Classification of Modulation Techniques : A Complete Guide (Analog Modulation and Digital Modulation)

Classification of Modulation Techniques

Modulation is an essential part of modern communication systems. It allows us to transmit information over long distances using electromagnetic waves. Without modulation, technologies like radio, television, and the internet would not exist. This article explores the classification of modulation techniques in a simple and easy-to-understand way.

What is Modulation?

Before diving into classifications, let’s understand modulation. Modulation is the process of changing one or more properties of a carrier signal (like amplitude, frequency, or phase) based on the information signal.

A carrier signal is a high-frequency wave used to carry the actual message. The information signal is the message we want to transmit. Modulation helps make the message suitable for transmission and reduces signal loss.

Classification of Modulation Techniques

Modulation techniques are broadly classified into two categories:

1. Analog Modulation
2. Digital Modulation

Let’s break these down further.

1. Analog Modulation

Analog modulation is used when the information signal is analog, like audio or video signals. It modifies a continuous carrier wave to transmit the message.

Analog modulation has three main types:

a. Amplitude Modulation (AM):
In AM, the amplitude of the carrier wave changes based on the information signal. The frequency and phase remain constant.

• Example: AM radio broadcasting.
• Advantage: Simple and inexpensive.
• Disadvantage: Sensitive to noise.

b. Frequency Modulation (FM):
In FM, the frequency of the carrier wave varies according to the information signal. The amplitude and phase stay unchanged.

• Example: FM radio stations.
• Advantage: Better sound quality and resistance to noise.
• Disadvantage: Requires more bandwidth than AM.

c. Phase Modulation (PM):
In PM, the phase of the carrier wave changes with the information signal. Amplitude and frequency remain constant.

• Example: Certain communication systems like Wi-Fi.
• Advantage: Provides high data transmission rates.
• Disadvantage: Complex implementation.

2. Digital Modulation

Digital modulation is used when the information signal is digital, like binary data (0s and 1s). It modifies the carrier wave to transmit digital information.

Digital modulation has several types, including:

a. Amplitude Shift Keying (ASK):
In ASK, the amplitude of the carrier wave is switched between two levels: one for binary 1 and another for binary 0.

• Example: Low-speed digital communication.
• Advantage: Simple and cost-effective.
• Disadvantage: Highly affected by noise.

b. Frequency Shift Keying (FSK):
In FSK, the frequency of the carrier wave alternates between two values based on the binary data.

• Example: Radio-frequency identification (RFID).
• Advantage: More robust to noise than ASK.
• Disadvantage: Needs more bandwidth.

c. Phase Shift Keying (PSK):
In PSK, the phase of the carrier wave shifts to represent binary data.

• Example: Satellite communication.
• Advantage: Efficient use of bandwidth.
• Disadvantage: Requires precise synchronization.

d. Quadrature Amplitude Modulation (QAM):
QAM combines ASK and PSK. Both amplitude and phase of the carrier wave are modified.

• Example: Cable television and modems.
• Advantage: High data rates.
• Disadvantage: Susceptible to noise.

Comparison of Analog and Digital Modulation Techniques

1. Signal Type

   • Analog Modulation: Works with continuous signals like audio or video.
   • Digital Modulation: Works with discrete binary signals (0s and 1s).

2. Noise Resistance

   • Analog Modulation: Less resistant to noise, leading to signal degradation.
   • Digital Modulation: Highly resistant to noise, ensuring better signal quality.

3. Bandwidth Efficiency

   • Analog Modulation: Moderate bandwidth efficiency.
   • Digital Modulation: More efficient use of bandwidth.

4. Complexity

   • Analog Modulation: Simpler to implement and less costly.
   • Digital Modulation: More complex and expensive.

5. Data Transmission

   • Analog Modulation: Suitable for continuous data like sound or video.
   • Digital Modulation: Ideal for data-intensive communication, like internet and multimedia.

6. Signal Quality

   • Analog Modulation: Quality decreases with distance and interference.
   • Digital Modulation: Maintains quality over longer distances.

7. Error Detection and Correction

   • Analog Modulation: Does not support error correction.
   • Digital Modulation: Allows error detection and correction for reliable communication.

8. Applications

   • Analog Modulation: Used in AM/FM radios, analog TV, and basic telephony.
   • Digital Modulation: Used in mobile networks, Wi-Fi, digital TV, and satellite communication.

