Fixed point arithmetic not working for digital signal processing application

Thank you for your documents. I will keep them at hand.

The size of my signals do not seem to be the problem though. I have followed the guidelines that are outlined in the .pdf and I still get the same result for my output.

Moreover, the output waveform does not look like a sine with a horizontal "cut" at some height (notice that the cut seems asymmetric). This suggests to me that there is somethign else than a bit-width problem.