Digital Signal Processing Reference
In-Depth Information
1
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Figure 11.2
Downsampling by 2; the discrete-time signal's highest frequency is
π/
2 and no aliasing occurs.
Figure 11.3 shows an example in which the non-aliasing condition is vi-
olated. In this case,
2andthespectralcopiesdooverlap.
We can see that, as a consequence, the downsampled signal loses its low-
pass characteristics. Information is irretrievably lost and the original signal
cannot be reconstructed. We will see in the next Section the customary way
of dealing with this situation.
ω
=
2
π/
3
>π/
M