9. Hardware Requirements

   • Analog Modulation: Requires simpler hardware for modulation and demodulation.
   • Digital Modulation: Needs advanced hardware for processing.

10. Scalability

• Analog Modulation: Less scalable due to limited bandwidth.
• Digital Modulation: Highly scalable, suitable for modern high-speed networks.

Choosing the Right Modulation Technique

The choice of modulation technique depends on:

• The type of signal (analog or digital).
• Distance of transmission.
• Noise levels in the environment.
• Bandwidth availability.
• Complexity and cost of the system.

For example:

• AM and FM are perfect for broadcasting audio over long distances.
• QAM is ideal for high-speed data transfer.

Conclusion

Modulation is the heart of communication systems. Analog modulation is best for continuous signals, while digital modulation is essential for modern data-driven systems. Each modulation technique has its strengths and weaknesses, and choosing the right one depends on the application.

Understanding modulation techniques helps us appreciate the technology that powers everything from radios to smartphones. It’s a fascinating field that continues to evolve as communication needs grow.

Ring Modulator Explained with Simulation - Generation of DSB SC

Here we will understand what is a Ring Modulator along with Where and Why the Ring Modulator is used? The structure and working of the ring modulator has been explained here with the help of beautiful circuit simulation software (Falstad Circuit Simulator). 

What is Ring Modulator (Ring Modulation)

A Ring modulator is an electronic device that is used for ring modulation.

Ring modulation is the implementation of frequency mixing. It is performed by multiplying two signals. One signal is a simple waveform (typically a sine wave) and another signal is the signal that we want to modulate.

Where and Why Ring Modulator is used

Ring modulator can be used to generate double sideband suppressed carrier (DSB SC) wave. DSB SC is a type of amplitude modulation where in the modulated wave contains only two side bands and the carrier wave is suppressed.

Why it is called Ring Modulator

The ring modulator circuit  implements diodes in clockwise or anticlockwise arrangement. Hence it takes the shape of a ring. That's why it is called as the ring modulator.

Ring Modulator Applications

A ring modulator finds applications in music synthesizer or as an effects unit.
The ring modulator heterodynes (frequency mix) two waveforms. The output is the sum and difference of the frequencies that are present in each waveform.

Ring Modulator Simulation (Generation of DSB SC)

Attributes: https://www.falstad.com/circuit/

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Generation of Binary Phase Shift Keying (BPSK Generation) - Block Diagram of Binary Phase Shift Keying (BPSK)

Here we will understand the generation of BPSK signal. BPSK stands for Binary Phase Shift Keying. With the help of block diagram we will discuss the concept of Binary Phase Shift Keying generation.
But before discussing the generation of Binary Phase Shift Keying, we will first understand what is Phase Shift Keying (PSK).

Watch the Complete Video Here-

Phase Shift Keying (PSK) Introduction

In Phase Shift Keying, the phase of the carrier wave (analog) is switched as per the input digital signal. This is analogous to Phase Modulation (PM).
As we know, in case of phase modulation, phase of the carrier wave is changed according to the instantaneous value of the modulating signal. In the same way, in phase shift keying also, the phase of the sinusoidal carrier wave is changed according to the digital input signal. So the basic difference between analogue modulation and digital modulation is based on the nature of the modulating signal (message signal).

Low Level and High Level Modulation Block Diagram (AM Transmitter Block Diagram)

This post is about the generation of amplitude modulation. Here we will see two different ways of generating Amplitude Modulation (AM).
So the generation of amplitude modulation (AM) can be of following two types-

Types of Amplitude Modulation Generation

Low level Amplitude Modulation
High level Amplitude Modulation

Watch the Complete Video Here-

 

Here we will understand the difference between these two types of techniques of generation of AM, with the help of block diagrams-

Low Level Amplitude Modulation (Block Diagram)

The image given below shows the block diagram of a Low Level Amplitude Modulation

Block Diagram of Low Level Amplitude Modulation 

Now observe the image carefully-
This block diagram shows 3 main blocks-
#Low level AM modulator
#Wideband power amplifier and
#RF carrier oscillator

As you can see in the diagram that low level AM modulator has two inputs. At its first input we apply the modulating signal source (message signal) and it's second input is supplied by the RF carrier oscillator.
Since it is low level amplitude modulation therefore before applying the modulating signal to the low level AM modulator, we do not amplify it. In the same way, RF carrier is also not amplified.
Therefore you observe here that in low level AM modulation, neither the modulating signal nor the RF carrier is amplified before applying to low level AM modulator.

