involved since I just see the RF output on a spectrum analyzer.  Any thoughts on the best way to analyze the I/Q imbalance out of the DAC?  I guess I need to pre-distort the output...???