Basic characteristic of RF transmission system is modulation. This is the technique in which the information is overlay on the radio carrier frequency. There are many techniques in which a radio carrier can be modulated to carry a given signal. The selection of modulation has a key decision in any radio communications system and has significant impact on the radio communications system because each having its own advantages and disadvantages.
Types Of Modulation
There are three main types of modulation, use for radio communications or RF signal:
- Amplitude modulation, AM
- Frequency modulation, FM
- Phase modulation, PM
Amplitude modulation, AM
This type of modulation involves the modulating the amplitude or strength of the signal. Amplitude modulation (AM) was the first type of modulation which was used to broadcast sound and other forms of Amplitude modulation.
Frequency modulation, FM
This type of modulation differ the frequency in line with the RF modulating signal. Frequency modulation has basic advantage that as amplitude variations do not carry any information in this signal. It is limited within the receiver unit to improve the signal strength and remove the variations and noise.
Phase modulation, PM
As the name states, Phase Modulation varies the phase of the carrier in line with the modulating signal. Frequency Modulation and Phase Modulation have several similarities. Both are differential of each other. Phase modulation gives itself to data transmissions.
Each type of modulation has its individual advantages and disadvantages. They are all used in different RF and radio communications applications. Some techniques are use for analogue applications and others for digital applications.