Quadrature Phase Shift Keying Modulation (QPSK) Basics, Waveform and Benefits

What is Quadrature Phase Shift Keying (QPSK) Modulation

In the last posts we have discussed ASK, FSK and BPSK i.e. Amplitude Shift Keying, Frequency Shift Keying and Binary Phase Shift Keying. In this post, we are going to discuss Quadrature Phase Shift Keying (QPSK). It is also a kind of phase shift keying but it is different from the binary phase shift keying.

Watch the complete Video Here-

 

So here we will understand what we mean by QPSK and why it is called as Quadrature Phase Shift Keying? what is 'Quadrature' here? and what is 'binary' in binary phase shift keying. We will also see the waveform of QPSK in this post and how it is formed. Here you will also get an idea about the benefits of QPSK over other digital modulation techniques.


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#Digital Modulation Techniques (ASK, FSK, PSK, BPSK)/ Amplitude, Frequency and Phase Shift Keying

How QPSK is different from ASK, FSK and BPSK

Actually we have seen in other posts on ASK, FSK, and BPSK that in these digital modulation techniques, the carrier wave assumes one of two possible states (symbols). Actually each discrete state of the carrier is called as symbol.

Pulse Code Modulation (PCM) Vs Differential Pulse Code Modulation (DPCM)

Following are the differences between Pulse Code Modulation (PCM) and Differential Pulse Code Modulation (DPCM) based on the Following Parameters

1. Number of Bits

PCM- It can use 4, 8 or 16 bits per sample
DPCM- Bits can be more than one but are less than PCM.

2. Transmission Bandwidth

PCM- Bandwidth required is very high as number of bits are high
DPCM- Bandwidth required is lower than PCM.

3. Levels and Step Size

PCM- Number of levels are dependent on number of bits and step size is kept constant
DPCM- In Differential Pulse Code Modulation (DPCM), fixed number of levels are used.

4. Quantization Error and Distortion

PCM- In pulse code modulation, quantization error depends on number of levels used.
DPCM- In differential pulse code modulation, slope overload distortion and quantization noise is present.

5. Feedback

PCM- Feedback is not present in pulse code modulation in transmitter or receiver.
DPCM- In this case, feedback exists

6. Complexity

PCM- System of pulse code modulation is quite complex
DPCM- Differential pulse code modulation system is comparatively simple.

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Need and benefits of modulation
Pulse modulation techniques (PAM, PWM, PPM, PCM)
Comparison of PAM, PWM, PPM modulation techniques
Pulse amplitude modulation (PAM)
Pulse width modulation (PWM)
Pulse position modulation (PPM) 
Pulse code modulation (PCM) advantages and disadvantages
Pulse code modulation (PCM) vs differential pulse code modulation (DPCM)
Sampling theorem and reconstruction (sampling and quantization)

Digital Modulation Techniques (Coherent and Non-Coherent Digital Modulation Techniques)

Coherent Vs Non Coherent Modulation (Introduction)

On the Basis of presence of Phase-Recovery circuit, we can classify digital modulation techniques into coherent or non coherent techniques.

Watch the Complete Video Here-

 

The job of the phase recovery circuit is to keep the oscillators supplying locally generated carrier wave at the receiver; in synchronizm to the oscillator supplying carrier wave at the transmitting end.
Actually, We use carrier waves at the transmitting and receiving ends both and for coherent detection these two Carriers should be in synchronism. Here synchronism means, synchronization in both frequency and phase.

Quadrature Amplitude Modulation (QAM)/ QAM Transmitter and QAM Receiver Block Diagram

In this post, we will discuss the Quadrature Amplitude Modulation (QAM). Here we will see, the basic concept of quadrature amplitude modulation and why it is known as quadrature amplitude modulation. The block diagram of QAM transmitter and receiver also has been explained here.

Watch the Complete Video Here-

 

Introduction of Quadrature Amplitude Modulation (QAM)

Quadrature Amplitude Modulation (QAM) can be used, either with analog signals or digital signals. If the message signal is analog in nature, then we use it with Amplitude Modulation (AM) but when the message signal is in digital form, then Amplitude Shift Keying (ASK) is used.

