AD6676 Internal Signal Processing Chain Related

Inquiry about the scaling factor used within the signal processing chain within the AD6676.

The data is available at the baseband output as shown in the figure (left one) but the GUI enabled with AD6676 evaluation board plots the spectrum in the bandpass frequency region which is shown in the figure below (right one).

So is it that the GUI internally, does up sampling and modulation on the obtained baseband I and Q data and runs an FFT at the (sort of reconstructed) passband data. If so is there any scaling factor used within just to keep the Pin and Pout same?

Can someone please throw light on how the GUI is able to plot FFT reflecting the passband frequency region when the data obtained is the baseband I and Q data.

  • 0
    •  Analog Employees 
    on Apr 8, 2021 1:55 PM

    Hello,

    The GUI display (by default)  normalizes the FFT display to the IF center by simply shifting baseband IQ frequency spectrum to be centered about the IF (i.e. simple shift in graphs Frequency axis).   This make it easier when observing the RF input signal frequency so that tone observed on FFT display matches what the RF signal generator is set too.   That said.................I believe an option also exists on GUI front  panel settings that allows displays data in its native baseband zero-IF format. 

  • Thank you for the reply. It still remains unclear to me, since to do the frequency translation, you would have to modulate the baseband signal. Is it not? 

    We could not find the GUI front panel setting option that allows spectrum plot in its native baseband format.