SlideShare a Scribd company logo
1 of 15
BY:
MD. AHSAN HALIMI
M.TECH - ECE
DIGITAL MODULATION (QAM)
MODULATION OF DIGITAL DATA
Modulation – Process of converting digital data or a low-pass analog
signal to band-pass (higher-frequency) analog signal.
DIGITAL-TO-ANALOG MODULATION
Process of changing one of the characteristic of an analog signal
(typically a sinewave) based on the information in a digital signal.
Sinewave is defined by 3 characteristics (amplitude, frequency, and
phase) ⇒ digital data (binary 0 & 1) can be represented by varying
any of the three.
TYPES OF DIGITAL-TO-ANALOG
MODULATION
ITRODUCTION ‐QAM
 Quadrature Amplitude Modulation or QAM is a form of modulation
which is widely used for modulating data signals onto a carrier used for
radio communications.
 It is widely used because it offers advantages over other forms
of data modulation such as PSK, although many forms of data
modulation operate along side each other.
 Quadrature Amplitude Modulation, QAM is a signal in which two
carriers shifted in phase by 90 degrees are modulated and the resultant
output consists of both amplitude and phase variations. In view of the
fact that both amplitude and phase variations are present it may also be
considered as a mixture of amplitude and phase.
Bk
Sin(Wct)
Ak
Cos(Wct)
BLOCK DIAGRAM OF QAM MODULATION
QAM APPLICATIONS
QAM is in many radio communications and data delivery
applications. However some specific variants of QAM are used in
some specific applications and standards.
For domestic broadcast applications for example, 64 QAM and 256
QAM are often used in digital cable television and cable modem
applications. In the UK, 16 QAM and 64 QAM are currently used for
digital terrestrial television using DVB Digital Video Broadcasting. In
the US, 64 QAM and 256 QAM are the mandated modulation schemes
for digital cable as standardised by the SCTE in the standard
ANSI/SCTE 07 2000.
In addition to this, variants of QAM are also used for many wireless
and cellular technology applications.
ADVANTAGES OF QAM
QAM appears to increase the efficiency of transmission for radio.
communications systems by utilizing both amplitude and phase
variations,
DISADVANTAGES OF QAM
more susceptible to noise because the states are closer together so that a
lower.
level of noise is needed to move the signal to a different decision point.
Receivers for use with phase or frequency modulation are both able to use
limiting amplifiers that are able to remove any amplitude noise and thereby
improve the noise reliance. This is not the case with QAM.
 The second limitation is also associated with the amplitude component of
the signal. When a phase or frequency modulated signal is amplified in a
radio transmitter, there is no need to use linear amplifiers, whereas when
using QAM that contains an amplitude component, linearity must be
maintained. Unfortunately linear amplifiers are less efficient and consume
more power, and this makes them less attractive for mobile applications.
CONSTELLATION DIAGRAMS FOR QAM
Quadrature amplitude modulation, QAM, when used for digital
transmission for radio communications applications is able to carry
higher data rates than ordinary amplitude modulated schemes and
phase modulated schemes. As with phase shift keying, etc, the number
of points at which the signal can rest, i.e. the number of points on the
constellation is indicated in the modulation format description, e.g.
16QAM uses a 16 point constellation.
When using QAM, the constellation points are normally arranged in a
square grid with equal vertical and horizontal spacing and as a result
the most common forms of QAM use a constellation with the number
of points equal to a power of 2 i.e. 2, 4, 8, 16 . . . .
By using higher order modulation formats, i.e. more points on the
constellation, it is possible to transmit more bits per symbol. However
the points are closer together and they are therefore more
susceptible to noise and data errors.
To provide an example of how QAM operates, the table below
provides the bit sequences, and the associated amplitude and phase
states. From this it can be seen that a continuous bit stream may be
grouped into threes and represented as a sequence of eight
permissible states.
The constellation diagrams show the different positions for the states
within different forms of QAM, quadrature amplitude modulation. As
the order of the modulation increases, so does the number of points
on the QAM constellation diagram.
The diagrams below show constellation diagrams for a variety of
formats of modulation:
WHY QAM CALLED COMBINED ASK AND PSK
Quadrature Amplitude Modulation uses the phase and amplitude of the
carrier signal to encode data. QAM finds widespread use in current and
emerging wireless standards, including Wi-Fi, Digital Video Broadcast
(DVB), WiMAX, IEEE 802.11n, and HSDPA/HSUPA.
The QAM modulation scheme encodes data by varying both amplitude and
phase of the carrier signal. Thus, it is sometimes viewed as a combination of
ASK and PSK modulation.
A modulated carrier signal can be expressed in terms of it’s components as:
AcCos(2*pi*fc*t+θ) =ICos(2*pi*fc*t) - QSin(2*pi*fc*t)
Where I = Ac Cosθ and Ac Sinθ
Q=Ac Sinθ
Conclusion
 Quadrature Amplitude Modulation is an important modulation
scheme with many practical applications, including current and future
wireless technologies. Some examples of communication systems that
use QAM are Wi‐Fi, cable modems, Digital Video Broadcast (DVB)
and WiMAX.
QUADRATURE AMPLITUDE MODULATION