Amplitude Modulation Vs Frequency Modulation | AM Vs FM | Advantages and Disadvantages of AM and FM

What is Amplitude Modulation (AM)

Definition:-

Amplitude Modulation, is a system, where the maximum amplitude of the carrier wave varies, according to the instantaneous value (amplitude) of the modulating (message or baseband) signal.

What is Frequency Modulation (FM) 

In case of Frequency Modulation (FM) the frequency of the carrier wave varies according to the instantaneous value of the modulating (message) signal.

Comparison of AM and FM (AM vs FM)

Why FM is better than AM

Following reasons make the Frequency Modulation (FM) better than Amplitude Modulation (AM)

1.FM broadcasts operate in upper VHF (Very High Frequency) and UHF (Ultra High Frequency) ranges, while MF (Medium Frequency) and HF (High Frequency) ranges are used by AM broadcasts. This is a big advantage for FM, since in VHF and UHF frequency ranges there is less noise interference.

AM vs FM Video (Comparison of AM and FM) Video

 

2.FM receivers are more immune to noise in comparison to AM receivers. since FM receivers may be fitted with amplitude limiters. These amplitude limiters can remove the amplitude variations caused by the noise.

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#AMPLITUDE MODULATION (TIME DOMAIN EQUATIONS AND WAVEFORMS)

3.In FM, it is possible to further reduce noise by increasing frequency deviation. This is not possible in case of AM, since in AM, we can not exceed 100℅ modulation without Severe distortions.

4.Standard Frequency allocations provide a guard band between commercial FM stations. This leads to less interference between adjacent channels in FM in comparison to AM.

5.In case of FM, all the transmitted power is useful but in AM, most of the power is present in carrier, that does not contain any information.

Pulse Code Modulation (PCM) | Advantages and Disadvantages of PCM | (Includes Video)

Pulse Code Modulation (PCM) is the digital form of pulse modulation technique. This form of pulse modulation technique is known as Pulse Code Modulation (PCM). Pulse code modulation is a technique to convert analog signals into digital signals.

Pulse Code Modulation (PCM) Video

 

After converting the signal into digital form, it becomes possible to transmit the digital signal through digital communication network and at the receiving end, it is converted back into it's original analog form.

Pulse code modulation process involves the following three stages -

1.Sampling of the signal

2.Quantization and

3.Coding

Advantages of Pulse Code Modulation (PCM)

1.Very high noise immunity
2.In pulse code modulation repeaters are used between the transmitter and receiver. Repeaters are used to regenerate the received PCM signal. Use of repeaters is possible due to digital nature of the signal.
3.Effect of noise is further reduced due to the use of repeaters.
4.Due to its digital nature we can easily store PCM signals.
5.One more advantage of using PCM is security of the signal. We can use various kinds of coding techniques so that only the desired person can decode the received signal.

Disadvantages of Pulse Code Modulation (PCM)

1.Pulse code modulation requires large bandwidth as compared to other techniques.
2.The encoding, decoding and quantizing circuitry of PCM is quite complex.

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Need and benefits of modulation
Pulse modulation techniques (PAM, PWM, PPM, PCM)
Comparison of PAM, PWM, PPM modulation techniques
Pulse amplitude modulation (PAM)
Pulse width modulation (PWM)
Pulse position modulation (PPM) 
Pulse code modulation (PCM) advantages and disadvantages
Pulse code modulation (PCM) vs differential pulse code modulation (DPCM)
Sampling theorem and reconstruction (sampling and quantization)

What is Modulation and why Modulation is Required | Need and Benefits of Modulation

Before understanding the need and benefits of modulation, it is important to know, what is modulation?

What is Modulation

Modulation is a process by which some characteristic (amplitude/frequency/phase) of a high frequency carrier wave is varied, in accordance with the instantaneous value of the message signal (modulating signal/ baseband signal).

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COMPARISON OF PAM, PWM, PPM MODULATION TECHNIQUES

Now let's write down the benefits of modulation. We will discuss each point in detail one by one-

What is Modulation and Why Modulation is Required Video [HD]

 

Need and Benefits of Modulation

1.To remove interference problem
2.Practical height of the antenna
3.Possibility of multiplexing
4.Long distance communication
5.Improved signal quality at the receiver

1.To Remove Interference Problem

Modulation helps in removing the interference problem by allocating a separate frequency band to different signal transmissions.

