Principles of communication - IT 2202 Notes
The process of impressing low-frequency information signals onto a high frequency carrier signal is called Modulation.
Demodulation is the reverse process where the received signals are transformed back to their original form.
Amplitude modulation is the process of changing the amplitude of a relatively high frequency carrier signal in proportion with the instantaneous value of the modulating signal (information).Amplitude modulation is relatively inexpensive. It is used in two-way mobile communications.
Mathematical Equation of Amplitude modulation:
Em(t) = Emsinwmt ------> Em = amplitude of message signal
Ec(t) = Ecsinwct ------> Ec = carrier signal amplitude.
EAM(t) =Ec + Emsinwmt
EAM(t) = EAMsinwct
=Ecsinwct + maEcsinwct.sinwmt
Bandwidth ( B.W ) is calculated as Upper Cutoff frequency - Lower cut off frequency
= fc + fm – ( fc – fm)
B.W = 2 fm