What is an amplitude modulation?

A radio signal can carry information in the form of sound or image for broadcasting or communication. For it to be sent to a greater distance, the signal must be changed or modulated in some way. One of the easiest way is to change the amplitude of the signal with variations of the video or the audio signal. This is called Amplitude Modulaton. In this modulation information of message is carried in amplitude of carrier signal.

What is the principle of amplitude modulation (AM)?

The first signal of amplitude conversion was published in 1901 by a Canadian engineer named Reginald Fessenden. The engineer sparked a continuous transmission and placed a carbon microphone in the lead antenna. The sound waves affecting the microphones change their resistance and thus the transmission strength. The signals could be heard a few hundred feet away, though there was the sound of sparks. AM size or flexibility is one of the many variables used to transmit information over the radio. This method was developed in the 20th century when Landell de Moura and Reginald Fessenden conducted research using radiotelephone in the 1900s. After successful efforts, a flexible approach was developed and used for electronic communication.

Sound waves that affect microphones change their resistance, which in turn changes the transmission strength. Although it was very green, the signals could be heard a few hundred feet away, though there was the sound of rape caused by sparks. With the introduction of continuous sine wave signals, transmission improved significantly and soon became the standard for voice transmission. Today, with amplitude switching, AM is used for audio broadcasting in the medium and long frequency bands, as well as for two-way VHF radio transmission in aircraft. However, as there are now more efficient and simple ways to change the signal, its use is declining.

What is a modulation?

This process of putting in a signal into a carrier is called modulation. Put another way; changing the frequency of network operators to encrypt the data intended to manage is known as modulation. Flexibility is like hiding code in a wave of internet companies. The circuit used to generate AM is called a modulator. It has two inputs, a carrier and a model signal, and the output is a modified signal. The amplitude modulator includes the carrier product and the switching signal.

Modulation is the process in which carrier signal is varried accordance with the modulating(msg) signal.

Classification of modulation-

  • Analog modulation( amplitude modulation ,frequency modulation, phase modulation)
  • Digital modulation (pulse code modulation)

There are three types of analog modulation, namely:

  • Frequency modulation
  • Amplitude modulation
  • Phase modulation

Amplitude modulation

It is a kind of change in which the amplitude signal of the carrier is changed according to the message signal, while the phase and frequency remains unchanged.

The length (i.e., intensity or thickness) of the carrier wave changes to represent the data added to the signal.
Figure 1

Phase modulation

In this type of modulation, the phase of the carrier is adjusted according to the lower frequency signal of the message. The amplitude of the signal does not change while the frequency changes. Hence, it is called phase flexibility.

The waveform of the carrier will change with the change of the data frequency. In PM, the frequency does not change, but the phase changes relative to the carrier's frequency.

Frequency modulation

In this change, the frequency of the carrier signal is adjusted according to the message signal while maintaining the phase and amplitude. This is usually called frequency modulation.

The waveform frequency of the carrier changes to reflect the frequency of the data.
Figure 3

What is the process of amplitude modulation?

In the case of an analog signal, the carrier wave is modulated with respect to the message signal.

During modulation, one or more properties of the carrier wave are changed according to the message signal.

During amplitude modulation, the amplitude of the carrier wave is altered (decreased or increased but to its peak value only) according to the value of the message signal. Amplitude modulation is the process of transmitting wave signals by changing the size of the signal. It is commonly referred to as AM and is commonly used to transmit a piece of information through a radio transmitter. Amplitude modulation is widely used in the form of electronic communication.

Applications of amplitude modulation

In amplitude modulation (AM), the network signal amplitude varies according to the message signal. Amplitude change has many real-world applications. These are:

  • AM is used for long-wave or medium-wave broadcasting or short-wave bands. Very high frequency (VHF) transmission is processed by AM.
  • Radio communication uses VHF. A special type of AM is Quadrature Amplitude Modulation (QAM).
  • It is used to  transfer data from short distance transmission to mobile communications.
  • Broadcasting: AM is still widely used for long, medium and short-band broadcasts. It is easy to replicate, which means that a radio frequency receiver that can resolve amplitude modulate is cheap and easy to implement. However, many people are turning to higher quality transmission methods, such as frequency switching, FM or digital transmission.
  • Single Sideband: Amplitude switching in the form of single sideband is still used in high frequency radio links. With the efficient use of low frequency bandwidth and transmit power, this flexibility is still used at many points to identify high frequency links.
  • Quadrature Amplitude Switching: AM is widely used in data transmission in everything from short-distance wireless connections like wi-fi to mobile communications and much more. It is effectively built on two 90° carriers on the outside of the section.

Common Mistakes

Remember that, it is not efficient in terms of its use of bandwidth. It requires a bandwidth equal to twice that of the highest audio frequency.

Context and Applications

In each of the expert exams for undergraduate and graduate publications, this topic is huge and is mainly used for:

  • Bachelor of Technology in the Electrical and Electronic department
  • Bachelor of Science in Physics
  • Master of Science in Physics
  • Amplitude demodulation
  • Frequency modulation
  • Phase modulation

Practice Problems

Q1  In amplitude modulation, the instantaneous amplitude values ​​of a carrier change according to the amplitude variation and the signal frequency.

(a) True

(b) False

Correct option- (a)

Explanation- In amplitude modulation, the company's sine wave amplitude varies with the signal value of the network. The speed of the network carrier amplitude varies according to the amplitude and variation of the model signal frequency. The frequency of a carrier remains unchanged during the transition process, but its height varies depending on the model.

Q2 What is the line that connects the positive and negative peaks of a carrier format?

A) Peak line

B) Maximum amplitude ceiling

C) Modulation index

D) Envelope

Correct option- (d)

Explanation- An imaginary line connecting the positive and negative peaks of the carrier waveform gives the exact shape of the modulating information signal. This line is known as the envelope.

Q3 What is the reference signal module?

a) Zero Line

b) Carrier Peak Line

c) Modulated Peak Line

d) Un-Modulated Peak Line

Correct option- (b)

Explanation- The model signal uses a carrier value higher than zero as its reference area. The envelope changes up and down the amplitude of the top carrier. The zero reference line of the model signal corresponds to the maximum number of constant network companies.

Q4 What happens when the modular signal amplitude is greater than the carrier amplitude?

a) Decay

b) Distortion

c) Amplification

d) Attenuation

Correct option- (b)

Explanation- The zero reference line of the model signal corresponds to the maximum number of unchanging carriers. For this reason, the amplitudes associated with the carrier and the modular signal are important. When the amplitude of the measuring signal is greater than the amplitude of the carrier, distortion will occur.

Q5 What is the effect of distortion?

a) Total Information Loss

b) Error Information

c) Attenuated Information

d) Amplified Information

Correct option- (b)

Explanation- When the amplitude of the modulated signal is greater than the size of the carrier, distortion will occur, resulting in incorrect information transmission. In amplitude exchange, it is very important that the maximum

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