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Define Modulation. Name and describe any three forms/methods of modulation with the help of diagrams.
Modulation
A process to convert digital signals into analog form is called modulation. Modulation is used because some data signals are not always suitable for direct transmission. The information can be transmitted through space as an electromagnetic wave. In modulation, data or message signals are combined with carrier waves or signals.
The basic modulation methods are as follows:
- Amplitude modulation
- Frequency modulation, and
- Phase modulation
1. Amplitude Modulation(AM)
It is a type of modulation where the amplitude of carrier waves varies in accordance with modulating signal. Amplitude Modulation modifies the amplitude of carrier to represent 1s or 0s. Binary digit “1” is represented by the presence of the carrier wave and “0” Absence of carrier wave. Amplitude modulation is used in the AM radio broadcast band.
2. Frequency Modulation(FM)
It is a type of modulation where the frequency of the carrier wave is varied in such a way that the change in frequency at any instance is proportional to another signal that varies with time. FM modifies the frequency of the carrier to represent the 1s or 0s. Binary digit “0” is represented by the original carrier frequency and “1” by a much higher frequency. FM is also commonly used for radio transmissions.
3. Phase Modulation
It is a type of modulation where the phase of the carrier wave varies in accordance with the modulating signal. This modulation is similar to frequency modulation. In FM, frequency of carrier wave varies, while in PM phase of the carrier wave changes. PM modifies the phase of the carrier to represent a 1 or 0.