More Related Content

What's hot

Diversity Techniques in Wireless Communication
Diversity Techniques in Wireless CommunicationDiversity Techniques in Wireless Communication
Diversity Techniques in Wireless CommunicationSahar Foroughi
 
Frequency modulation
Frequency modulationFrequency modulation
Frequency modulationgopi789
 
Pulse Modulation ppt
Pulse Modulation pptPulse Modulation ppt
Pulse Modulation pptsanjeev2419
 
Digital Modulation Unit 3
Digital Modulation Unit 3Digital Modulation Unit 3
Digital Modulation Unit 3Anil Nigam
 
2. wireless propagation models free space propagation
2. wireless propagation models   free space propagation2. wireless propagation models   free space propagation
2. wireless propagation models free space propagationJAIGANESH SEKAR
 
Phase Shift Keying & π/4 -Quadrature Phase Shift Keying
Phase Shift Keying & π/4 -Quadrature Phase Shift KeyingPhase Shift Keying & π/4 -Quadrature Phase Shift Keying
Phase Shift Keying & π/4 -Quadrature Phase Shift KeyingNaveen Jakhar, I.T.S
 
Digital communication systems
Digital communication systemsDigital communication systems
Digital communication systemsNisreen Bashar
 
Chap 5 (small scale fading)
Chap 5 (small scale fading)Chap 5 (small scale fading)
Chap 5 (small scale fading)asadkhan1327
 
M ary psk modulation
M ary psk modulationM ary psk modulation
M ary psk modulationAhmed Diaa
 
TWO STAGE NETWORKS
TWO STAGE NETWORKSTWO STAGE NETWORKS
TWO STAGE NETWORKSAakankshaR
 
Delta modulation
Delta modulationDelta modulation
Delta modulationmpsrekha83
 
Chapter 7 multiple access techniques
Chapter 7 multiple access techniquesChapter 7 multiple access techniques
Chapter 7 multiple access techniquesKaushal Kabra
 
Generation of SSB and DSB_SC Modulation
Generation of SSB and DSB_SC ModulationGeneration of SSB and DSB_SC Modulation
Generation of SSB and DSB_SC ModulationJoy Debnath
 
Mimo in Wireless Communication
Mimo in Wireless CommunicationMimo in Wireless Communication
Mimo in Wireless Communicationkailash karki
 

What's hot (20)

Wavelength division multiplexing
Wavelength division multiplexingWavelength division multiplexing
Wavelength division multiplexing
 
Diversity Techniques in Wireless Communication
Diversity Techniques in Wireless CommunicationDiversity Techniques in Wireless Communication
Diversity Techniques in Wireless Communication
 
Spread spectrum
Spread spectrumSpread spectrum
Spread spectrum
 
QAM
QAMQAM
QAM
 
Frequency modulation
Frequency modulationFrequency modulation
Frequency modulation
 
Frequency Modulation
Frequency ModulationFrequency Modulation
Frequency Modulation
 
Pulse Modulation ppt
Pulse Modulation pptPulse Modulation ppt
Pulse Modulation ppt
 
