The phenomenon of some of the higher frequencies in the spectrum of the signal g(t) appearing as lower frequencies in the spectrum of its sampled version is called

• The sampling theorem states that “a signal can be exactly reproduced if it is sampled at the rate fs which is greater than twice the maximum frequency W in the modulating signal."
• If the sampled frequency is less than the Nyquist frequency, overlapping of lower and upper sidebands known as aliasing takes place.
• The main reason for aliasing is undersampling \(i.e.\;{f_s} < 2{f_m}\)

           f_s = Sampling frequency and f_m = Modulating frequency

Aliasing is explained with the help of the spectrum as shown: