Digital Drive

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RE: Chord up-samples?

Posted by yage on June 20, 2017 at 17:03:39:
Two points of clarification... probably more for me than for you.

You're right - there's no increase of encoded input signal bandwidth because that signal is already band limited to prevent aliasing at the ADC.

The interpolation filter should already be a low pass filter because of those reflected images at the original base sampling frequency (fs) that you mentioned. However, the low pass filter won't remove the image at the new, higher sampling frequency, L * fs, where L is the interpolation factor. That's the job of the reconstruction (or antialias) filter, which can now have a much simpler design because the images are now centered around L * fs.