Because of this it becomes possible for many stations to transmit their message signals simultaneously without any interference.

Ex. The transmission range for audio signals is 20Hz-20kHz.

2.Practical Height of the Antenna

The height of antenna used for transmission and reception of the signal also depends on the process of modulation. The transmitting and receiving Antennas must have lengths, comparable to a quarter wavelength (λ/4) of the frequency used for transmission.

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#Digital Modulation Techniques (ASK, FSK, PSK, BPSK)/ Amplitude, Frequency and Phase Shift Keying

To understand how the frequency used for transmission of the signal affects the height of the antenna. 
As mentioned earlier, height of the antenna should be comparable to λ/4 of the frequency used for transmission.
height of the antenna= λ/4
Since we know that-
c=λ.f
here c is speed of light in vacuum= 3×10^8 m/s
f is frequency
Therefore λ= c/f
So height of the antenna would be-
(c/f).(1/4) 
here c and 1/4 are constants
Therefore antenna height is inversely proportional to frequency used for transmission.
It means as the frequency of modulation increases, height of the antenna used for transmission decreases.
We Will understand it will the help of an example-
Here we will see, how the height of the antenna reduced when we increased the frequency used for transmission from 4kHz to 5MHz after modulation. 
Height= λ/4
             =(c/f).(1/4)
             = (3×10^8 m/s)/(4×10^3Hz)× (1/4)
=0.187×10^5 meters
= 18.7 kilometers !!!
This height of antenna is not practical.
After modulation-
Frequency used is 5MHz
H=(c/f).(1/4)
   =(3×10^8 m/s)/(5×10^6Hz)× (1/4)
=0.15×10^2 meters
15meters
It is practical height of the antenna.

3.Possibility of Multiplexing

Multiplexing can be Defined as a process by which two or more signals can be transmitted simultaneously over the same channel for communication.
Modulation can be used to allocate separate frequency bands by using career waves of different frequencies. This type of multiplexing is known as Frequency division multiplexing (FDM).

4.Long Distance Communication

Modulation is used for long distance communication. In modulation we use high frequency carrier wave for transmission of the message signal. 

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#ADVANTAGES AND DISADVANTAGES OF DIGITAL COMMUNICATION SYSTEM

High frequency signals attenuate less as compared to low frequency signals. Therefore moderation is beneficial for long distance communication.

5.Improved Signal Quality At The Receiver

Some techniques of modulation like Frequency Modulation (FM), Pulse Code Modulation (PCM) have the capability to improve quality of the signal received at the receiving end. So it helps in reducing the noise level in the signal, which is a big advantage of modulation.

Read More:

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Need and benefits of modulation
Amplitude modulation (time domain equations and waveforms)
Frequency spectrum of amplitude modulation (waveforms and equations derivation)
Amplitude modulation vs frequency modulation (advantages and disadvantages)
Conventional AM vs DSB-SC vs SSB-SC vs VSB (comparison of AM systems)
Low level and high level modulation block diagram (AM transmitter block diagram)
Frequency translation / frequency mixing / frequency conversion / heterodyning (basic concepts and need)

PULSE POSITION MODULATION (PPM) - Basics, Definition and Waveform of PPM

Pulse modulation can be categorized broadly into two types-
#Analog modulation and
#Digital modulation
The analog pulse modulation can again be of two types-

Pulse Position Modulation Video [HD]

 

#Pulse Amplitude Modulation (PAM)
#Pulse Time Modulation (PTM)
The Pulse Time Modulation (PTM) can further be classified into two types of modulation-
#Pulse Width Modulation (PWM)/Pulse Duration Modulation (PDM)
#Pulse Position Modulation (PPM)
Pulse Code Modulation (PCM) is a digital pulse modulation technique.

Pulse Width Modulation (PWM) - Basic Concepts, Waveform and Definition of PWM Explained

What is Pulse Modulation

Pulse modulation is a type of modulation where some parameter of the pulsed carrier wave is varied as per the instantaneous value of the modulating signal (message signal).

Types of Pulse Modulation Techniques

Pulse modulation can be categorized into 3 types-
1.Pulse Amplitude Modulation (PAM)
2.Pulse Width Modulation (PWM)
3.Pulse Position Modulation (PPM)

Out of these three types of pulse modulation techniques, PWM and PPM come under Pulse Time Modulation (PTM).