Digital Modulation Unit 3
Digital Modulation Unit 3Digital Modulation Unit 3
Digital Modulation Unit 3
 
2. wireless propagation models free space propagation
2. wireless propagation models   free space propagation2. wireless propagation models   free space propagation
2. wireless propagation models free space propagation
 
Phase Shift Keying & π/4 -Quadrature Phase Shift Keying
Phase Shift Keying & π/4 -Quadrature Phase Shift KeyingPhase Shift Keying & π/4 -Quadrature Phase Shift Keying
Phase Shift Keying & π/4 -Quadrature Phase Shift Keying
 
Digital communication systems
Digital communication systemsDigital communication systems
Digital communication systems
 
Chap 5 (small scale fading)
Chap 5 (small scale fading)Chap 5 (small scale fading)
Chap 5 (small scale fading)
 
Pulse modulation
Pulse modulationPulse modulation
Pulse modulation
 
M ary psk modulation
M ary psk modulationM ary psk modulation
M ary psk modulation
 
TWO STAGE NETWORKS
TWO STAGE NETWORKSTWO STAGE NETWORKS
TWO STAGE NETWORKS
 
Chapter 5
Chapter 5Chapter 5
Chapter 5
 
Delta modulation
Delta modulationDelta modulation
Delta modulation
 
Chapter 7 multiple access techniques
Chapter 7 multiple access techniquesChapter 7 multiple access techniques
Chapter 7 multiple access techniques
 
Generation of SSB and DSB_SC Modulation
Generation of SSB and DSB_SC ModulationGeneration of SSB and DSB_SC Modulation
Generation of SSB and DSB_SC Modulation
 
Mimo in Wireless Communication
Mimo in Wireless CommunicationMimo in Wireless Communication
Mimo in Wireless Communication
 

Similar to QUADRATURE AMPLITUDE MODULATION

QAM Microsoft PowerPoint جديد.pptx
QAM Microsoft PowerPoint جديد.pptxQAM Microsoft PowerPoint جديد.pptx
QAM Microsoft PowerPoint جديد.pptxssuserd6ee01
 
ADAPTIVE MODULATION TECHNIQUES FOR CAPACITY IMPROVEMENT OF BER IN WCDMA
ADAPTIVE MODULATION TECHNIQUES FOR CAPACITY IMPROVEMENT OF BER IN WCDMAADAPTIVE MODULATION TECHNIQUES FOR CAPACITY IMPROVEMENT OF BER IN WCDMA
ADAPTIVE MODULATION TECHNIQUES FOR CAPACITY IMPROVEMENT OF BER IN WCDMAmirza asif haider
 
Quadrature amplitude modulation
Quadrature amplitude modulationQuadrature amplitude modulation
Quadrature amplitude modulationAanchalKumari4
 
quadrature amplitude modulation
quadrature amplitude modulationquadrature amplitude modulation
quadrature amplitude modulationtusharsinghal58
 
Analysis of FHSS-CDMA with QAM-64 over AWGN and Fading Channels
Analysis of FHSS-CDMA with QAM-64 over AWGN and Fading ChannelsAnalysis of FHSS-CDMA with QAM-64 over AWGN and Fading Channels
Analysis of FHSS-CDMA with QAM-64 over AWGN and Fading ChannelsIRJET Journal
 
Modulation Techniques.pptx
Modulation Techniques.pptxModulation Techniques.pptx
Modulation Techniques.pptxVIJAYKUMARM29
 
Improving quality of service using ofdm technique for 4 th generation network
Improving quality of service using ofdm technique for 4 th generation networkImproving quality of service using ofdm technique for 4 th generation network
Improving quality of service using ofdm technique for 4 th generation networkeSAT Publishing House
 
Improving quality of service using ofdm technique for 4 th generation network
Improving quality of service using ofdm technique for 4 th generation networkImproving quality of service using ofdm technique for 4 th generation network
Improving quality of service using ofdm technique for 4 th generation networkeSAT Journals
 
Implementation of m qam modulation techniques in 4 g communication
Implementation of m qam modulation techniques in 4 g communicationImplementation of m qam modulation techniques in 4 g communication
Implementation of m qam modulation techniques in 4 g communicationShatrughanPatel1
 
