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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