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What is AM Modulation (Amplitude Modulation)? – Need of Modulation

Detailed Explanation of  AM Modulation (Amplitude Modulation), its working principle, and basic Need of Modulation.

Communication is a process of conveying information at a distance. If the distance is involved is beyond direct communication, electronic communication comes into the picture. One of the principal techniques used in an electronic communication is the modulation.

Modulation Definition:

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Modulation is the process of having the information signal to be transmitted alters a higher-frequency signal for the purpose of transmitting the information somewhere at a higher distance.

In electronic communication we usually study three types of modulation techniques:

  • AM Modulation (Amplitude Modulation)
  • FM Modulation (Frequency Modulation)
  • PM Modulation (Phase Modulation)

The oldest and simplest method is AM Modulation Also known as Amplitude Modulation. And in this article, we will learn about Amplitude Modulation Step by Step. 

What is AM?

AM Modulation (Amplitude Modulation) is the technique in which the Amplitude of Carrier wave varies with the variation in the frequency and amplitude of Information Signal.

Few points to Remember:

  • A carrier wave is High-Frequency, Sinusoidal Signal which has a greater frequency compared to the Information Signal.
  • An Information signal may be audio, video signal which is sinusoidal in nature and it is also referred to as Baseband signal or Modulating Signal.

The concept of AM Modulation (Amplitude Modulation):

In order to transfer information signal at the higher distance, we use Modulation technique and one of the best modulation technique is AM Modulation (Amplitude Modulation) Technique. “In AM Modulation, the carrier wave amplitude changes in accordance with the amplitude and frequency variations of the information signal”.

Give figure below shows the information signal modulating a high-frequency carrier wave. In the modulation process, the carrier’s frequency remains constant only its amplitude varies with the variation of the information signal.

An increase in the amplitude of information signal can cause the increase in the carrier amplitude. Both positive and negative peaks of carrier wave vary with the variation of amplitude of information signal. An imaginary line connecting the positive peaks and negative peaks of the carrier waveform gives the exact shape of the information signal. This imaginary line on the carrier waveform is known as the envelope.

caption id=”attachment_1443″ align=”aligncenter” width=”602″]Amplitude Modulation AM modulation (Amplitude Modulation)[/caption]

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This envelope contains the real information of information signal as it has the exact shape as an information signal. And in order to maintain the real information in the envelope.

The amplitude of the modulating signal should be less than the amplitude of the carrier. When the amplitude of the modulating signal is greater than the amplitude of the carrier, distortion will occur, causing incorrect information to be transmitted.

υm < υc

  • Here Vm is modulating Signal voltage also known as Information Signal voltage:
  • Vc is Carrier voltage.

υm= Vmsin(2πfmt)

  • where υm is the instantaneous value of information sine signal
  • Vm = peak amplitude of information sine signal
  • fm = frequency of modulating sine signal

υc= Vc sin(2πfct)

  • where υc is the instantaneous value of carrier sine signal
  • Vc = peak amplitude of carrier sine signal
  • fc = frequency of carrier sine signal

Using this value of carrier wave voltage and information wave voltage we can calculate the overall modulated wave.

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An envelope is consisting of the information signal in his top and bottom, in order to find out the envelope voltage either for the top or the bottom we can use the equation.

υ1= Vc+ υm= Vc+Vm(sin2πfmt)

Thus, we can write the instantaneous value of the complete modulated wave υ2 by substituting υ1 for the peak value of carrier voltage Vc as follows:


Now substituting the previously derived expression for v1 and expanding, we get the following:

υ2=(Vc +Vm(sin2πfmt))*sin(2πfct)

= Vc (sin2πfct)+ (Vmsin2πfmt)*(sin 2πfct)

where υ2 is the instantaneous value of the AM wave, Vcsin2πfct is the carrier waveform, and (Vm (sin2πfmt))(sin 2πfct) is the carrier waveform multiplied by the information signal waveform.

It is the second part of the expression that is characteristic of AM Modulation.

A circuit must be able to produce a mathematical multiplication of the carrier and modulating signals in order for AM to occur. The AM wave is the product of the carrier and modulating signals.

AM Modulator

AM Modulator

The circuit used for producing AM is called a modulator. Amplitude modulators perform the product of the carrier and modulating signals.

Generation of an AM wave can be accomplished simply by using a nonlinear device (e.g., diode) in a square-law modulator.

Need for modulation:

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Modulation is needed in a communication system to achieve the following basic needs

  • Multiplexing (Process of transmitting two or more signals simultaneously over a channel)
  • Reduction of antennas Size. (We will cover this in our upcoming articles)
  • Narrow banding (Using modulation technique the bandwidth is reduced we can transmit our information with the less wasting of bandwidth).

Advantages of AM Modulation (Amplitude modulation):-

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  • Generation and detection of AM signals are very easy
  • It is very cheap to build, due to this reason it is most commonly used in AM radio broadcasting.

Disadvantages of AM Modulation (Amplitude modulation):-

  • Amplitude modulation is wasteful of power: The upper and lower sidebands of an envelope are same hence they utilize the amount of power in the Amplitude Modulation.
  • Amplitude modulation is wasteful of bandwidth: The upper and lower sidebands of an AM wave are identical hence they have the same information. This means for the transmission of information only one sideband is necessary. In light of this observation, amplitude modulation is wasteful of channel bandwidth as it requires a transmission bandwidth equal to twice the message bandwidth.

In order to overcome these two limitations of AM Modulation (Amplitude Modulation), we make some sort of modifications in AM Modulation.

