When digitally mixing an IF down to baseband, one is left with a spectrum that consists of the baseband (Fif - Fmix = 0Hz) and an image (Fif + Fmix). If the IF is greater than the Nyquist freq, the image will wrap back into the first Nyquist zone (0 to Fn).
Normally the next step in demodulation is decimation, which consists of lowpass filtering out the image (often with CICs) and then dropping some of the resultant samples to get a lower sample rate.
Is there a method by which an image-reject mixer could mix the IF down to baseband while simultaneously cancelling the image? If so, it seems like there would be no filtering required for decimation, which would consist entirely of throwing samples out. Then it also seems that the mixer itself could run at the slower decimated rate.
Or is that all just another way of saying "undersampling"?