- The phenomenon of a high frequency spectrum of original signal x(t) taking on identity of lower frequency spectrum of sampled signal is called aliasing or fold over.

**Effects of aliasing**

Loss of some of information in original signal x(t).

**Preventive measures:**

- Use of antialising filter or pre-filter
- Using Nyquist criteria for sampling signal x(t),

f>2W , where W is maximum sampling frequency spectrum of original signal x (t).