Amplitude modulation (AM) is a modulation technique used in communication systems to transmit information over a carrier wave by varying its amplitude.

The process of modulating the carrier wave with the information signal is known as modulation, and the resulting waveform is called the modulated signal.

The derivation of amplitude modulation involves combining the carrier wave and the information signal using a nonlinear device called a modulator. The modulator multiplies the carrier wave with the information signal, producing a modulated signal that varies in amplitude with the information signal.

What is Amplitude Modulation

Amplitude Modulation (AM) is a method of transmitting information over a radio wave by varying the amplitude (or strength) of the carrier wave to reflect the changes in the amplitude of the original signal.

In AM, the carrier wave’s frequency remains constant, while the amplitude changes in response to the modulating signal.

Derivation of Amplitude Modulation

Amplitude Modulation (AM) is a modulation technique used in communication systems to transmit information over a carrier wave by varying the amplitude of the wave. Here is a derivation of AM-

m(t) = A_mcos (2f_mt) (modulating signal)

c(t) = A_ccos (2f_ct) (carrier signal)

s(t) = (A_c+ A_mcos (2f_mt)) cos(2f_ct)

Where,

A_m = Amplitude of Modulating signal

A_c = Amplitude of Carrier signal

Modulation Index Derivation

Modulation index is a term used in the context of modulation techniques. It is a measure of the degree to which a carrier signal is modulated by a modulating signal.

= A_m / A_c

Let the maximum and minimum amplitude of the wave are A_max and A_min

A_max = A_c + A_m

A_min = A_c – A_m

A_max + A_min = A_c + A_m + A_c – A_m = 2 A_c

A_c = (A_max + A_min) / 2

A_max – A_min = A_c + A_m – A_c + A_m = 2 A_m

A_m = (A_max – A_min) / 2

= A_m / A_c

This is the derivation of modulation index.

Types of Amplitude Modulation

Amplitude modulation (AM) is a type of modulation in which the amplitude of a carrier wave is varied in proportion to the amplitude of a modulating signal. There are several types of amplitude modulation, including-

Double Sideband (DSB) AM: In this type of AM, both the upper and lower sidebands are transmitted. The carrier wave is suppressed, and only the sidebands are transmitted. DSB is commonly used in radio broadcasting.

Single Sideband (SSB) AM: This type of AM suppresses one of the sidebands and the carrier wave, leaving only one sideband for transmission. SSB is more efficient than DSB because it uses less bandwidth.

Vestigial Sideband (VSB) AM: This type of AM transmits both sidebands but partially suppresses one of the sidebands. VSB is used in television broadcasting to reduce the bandwidth required for transmission.

Advantage and Disadvantage of Amplitude Modulation

AM involves varying the amplitude of a high-frequency carrier wave to carry information. AM has several advantages, it also has some disadvantages, which are discussed as-

Advantages of Amplitude Modulation

Simplicity: AM is a simple modulation technique that requires only a few basic components, making it easy and inexpensive to implement.

Compatibility: AM signals can be easily demodulated using a simple detector circuit, making it compatible with a wide range of receivers.

Disadvantages of Amplitude Modulation-

Susceptible to noise: One of the primary disadvantages of AM is its susceptibility to noise. The amplitude of the signal can be affected by external noise sources, resulting in a degraded signal quality.

Limited bandwidth: AM has a limited bandwidth, which restricts the amount of information that can be transmitted.

Interference: Another disadvantage of AM is that it is susceptible to interference from other radio signals, which can result in poor signal quality.