Performance Evaluation of Different QAM Techniques Using Matlab/Simulink full...
Performance Evaluation of Different QAM Techniques Using Matlab/Simulink full...Performance Evaluation of Different QAM Techniques Using Matlab/Simulink full...
Performance Evaluation of Different QAM Techniques Using Matlab/Simulink full...vnktrjr
 
4g 5g document 5g day five usefull .pptx
4g 5g document 5g day five usefull .pptx4g 5g document 5g day five usefull .pptx
4g 5g document 5g day five usefull .pptxDhamoDharan66
 
Ch 04 analog and digital communications
Ch 04 analog and digital communicationsCh 04 analog and digital communications
Ch 04 analog and digital communicationssakariachromabook
 
Designing and Performance Evaluation of 64 QAM OFDM System
Designing and Performance Evaluation of 64 QAM OFDM SystemDesigning and Performance Evaluation of 64 QAM OFDM System
Designing and Performance Evaluation of 64 QAM OFDM SystemIOSR Journals
 
Designing and Performance Evaluation of 64 QAM OFDM System
Designing and Performance Evaluation of 64 QAM OFDM SystemDesigning and Performance Evaluation of 64 QAM OFDM System
Designing and Performance Evaluation of 64 QAM OFDM SystemIOSR Journals
 
dfsdfsdfIjett v4 i7p177
dfsdfsdfIjett v4 i7p177dfsdfsdfIjett v4 i7p177
dfsdfsdfIjett v4 i7p177Mhmd Alawasa
 

Similar to QUADRATURE AMPLITUDE MODULATION (20)

QAM Microsoft PowerPoint جديد.pptx
QAM Microsoft PowerPoint جديد.pptxQAM Microsoft PowerPoint جديد.pptx
QAM Microsoft PowerPoint جديد.pptx
 
ADAPTIVE MODULATION TECHNIQUES FOR CAPACITY IMPROVEMENT OF BER IN WCDMA
ADAPTIVE MODULATION TECHNIQUES FOR CAPACITY IMPROVEMENT OF BER IN WCDMAADAPTIVE MODULATION TECHNIQUES FOR CAPACITY IMPROVEMENT OF BER IN WCDMA
ADAPTIVE MODULATION TECHNIQUES FOR CAPACITY IMPROVEMENT OF BER IN WCDMA
 
205 eng105
205 eng105205 eng105
205 eng105
 
Quadrature amplitude modulation
Quadrature amplitude modulationQuadrature amplitude modulation
Quadrature amplitude modulation
 
quadrature amplitude modulation
quadrature amplitude modulationquadrature amplitude modulation
quadrature amplitude modulation
 
Analysis of FHSS-CDMA with QAM-64 over AWGN and Fading Channels
Analysis of FHSS-CDMA with QAM-64 over AWGN and Fading ChannelsAnalysis of FHSS-CDMA with QAM-64 over AWGN and Fading Channels
Analysis of FHSS-CDMA with QAM-64 over AWGN and Fading Channels
 
Modulation Techniques.pptx
Modulation Techniques.pptxModulation Techniques.pptx
Modulation Techniques.pptx
 
Improving quality of service using ofdm technique for 4 th generation network
Improving quality of service using ofdm technique for 4 th generation networkImproving quality of service using ofdm technique for 4 th generation network
Improving quality of service using ofdm technique for 4 th generation network
 
Improving quality of service using ofdm technique for 4 th generation network
Improving quality of service using ofdm technique for 4 th generation networkImproving quality of service using ofdm technique for 4 th generation network
Improving quality of service using ofdm technique for 4 th generation network
 
Bit Error rate of QAM
Bit Error rate of QAMBit Error rate of QAM
Bit Error rate of QAM
 
Implementation of m qam modulation techniques in 4 g communication
Implementation of m qam modulation techniques in 4 g communicationImplementation of m qam modulation techniques in 4 g communication
Implementation of m qam modulation techniques in 4 g communication
 
Performance Evaluation of Different QAM Techniques Using Matlab/Simulink full...
Performance Evaluation of Different QAM Techniques Using Matlab/Simulink full...Performance Evaluation of Different QAM Techniques Using Matlab/Simulink full...
Performance Evaluation of Different QAM Techniques Using Matlab/Simulink full...
 
