It was early in the 20th century the revolutionary communication tool, the AM waves were first broad casted. Canadian Engineer Reginald Fessenden and Landell de Moura found Amplitude Modulation (AM) technique. AM is a kind of modulation employed in the radio transmissions and broadcasting. Amplitude Modulation is the base of electronic communication and is used in transmitting information via the radio carrier waves.
Amplitude modulation is defined as a process in which the amplitude of the carrier wave is modified in accordance with some characteristic of the modulating signal. To be precise, it is the way in which the amplitude of the carrier wave is varied in proportion to that of the message signal being transmitted. The amplitude Modulation system is used in citizens band radio, VHF aircraft radio, portable two-way radios, and in QAM found in computer modems.
Amplitude modulation was discovered to mainly overcome the low signal-to-noise ratio and less accuracy transmission. A continuous sine wave generator first was introduced to improve the transmission quality. Later, Amplitude modulated waves became the standard for voice transmission.
Figure 1 shown below describes the modulating wave also known as message wave
Figure 2 explains the high-frequency signal – carrier wave
Figure 3 shown below explains the resultant modulated wave
It can be noted that the positive peaks and negative peaks of the carrier wave are integrated with an imaginary line to recreate the correct configuration of the modulating signal. This imaginary line on the carrier wave is referred to as an Envelope and is similar to the message signal.
Figure 1
Figure 2
Figure 3
The expression is given by:
Where,
- fc is the frequency of the carrier signal
- Ac is the amplitude of the carrier signal
- fm is the frequency of the modulating signal
- Am is the amplitude of the modulating signal
AMP Modulation is used in :
- Air band radio
- Broadcast transmissions
- Single sideband
- Quadrature amplitude modulation
Advantages of using AM are:
- Easy to implement
- It can be easily demodulated using less circuit components
- AM receivers are affordable
- The set up does not demand any specialized components
Disadvantages of using AM are:
- Not effective since it consumes more power
- Signals are exposed to high levels of noise
- It is not efficient in terms of bandwidth
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