Pulse Width Modulation Video [HD]

 

Pulse Time Modulation (PTM)

In pulse time modulation, the timing of pulses of the pulsed carrier is varied. So the variations occur on the time axis. Since it is of two types, Pulse Width Modulation and Pulse Position Modulation, where width and position of the pulses is varied respectively. These changes in width or position take place on the time axis. Therefore PWM and PPM are types of pulse time modulation.

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COMPARISON OF PAM, PWM, PPM MODULATION TECHNIQUES

Now we will understand the Pulse Width Modulation (PWM), in detail-

Pulse Width Modulation (PWM)

Definition:-

In Pulse width modulation, width (duration) of the pulses of the carrier wave is varied according to the modulating signal (message signal).

Let's analyze the waveform of pulse width modulation.
Look at the image given below to see the waveform of pulse width modulated signal. (Click the image to enlarge)-

Pulse Width Modulation Waveform (PWM)

Here you can see waveforms of modulating signal, pulsed carrier wave and pulse width modulated wave.

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#PULSE CODE MODULATION (PCM) [ADVANTAGES AND DISADVANTAGES]
#Quadrature Amplitude Modulation (QAM)/ QAM Transmitter and QAM Receiver Block Diagram

As per the definition of pulse width modulation, we know that, in Pulse width modulation, the width of the pulses of carrier wave is varied according to the message signal. So you can see here in the image that as the amplitude of the message signal changes, the width of pulses of the pulsed carrier wave changes accordingly.
You can easily observe here, the width of the pulse is maximum when amplitude of the message signal is at maximum and in the same way, width is minimum when amplitude of the modulating signal is minimum.

Important Observations about Pulse Width Modulation (PWM)

1.Since it is pulse width modulation (pulse duration modulation), therefore only the width (duration) of the pulses of the carrier wave changes. No change takes place in amplitude or position of the pulses.

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#Watch the VIDEOS PLAYLIST here (Pulse modulation Techniques)

2.As the width of pulses changes according to the modulating signal; information is present only in the width of the pulses. In Pulse width modulation, amplitude or position of the pulses contain no information.

Properties of Pulse Width Modulation (PWM) 

1.Power in PWM

In PWM, instantaneous power of the transmitter varies due to variations in width of the pulses.

2.Noise in PWM 

Pulse Width Modulation is less affected by noise due to its constant amplitude. It is also easier to remove noise from the signal as compared to Pulse amplitude modulation.

3.Similarity of PWM with Continuous Wave Modulation

The pulse width modulation is very similar to Frequency Modulation (FM). Since in frequency modulation, frequency of the carrier wave varies according to instantaneous value the of the modulating signal. 
f=1/T 
i.e. frequency is inversely proportional to the time period.
Similarity in PWM, the duration (time period/time duration) varies.

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Need and benefits of modulation
Pulse modulation techniques (PAM, PWM, PPM, PCM)
Comparison of PAM, PWM, PPM modulation techniques
Pulse amplitude modulation (PAM)
Pulse width modulation (PWM)
Pulse position modulation (PPM) 
Pulse code modulation (PCM) advantages and disadvantages
Pulse code modulation (PCM) vs differential pulse code modulation (DPCM)
Sampling theorem and reconstruction (sampling and quantization)

PULSE AMPLITUDE MODULATION (PAM) || Definition, Basics and Waveform of PAM Explained

In this post we will discuss Pulse Amplitude Modulation (PAM). Pulse Amplitude Modulation is a pulse modulation technique. Other techniques of analog pulse modulation are- Pulse Width Modulation (PWM) and Pulse Position Modulation (PPM). But before discussing pulse amplitude modulation, it is important to know, what is pulse modulation and how it is different from continuous wave modulation.

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#NEED AND BENEFITS OF MODULATION

Pulse Amplitude Modulation Video [HD]

 

Difference between Pulse Modulation and Continuous Wave Modulation

In pulse modulation, some parameter (amplitude, width or position) of the pulsed carrier wave is varied as per the instantaneous value of the modulating signal (message signal). Types of analog pulse modulation techniques are- Pulse Amplitude Modulation (PAM), Pulse Width Modulation (PWM) and Pulse Position Modulation (PPM).