Project report
Project reportProject report
Project report
 
4g 5g document 5g day five usefull .pptx
4g 5g document 5g day five usefull .pptx4g 5g document 5g day five usefull .pptx
4g 5g document 5g day five usefull .pptx
 
Lecture 4
Lecture 4Lecture 4
Lecture 4
 
Ch 04 analog and digital communications
Ch 04 analog and digital communicationsCh 04 analog and digital communications
Ch 04 analog and digital communications
 
Designing and Performance Evaluation of 64 QAM OFDM System
Designing and Performance Evaluation of 64 QAM OFDM SystemDesigning and Performance Evaluation of 64 QAM OFDM System
Designing and Performance Evaluation of 64 QAM OFDM System
 
Designing and Performance Evaluation of 64 QAM OFDM System
Designing and Performance Evaluation of 64 QAM OFDM SystemDesigning and Performance Evaluation of 64 QAM OFDM System
Designing and Performance Evaluation of 64 QAM OFDM System
 
Ijetcas14 585
Ijetcas14 585Ijetcas14 585
Ijetcas14 585
 
dfsdfsdfIjett v4 i7p177
dfsdfsdfIjett v4 i7p177dfsdfsdfIjett v4 i7p177
dfsdfsdfIjett v4 i7p177
 

Recently uploaded

Theory of Time 2024 (Universal Theory for Everything)
Theory of Time 2024 (Universal Theory for Everything)Theory of Time 2024 (Universal Theory for Everything)
Theory of Time 2024 (Universal Theory for Everything)Ramkumar k
 
Path loss model, OKUMURA Model, Hata Model
Path loss model, OKUMURA Model, Hata ModelPath loss model, OKUMURA Model, Hata Model
Path loss model, OKUMURA Model, Hata ModelDrAjayKumarYadav4
 
Worksharing and 3D Modeling with Revit.pptx
Worksharing and 3D Modeling with Revit.pptxWorksharing and 3D Modeling with Revit.pptx
Worksharing and 3D Modeling with Revit.pptxMustafa Ahmed
 
Independent Solar-Powered Electric Vehicle Charging Station
Independent Solar-Powered Electric Vehicle Charging StationIndependent Solar-Powered Electric Vehicle Charging Station
Independent Solar-Powered Electric Vehicle Charging Stationsiddharthteach18
 
Presentation on Slab, Beam, Column, and Foundation/Footing
Presentation on Slab,  Beam, Column, and Foundation/FootingPresentation on Slab,  Beam, Column, and Foundation/Footing
Presentation on Slab, Beam, Column, and Foundation/FootingEr. Suman Jyoti
 
Autodesk Construction Cloud (Autodesk Build).pptx
Autodesk Construction Cloud (Autodesk Build).pptxAutodesk Construction Cloud (Autodesk Build).pptx
Autodesk Construction Cloud (Autodesk Build).pptxMustafa Ahmed
 
5G and 6G refer to generations of mobile network technology, each representin...
5G and 6G refer to generations of mobile network technology, each representin...5G and 6G refer to generations of mobile network technology, each representin...
5G and 6G refer to generations of mobile network technology, each representin...archanaece3
 
Max. shear stress theory-Maximum Shear Stress Theory ​ Maximum Distortional ...
Max. shear stress theory-Maximum Shear Stress Theory ​  Maximum Distortional ...Max. shear stress theory-Maximum Shear Stress Theory ​  Maximum Distortional ...
Max. shear stress theory-Maximum Shear Stress Theory ​ Maximum Distortional ...ronahami
 
Filters for Electromagnetic Compatibility Applications
Filters for Electromagnetic Compatibility ApplicationsFilters for Electromagnetic Compatibility Applications
Filters for Electromagnetic Compatibility ApplicationsMathias Magdowski
 
