Amplitute Modulation
Amplitude modulation or AM is the process of varying the instantaneous amplitude of carrier signal accordingly with instantaneous amplitude of message signal.Thus, if m(t) is the message signal and c(t)=Acoswct then AM signal F(t) is written as
F(t)= Acoswct+m(t) coswct
F(t)=[A+m(t)] coswct
Frequency modulation
FM or Frequency modulation is the process of varying the in instantaneous frequency of Carrier signal accordingly with instantaneous amplitude of message signal. Thus, if m(t) is the message signal and c(t)=Acoswct then FM signal will beF(t)= Acos(wct+kf∫m(α)dα)
Pulse code modulationis a method that is used to convert an analog signal into a digital signal so that a modified analog signal can be transmitted through the digital communication network