While continuous wave modulation is a technique of modulation where some parameter (amplitude, frequency or phase) of a sinusoidal carrier is varied in accordance with the instantaneous value of the  modulating signal. 

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COMPARISON OF PAM, PWM, PPM MODULATION TECHNIQUES

Types of continuous wave modulation are- Amplitude modulation (AM), Frequency Modulation (FM) and Phase Modulation (PM).

See the image given below to understand different types of modulation techniques. Click the image to enlarge it-

Classification of Modulation Techniques

Classification of Modulation Techniques

The definitions of PAM, PWM and PPM are given below for quick reference-

Pulse Amplitude Modulation (PAM)

In pulse amplitude modulation, the amplitude of pulsed carrier wave is varied according to the modulating signal.

Pulse Time Modulation (PTM)

In pulse time modulation, the timing of pulses of the pulsed carrier is varied. Therefore the variations in the pulse are on the time axis.

Pulse Time Modulation (PTM) is of two types-

Pulse Width Modulation (PWM)/ Pulse Duration modulation (PDM) and

Pulse Position Modulation (PPM)

Pulse Width Modulation (PWM)

In PWM, the width of pulsed carrier wave is varied as per the instantaneous value of the modulating signal.

Pulse Position Modulation (PPM)

In PPM, the position of pulsed carrier is varied as per the modulating signal (message signal).

Now we understand the basic difference between PAM, PWM and PPM. Now it's time to discuss pulse Amplitude Modulation in some detail-

Pulse Amplitude Modulation (PAM)

Definition:-

The modulation technique in which the instantaneous amplitude of the pulsed carrier is varied according to the modulating signal (message signal) is called as pulse amplitude modulation (PAM).

Waveform of Pulse Amplitude Modulation (PAM)

Look at the image given below carefully to understand the formation of pulse amplitude modulated wave. (Click the image to enlarge)-

Pulse Amplitude Modulation (PAM) Waveform

Here in this image, you can see, three waveforms.

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#Watch the VIDEOS PLAYLIST here (Pulse modulation Techniques)

The first waveform is of modulating signal (message signal), the second one is of the pulsed career wave and the third waveform is of the pulse amplitude modulated wave (PAM).

The message signal can have multiple frequencies and variable amplitude. Here we have used a sinusoidal message signal. The carrier wave that we have used here, is a train of pulses having high frequency. Since we know that in Pulse modulation, the carrier wave is in the form of pulses.

Now we will understand how can we make pulse amplitude modulated wave (PAM).

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#AMPLITUDE MODULATION (TIME DOMAIN EQUATIONS AND WAVEFORMS)
#FREQUENCY SPECTRUM OF AMPLITUDE MODULATION (WAVEFORMS AND EQUATIONS DERIVATION)

As we have discussed that in Pulse amplitude modulation, the instantaneous amplitude of the pulsed carrier is varied according to the modulating signal (message signal). Now look at the image shown above very carefully, observe that, as the amplitude of the modulating signal (message signal or baseband signal) increases, the amplitude of the pulsed carrier wave increases and becomes maximum when the amplitude of the modulating signal reaches at its maximum. Now the amplitude of the carrier wave starts decreasing with decrease in amplitude of the modulating signal. So it is clear from the image that the amplitude of the pulsed carrier wave varies according to the instantaneous value of the message signal.

Important Observations about Pulse Amplitude Modulation (PAM)

#As it is Pulse Amplitude Modulation (PAM), therefore only the amplitude of the pulsed carrier changes. 

#There is no change in the width or position of the pulsed carrier wave. So the width and position of the carrier wave pulse is constant here.

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#Digital Modulation Techniques (ASK, FSK, PSK, BPSK)/ Amplitude, Frequency and Phase Shift Keying

#Therefore all the information of the modulating signal is contained in the amplitude variations of the pulses. No information is present in the width or position of the pulses.

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Need and benefits of modulation
Pulse modulation techniques (PAM, PWM, PPM, PCM)
Comparison of PAM, PWM, PPM modulation techniques
Pulse amplitude modulation (PAM)
Pulse width modulation (PWM)
Pulse position modulation (PPM) 
Pulse code modulation (PCM) advantages and disadvantages
Pulse code modulation (PCM) vs differential pulse code modulation (DPCM)
Sampling theorem and reconstruction (sampling and quantization)