Adsorption (mass transfer operations 2) ppt
Adsorption (mass transfer operations 2) pptAdsorption (mass transfer operations 2) ppt
Adsorption (mass transfer operations 2) pptjigup7320
 
engineering chemistry power point presentation
engineering chemistry  power point presentationengineering chemistry  power point presentation
engineering chemistry power point presentationsj9399037128
 
21P35A0312 Internship eccccccReport.docx
21P35A0312 Internship eccccccReport.docx21P35A0312 Internship eccccccReport.docx
21P35A0312 Internship eccccccReport.docxrahulmanepalli02
 
Introduction-to- Metrology and Quality.pptx
Introduction-to- Metrology and Quality.pptxIntroduction-to- Metrology and Quality.pptx
Introduction-to- Metrology and Quality.pptxProfASKolap
 
NEWLETTER FRANCE HELICES/ SDS SURFACE DRIVES - MAY 2024
NEWLETTER FRANCE HELICES/ SDS SURFACE DRIVES - MAY 2024NEWLETTER FRANCE HELICES/ SDS SURFACE DRIVES - MAY 2024
NEWLETTER FRANCE HELICES/ SDS SURFACE DRIVES - MAY 2024EMMANUELLEFRANCEHELI
 
UNIT 4 PTRP final Convergence in probability.pptx
UNIT 4 PTRP final Convergence in probability.pptxUNIT 4 PTRP final Convergence in probability.pptx
UNIT 4 PTRP final Convergence in probability.pptxkalpana413121
 
Dynamo Scripts for Task IDs and Space Naming.pptx
Dynamo Scripts for Task IDs and Space Naming.pptxDynamo Scripts for Task IDs and Space Naming.pptx
Dynamo Scripts for Task IDs and Space Naming.pptxMustafa Ahmed
 
Basics of Relay for Engineering Students
Basics of Relay for Engineering StudentsBasics of Relay for Engineering Students
Basics of Relay for Engineering Studentskannan348865
 
Involute of a circle,Square, pentagon,HexagonInvolute_Engineering Drawing.pdf
Involute of a circle,Square, pentagon,HexagonInvolute_Engineering Drawing.pdfInvolute of a circle,Square, pentagon,HexagonInvolute_Engineering Drawing.pdf
Involute of a circle,Square, pentagon,HexagonInvolute_Engineering Drawing.pdfJNTUA
 
History of Indian Railways - the story of Growth & Modernization
History of Indian Railways - the story of Growth & ModernizationHistory of Indian Railways - the story of Growth & Modernization
History of Indian Railways - the story of Growth & ModernizationEmaan Sharma
 
Artificial Intelligence in due diligence
Artificial Intelligence in due diligenceArtificial Intelligence in due diligence
Artificial Intelligence in due diligencemahaffeycheryld
 

Recently uploaded (20)

Theory of Time 2024 (Universal Theory for Everything)
Theory of Time 2024 (Universal Theory for Everything)Theory of Time 2024 (Universal Theory for Everything)
Theory of Time 2024 (Universal Theory for Everything)
 
Path loss model, OKUMURA Model, Hata Model
Path loss model, OKUMURA Model, Hata ModelPath loss model, OKUMURA Model, Hata Model
Path loss model, OKUMURA Model, Hata Model
 
Worksharing and 3D Modeling with Revit.pptx
Worksharing and 3D Modeling with Revit.pptxWorksharing and 3D Modeling with Revit.pptx
Worksharing and 3D Modeling with Revit.pptx
 
Independent Solar-Powered Electric Vehicle Charging Station
Independent Solar-Powered Electric Vehicle Charging StationIndependent Solar-Powered Electric Vehicle Charging Station
Independent Solar-Powered Electric Vehicle Charging Station
 
Presentation on Slab, Beam, Column, and Foundation/Footing
Presentation on Slab,  Beam, Column, and Foundation/FootingPresentation on Slab,  Beam, Column, and Foundation/Footing
Presentation on Slab, Beam, Column, and Foundation/Footing
 
Autodesk Construction Cloud (Autodesk Build).pptx
Autodesk Construction Cloud (Autodesk Build).pptxAutodesk Construction Cloud (Autodesk Build).pptx
Autodesk Construction Cloud (Autodesk Build).pptx
 
5G and 6G refer to generations of mobile network technology, each representin...
5G and 6G refer to generations of mobile network technology, each representin...5G and 6G refer to generations of mobile network technology, each representin...
5G and 6G refer to generations of mobile network technology, each representin...
 
