8 December 2019

Comparison Between Frequency Modulation ( FM ) and Amplitude Modulation ( AM )


Amplitude Modulation
  • When the amplitude of the carrier wave is changed according to intensity of signal, it is called as amplitude modulation.
  • Amplitude of carrier wave changes with modulation
  • Carrier frequency remain constant with modulation
  • The amplitude of signal changes according to strength of modulating signal.
  • The modulation index is always less than unity for AM signal
  • Modulation index in AM : it is defined as the ratio of amplitude of change of carrier and amplitude of normal carrier.

        Modulation index = Signal Amplitude / Carrier amplitude
Frequency Modulation
  • When the frequency of the carrier wave changed according to intensity of signal, it is called as frequency modulation.
  • Carrier frequency changes with modulation
  • The carrier frequency changes with respect to strength of modulating signal.
  • The value of modulating index is always less than unity.
  • Modulation index in FM : It is defined as ratio of maximum frequency deviation and frequency of modulating signal.
      Modulation index = Maximum frequency deviation /                                                                       Modulating  frequency
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