Difference between Frequency Modulation and Phase Modulation

Prerequisite – Modulation

1. Frequency Modulation :
Frequency Modulation is a modulation in which the frequency of the carrier wave changes according to the instantaneous amplitude of the modulating signal keeping phase and amplitude constant. The frequency of the carrier wave is modified in order to send the data or information. It cannot transmit over long distances, have a smaller range. Its modulation index is always greater than one. In Frequency Modulation amplitude and phase remain the same.

2. Phase Modulation :
Phase Modulation is a modulation in which the phase of the carrier wave changes according to the instantaneous amplitude of the modulating signal keeping amplitude and frequency constant. Phase Modulation and Frequency Modulation are similar, but in Phase Modulation frequency of the carrier signal is not increased. Phase Modulation is used in mobile system. The phase of the carrier wave is modified in order to send the data or information.


Difference between Frequency Modulation and Phase Modulation :

S.NO. Frequency Modulation Phase Modulation
1. In Frequency Modulation amplitude and phase remain the same. In Phase Modulation, the frequency and amplitude remain the same. 
2. Frequency Modulation is proportional to modulating voltage. Phase Modulation is proportional to modulating voltage.
3. Associated with the change in frequency, there is some phase change. Associated with the change in phase, there is some frequency change.
4. It is possible to receive FM on a PM receiver. It is possible to receive PM on a FM receiver.
5. Noise immunity is poor than AM and PM. Noise immunity is better than AM but worst than PM.
6. Signal to noise ratio is better than in phase modulation. Signal to noise ratio is poor than in frequency modulation.
7. Frequency Modulation is widely used. Phase Modulation is used in mobile system.
8. In FM, the frequency derivation is proportional to the modulating voltage only. In PM, the frequency derivation is proportional to the modulating voltage as well as modulating frequency.
9. Amplitude of FM wave is constant. Amplitude of PM wave is also constant.
10. In FM, received signal is of high quality. In PM, received signal is of low quality.

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