Max. shear stress theory-Maximum Shear Stress Theory ​ Maximum Distortional ...
Max. shear stress theory-Maximum Shear Stress Theory ​  Maximum Distortional ...Max. shear stress theory-Maximum Shear Stress Theory ​  Maximum Distortional ...
Max. shear stress theory-Maximum Shear Stress Theory ​ Maximum Distortional ...
 
Filters for Electromagnetic Compatibility Applications
Filters for Electromagnetic Compatibility ApplicationsFilters for Electromagnetic Compatibility Applications
Filters for Electromagnetic Compatibility Applications
 
Adsorption (mass transfer operations 2) ppt
Adsorption (mass transfer operations 2) pptAdsorption (mass transfer operations 2) ppt
Adsorption (mass transfer operations 2) ppt
 
engineering chemistry power point presentation
engineering chemistry  power point presentationengineering chemistry  power point presentation
engineering chemistry power point presentation
 
21P35A0312 Internship eccccccReport.docx
21P35A0312 Internship eccccccReport.docx21P35A0312 Internship eccccccReport.docx
21P35A0312 Internship eccccccReport.docx
 
Introduction-to- Metrology and Quality.pptx
Introduction-to- Metrology and Quality.pptxIntroduction-to- Metrology and Quality.pptx
Introduction-to- Metrology and Quality.pptx
 
NEWLETTER FRANCE HELICES/ SDS SURFACE DRIVES - MAY 2024
NEWLETTER FRANCE HELICES/ SDS SURFACE DRIVES - MAY 2024NEWLETTER FRANCE HELICES/ SDS SURFACE DRIVES - MAY 2024
NEWLETTER FRANCE HELICES/ SDS SURFACE DRIVES - MAY 2024
 
UNIT 4 PTRP final Convergence in probability.pptx
UNIT 4 PTRP final Convergence in probability.pptxUNIT 4 PTRP final Convergence in probability.pptx
UNIT 4 PTRP final Convergence in probability.pptx
 
Dynamo Scripts for Task IDs and Space Naming.pptx
Dynamo Scripts for Task IDs and Space Naming.pptxDynamo Scripts for Task IDs and Space Naming.pptx
Dynamo Scripts for Task IDs and Space Naming.pptx
 
Basics of Relay for Engineering Students
Basics of Relay for Engineering StudentsBasics of Relay for Engineering Students
Basics of Relay for Engineering Students
 
Involute of a circle,Square, pentagon,HexagonInvolute_Engineering Drawing.pdf
Involute of a circle,Square, pentagon,HexagonInvolute_Engineering Drawing.pdfInvolute of a circle,Square, pentagon,HexagonInvolute_Engineering Drawing.pdf
Involute of a circle,Square, pentagon,HexagonInvolute_Engineering Drawing.pdf
 
History of Indian Railways - the story of Growth & Modernization
History of Indian Railways - the story of Growth & ModernizationHistory of Indian Railways - the story of Growth & Modernization
History of Indian Railways - the story of Growth & Modernization
 
Artificial Intelligence in due diligence
Artificial Intelligence in due diligenceArtificial Intelligence in due diligence
Artificial Intelligence in due diligence
 