These modifications in AM Modulation are known as:

  • Double Side Band Suppressed Carrier (DSB-SC):
  • Single Side Band Suppressed Carrier (SSB-SC):
  • Single Side Band (SSB)
  • Vestigial Sideband (VSB)

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All of these Amplitude Modulation techniques are covered, Click here

Application of AM Modulation (Amplitude modulation):-

  • AM Radio Broadcasting

Also, Read our Article:

  1. Introduction to Electronic Communication.
  2. Types of Electronic Communication (Simplex, Duplex, and Half Duplex).
  3. Practical Applications of Simplex and Duplex Communication.
  4. Modulation Index, | Depth of Modulation | Percentage Modulation
  5. What is Sideband? Single Sideband Modulation, DSB-SC, and Vestigial Sideband
  6. Difference Between TDM and FDM
  7. Greek Alphabet Letters and Symbol

If you like our article on Modulation Definition- What is AM Modulation (Amplitude Modulation)? – The need of Modulation then do not forget to rate our article, and also do not forget to comment below on this article. Thanks for your visit keep connected for the great information.

Types of Electronic Communication (Simplex, Duplex and Half Duplex)

Communication means exchanging information from one place to another, it is what Human beings do to convey their emotions, their thoughtsideas and feelings to one another. Communication is happening from the beginning of humankind. Most Humans communicated through spoken words or with their gestures and postures (Nonverbal communication). Later written communication was developed. Humans wrote letters to one another and eventually invented newspapers and books. Although the bulk of huge information is still oral, a huge volume of information is exchanged by means of the written word.
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In this article, we will cover all different types of Electronic Communication and their uses, we will also cover the basic terminologies related to Electronic communication.

Types of Electronic Communication:

Electronic Communication is classified into three different ways:

  1. One-way and Two-Way Communication:
  2. Analog and Digital Communication:
  3. Baseband and Modulated Signal:

In this article we will cover these all three different ways of electronic communication step by step:

One-Way Communication:

One-way communication or simplex communication is the simplest form of communication. In Simplex communication information travels only in one direction.

Simplex communication

the flow of Simplex communication

A common Example of One-way or Simplex Communication is TV Broadcasting, RADIO, and Music. In these all types of Electronic communication, information travels from source to destination through one-way only.

Two-Way Communication:

The rest of electronic communication in the world is almost two-way communication. Two-Way Communication is further classified into two different ways.

  1. Half Duplex
  2. Full Duplex

For Example: When an individual person communicates with one another over the telephone, each can transmit and hear information simultaneously, such two-way communication is referred to as Full Duplex Communication.

Full duplex communication

Full Duplex Communication

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Few Common Example of Full Duplex Communication is Telephone, Two-way radio, Radar, and Sonar etc… Another form of two-way communications is where only one person can transmit or receive information at a time, this type of communication is known as Half Duplex.

Half Duplex Communication

Half Duplex Communication

A common Example of Half Duplex Communication is walkie-talkies, amateur radio.

type of Electronic communication

type of Electronic communication

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Analog Communication:

Another way of categorizing electronic communication is by the type of information signal. There are two types of the information signals  Analog, and Digital signals. An Analog Signal which contains information is a continuously varying voltage or current. All the signals in nature are analog in form. A voice signal is an analog signal.

Analog communication

Analog communication

A typical information signal in analog form is voice signal which is basically a sine wave, video signals are also analog signals.

Digital Communication:

The other type of communication is Digital Communication. Almost most of the electronic communication in nowadays is in the form of digital communication. Digital communication uses a type of codes which represent ON/OFF condition.

Digital Communication

Digital Communication

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Data used in computers is also digital in nature where binary codes represent numbers, letters, and symbols. The most commonly used digital code in electronic communication is the American Standard Code for Information Interchange (ASCII).

Baseband Signals:                                                                                        

An Information signal whether it is in analog form or in digital form is known as a baseband signal. In communication systems, there are two ways of transmitting an information signal to the destination. One is when the information signal is directly transmitted over the medium and another way and efficient way is to modulate the information signal with the high-frequency wave and then sending it for transmission over the medium.

If a voice, video or digital signal are transmitted directly into the medium then it is referred to as baseband transmission or communication.

For example: in computer communication, the digital signals are directly transmitted through the wire to the destination.

Another good example of baseband communication is very interesting, just take a cup to connect that cup with a wire and at the end of wire connect another cup. Now when you will generate voice signal it will be your voice that will directly flow through the medium to another cup. 😀

 baseband communication

baseband communication


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Another way of transmitting information signal through the medium to the destination is use of modulation technique. There are many instants when the simple baseband transmission is not compatible for example we cannot transmit a voice signal directly to radio. To transmit baseband signal by radio we need modulation technique. The techniques using modulation are referred to as broadband.



In modulation technique the baseband signal is superimposed with the higher frequency wave (carrier) this carrier signal have a much higher frequency than the baseband signal and this carrier signal varies with the variation of baseband signal hence the higher distance communication can be achieved using this modulation technique.

This is a very useful technique in electronic communication and we will further study this technique in detail in our upcoming articles.

There is three basic type of modulation techniques:

  1. AM Modulation or Amplitude Modulation
  2. FM Modulation or Frequency Modulation
  3. PM Modulation or Phase Modulation

In AM Modulation the amplitude of the modulating signal varies with the variation of baseband signals amplitude and phase.

In FM modulation the frequency of the modulating signal varies with the variation of baseband signals amplitude and phase.

In PM modulation the phase of modulation signal varies with the variation of baseband signals amplitude and phase.

Source of gif images: IEC
Also Read:
  1. Introduction to Electronic Communication
  2. Practical Applications of Simplex and Duplex Communication
  3. What is AM Modulation? – Need of Modulation
  4. Modulation Index, | Depth of Modulation | Percentage Modulation
  5. What is Sideband? Single Sideband Modulation, DSB-SC, and Vestigial Sideband
  6. Difference Between TDM and FDM
  7. Greek Alphabet Letters and Symbol

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