DESP2045 / week 4

Aliasing in practice

Aliasing is easy to demonstrate and hard to notice. A sampled sine at f_s/2 + Δ is indistinguishable from one at f_s/2 − Δ, so the measured frequency moves in the opposite direction from the true one.

Two practical consequences: an anti-aliasing filter must be analog and must sit before the converter, and a digital filter placed afterwards cannot undo the fold — it can only hide it.

Laboratory connection

In Laboratory 2 the sample rate is varied while the input frequency stays fixed. Record the observed frequency, not the expected one; the difference is the point of the exercise.