QUADRATURE AMPLITUDE MODULATION

  • 1. BY: MD. AHSAN HALIMI M.TECH - ECE DIGITAL MODULATION (QAM)
  • 2. MODULATION OF DIGITAL DATA Modulation – Process of converting digital data or a low-pass analog signal to band-pass (higher-frequency) analog signal.
  • 3. DIGITAL-TO-ANALOG MODULATION Process of changing one of the characteristic of an analog signal (typically a sinewave) based on the information in a digital signal. Sinewave is defined by 3 characteristics (amplitude, frequency, and phase) ⇒ digital data (binary 0 & 1) can be represented by varying any of the three.
  • 5. ITRODUCTION ‐QAM  Quadrature Amplitude Modulation or QAM is a form of modulation which is widely used for modulating data signals onto a carrier used for radio communications.  It is widely used because it offers advantages over other forms of data modulation such as PSK, although many forms of data modulation operate along side each other.  Quadrature Amplitude Modulation, QAM is a signal in which two carriers shifted in phase by 90 degrees are modulated and the resultant output consists of both amplitude and phase variations. In view of the fact that both amplitude and phase variations are present it may also be considered as a mixture of amplitude and phase.
  • 7. QAM APPLICATIONS QAM is in many radio communications and data delivery applications. However some specific variants of QAM are used in some specific applications and standards. For domestic broadcast applications for example, 64 QAM and 256 QAM are often used in digital cable television and cable modem applications. In the UK, 16 QAM and 64 QAM are currently used for digital terrestrial television using DVB Digital Video Broadcasting. In the US, 64 QAM and 256 QAM are the mandated modulation schemes for digital cable as standardised by the SCTE in the standard ANSI/SCTE 07 2000. In addition to this, variants of QAM are also used for many wireless and cellular technology applications.
  • 8. ADVANTAGES OF QAM QAM appears to increase the efficiency of transmission for radio. communications systems by utilizing both amplitude and phase variations,
  • 9. DISADVANTAGES OF QAM more susceptible to noise because the states are closer together so that a lower. level of noise is needed to move the signal to a different decision point. Receivers for use with phase or frequency modulation are both able to use limiting amplifiers that are able to remove any amplitude noise and thereby improve the noise reliance. This is not the case with QAM.  The second limitation is also associated with the amplitude component of the signal. When a phase or frequency modulated signal is amplified in a radio transmitter, there is no need to use linear amplifiers, whereas when using QAM that contains an amplitude component, linearity must be maintained. Unfortunately linear amplifiers are less efficient and consume more power, and this makes them less attractive for mobile applications.
  • 10. CONSTELLATION DIAGRAMS FOR QAM Quadrature amplitude modulation, QAM, when used for digital transmission for radio communications applications is able to carry higher data rates than ordinary amplitude modulated schemes and phase modulated schemes. As with phase shift keying, etc, the number of points at which the signal can rest, i.e. the number of points on the constellation is indicated in the modulation format description, e.g. 16QAM uses a 16 point constellation. When using QAM, the constellation points are normally arranged in a square grid with equal vertical and horizontal spacing and as a result the most common forms of QAM use a constellation with the number of points equal to a power of 2 i.e. 2, 4, 8, 16 . . . .
  • 11. By using higher order modulation formats, i.e. more points on the constellation, it is possible to transmit more bits per symbol. However the points are closer together and they are therefore more susceptible to noise and data errors. To provide an example of how QAM operates, the table below provides the bit sequences, and the associated amplitude and phase states. From this it can be seen that a continuous bit stream may be grouped into threes and represented as a sequence of eight permissible states.
  • 12. The constellation diagrams show the different positions for the states within different forms of QAM, quadrature amplitude modulation. As the order of the modulation increases, so does the number of points on the QAM constellation diagram. The diagrams below show constellation diagrams for a variety of formats of modulation:
  • 13. WHY QAM CALLED COMBINED ASK AND PSK Quadrature Amplitude Modulation uses the phase and amplitude of the carrier signal to encode data. QAM finds widespread use in current and emerging wireless standards, including Wi-Fi, Digital Video Broadcast (DVB), WiMAX, IEEE 802.11n, and HSDPA/HSUPA. The QAM modulation scheme encodes data by varying both amplitude and phase of the carrier signal. Thus, it is sometimes viewed as a combination of ASK and PSK modulation. A modulated carrier signal can be expressed in terms of it’s components as: AcCos(2*pi*fc*t+θ) =ICos(2*pi*fc*t) - QSin(2*pi*fc*t) Where I = Ac Cosθ and Ac Sinθ Q=Ac Sinθ
  • 14. Conclusion  Quadrature Amplitude Modulation is an important modulation scheme with many practical applications, including current and future wireless technologies. Some examples of communication systems that use QAM are Wi‐Fi, cable modems, Digital Video Broadcast (DVB) and WiMAX.