Amplitude modulation notes | Principles of communication IT 2202 Unit 1 - Fundamentals of analog communication | Modulation | Demodulation | Amplitude modulation & its mathematical equation | Bandwidth

Principles of communication - IT 2202 Notes

Amplitude Modulation

Modulation:

The process of impressing low-frequency information signals onto a high frequency carrier signal is called Modulation.

Demodulation:

Demodulation is the reverse process where the received signals are transformed back to their original form.

Amplitude Modulation:

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:

                                        

                                          E_m(t) = E_msinw_mt   ------>  E_m = amplitude of message signal

                                          E_c(t) = E_csinw_ct    ------>  E_c = carrier signal amplitude.

                                                 E_AM(t) =E_c  +  E_msinw_mt

E_AM(t) = E_AMsinw_ct

                = E_c(1+m_asinw_mt)sinw_ct

                =E_csinw_ct  + m_aE_csinw_ct.sinw_mt

                                                            

 

Bandwidth:

Bandwidth ( B.W ) is calculated as Upper Cutoff frequency  - Lower cut off frequency

                                                = f_c + f_m – ( f_c – f_m)

                                B.W        = 2 f_m