Amplitude Modulation (AM)

Amplitude Modulation (AM) is a type of modulation technique where the amplitude of a high-frequency carrier wave is varied in proportion to the amplitude of a low-frequency modulating signal. This results in a modulated signal that contains the original signal at a higher frequency.

The basic block diagram of an AM transmitter includes three main blocks: a modulating signal source, a high-frequency carrier wave source, and a modulator. The modulating signal source generates the low-frequency signal that is to be transmitted. The carrier wave source generates a high-frequency carrier signal that is typically several times the frequency of the modulating signal. The modulator combines the modulating signal with the carrier wave to produce the modulated signal.

Amplitude Modulation (AM)

The modulated signal can be expressed as:

s(t) = A_c [1 + m(t)] cos(2πf_c t)

where A_c is the amplitude of the carrier wave, m(t) is the modulating signal, and f_c is the frequency of the carrier wave. The term (1 + m(t)) is known as the modulation index, and it determines the degree of modulation.

At the receiver, the modulated signal is demodulated to extract the original low-frequency signal. The demodulation process typically involves the use of an envelope detector, which rectifies and filters the modulated signal to extract the original signal.

AM has several advantages, including simplicity and low cost. However, it also has several disadvantages, including susceptibility to noise and interference, low bandwidth efficiency, and limited frequency range. Despite these limitations, AM is still used in some applications, such as in commercial radio broadcasting.