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Mini Project- USB Tempera

Mini Project Communication Link Simulation

Digital Modulation TechniquesDigital Modulation TechniquesAuthor: University o !ertordshire

Date created"

Date revised" #$$%

Abstract

The ollo&ing resources come rom the #$$%'($ B)ng *!ons+ in Digital ,ommunications )lectronics*course num.er #)L)$$/0+ rom the

University o !ertordshire1 2ll the mini projects are designed as level t&o modules o the undergraduate programmes1The o.jective o this module is to have .uilt communication lin3s using e4isting 2M modulation5 PS6 modulation and demodulation .loc3s5

constructed 2M modulators and constructed PS6 modulators using operational unction .loc3s .ased on their mathematical e4pressions5 and

conducted simulations o the lin3s and modulators5 all in Simulin371

Use Matla.7' Simulin37 to design a communication lin3 or 2M audio .roadcasting1 The message signal is a mono audio signal although you may

not .e a.le to transmit the ull audio requency range that is normally required or high quality sound1

8n addition to the resources ound .elo& there are supporting documents &hich should .e used in com.ination &ith this resource1 Please see"

Mini Projects - 8ntroductory presentation1Mini Projects - )-Log1

Mini Projects - Sta Student 9uide1

Mini Projects - Standard 9rading ,riteria1

Mini Projects - :election1

;ou &ill also need the


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#

ContentsContents Digital Bandpass ModulationDigital Bandpass Modulation ModulationModulation

Types o modulationTypes o modulation

Digital ModulationDigital Modulation

Digital Modulation ,arrierDigital Modulation ,arrier

@our main modulation techniques@our main modulation techniques

2mplitude Shit 6eying *2S6+2mplitude Shit 6eying *2S6+

@requency Shit 6eying *@S6+@requency Shit 6eying *@S6+ Phase Shit 6eying *PS6+Phase Shit 6eying *PS6+

PS6" Phasor or vector diagrams *constellation diagram+PS6" Phasor or vector diagrams *constellation diagram+

BPS6" Phasor or vector diagram *constellation diagram+BPS6" Phasor or vector diagram *constellation diagram+

Auadrature Phase Shit 6eying *APS6+ - Phasor or vector d111Auadrature Phase Shit 6eying *APS6+ - Phasor or vector d111

M-ary Phase Shit 6eying *MPS6+ - Phasor or vector diagramM-ary Phase Shit 6eying *MPS6+ - Phasor or vector diagram

PS6 9eneral )4pressionPS6 9eneral )4pression

APS6 8mplementationAPS6 8mplementation :elia.ility )iciency:elia.ility )iciency

Spectral eiciency and transmitted po&er trade-oSpectral eiciency and transmitted po&er trade-o

Auadrature 2mplitude Modulation *A2M+Auadrature 2mplitude Modulation *A2M+

:eading list:eading list

,redits,redits


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Digital Bandpass ModulationDigital Bandpass Modulation

Digital modulation techniquesDigital modulation techniques

C 2mplitude Shit 6eying *2S6+2mplitude Shit 6eying *2S6+

C @requency Shit 6eying *@S6+@requency Shit 6eying *@S6+

C Phase Shit 6eying *BPS65 APS6+Phase Shit 6eying *BPS65 APS6+

C Auadrature 2mplitude Modulation *A2M+Auadrature 2mplitude Modulation *A2M+

,omparison &ith regards to",omparison &ith regards to"

C :elia.ility *po&er+5 )iciency *.and&idth+:elia.ility *po&er+5 )iciency *.and&idth+


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0

ModulationModulation

What is modulation?What is modulation?

Modulation is the process by whichModulation is the process by which

message signals are transformed intomessage signals are transformed intohigher frequency waveforms that arehigher frequency waveforms that are

compatible with the characteristics ofcompatible with the characteristics of

the channelthe channel


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Ehy modulateFEhy modulateF

Message signals need to be matched to theMessage signals need to be matched to thecharacteristics of channelscharacteristics of channels

Subsequent advantages of modulation:Subsequent advantages of modulation: Enables efficient economic communicationEnables efficient economic communication

methods to be used as the sharing ofmethods to be used as the sharing ofcommunication resources is made possiblecommunication resources is made possiblesignals can be combined using frequencysignals can be combined using frequency

division multiple!ing " #$M%division multiple!ing " #$M% Efficient antennas of reasonable physical si&e toEfficient antennas of reasonable physical si&e to

be constructed for radio communication systemsbe constructed for radio communication systems


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/

Types o modulationTypes o modulation

2 n a l o g u e M o d u l a t i o n D i g i t a l M o d u l a t i o n

M o d u l a t i o n


techniques fortechniques for

analogue signalsanalogue signals


techniques fortechniques for

digital signalsdigital signals


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G

Digital ModulationDigital Modulation

$igital modulation is the process by$igital modulation is the process bywhich digital symbols are transformedwhich digital symbols are transformedinto waveforms that are compatibleinto waveforms that are compatiblewith the characteristics of the channelwith the characteristics of the channel

'o carry out digital modulation( we'o carry out digital modulation( weneed:need:

) digital) digital messagemessageoror informationinformationorormodulatingmodulatingsignal( andsignal( and

) sinusoid) sinusoid carrier wavecarrier waveor simply aor simply acarriercarrier

*+,+: 'he carrier is always of much higher*+,+: 'he carrier is always of much higherfrequency than the modulating signalfrequency than the modulating signal


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H

Digital Modulation - ,arrierDigital Modulation - ,arrier

-eneral form of the carrier wave is-eneral form of the carrier wave is

wherewhere

))cc. amplitude in volts /%. amplitude in volts /%

cc. angular or radian frequency in rads. angular or radian frequency in rads"0"0

cc. phase in radian rad%. phase in radian rad%

)lternatively( since)lternatively( since

wherewhere ffcc. frequency in hert& 1&%. frequency in hert& 1&%

)cos()( ccc tAtc +=

)2cos()( ccc tfAtc +=

f 2=


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%

Digital Modulation - ,arrierDigital Modulation - ,arrier

)2cos()cos()( cccccc tfAtAtc +=+=

seconds1

carrier,theofperiodThec

cf

T =

2)

")

'c

t

ct%

3n digital modulation( one of the properties of the3n digital modulation( one of the properties of the

carrier amplitude( frequency or phase% is changedcarrier amplitude( frequency or phase% is changed

according to the modulating or information oraccording to the modulating or information or

message% signalmessage% signal


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($

@our main modulation techniques@our main modulation techniques

2 m p l i t u d eS h i t 6 e y i n g

2 S 6

@ r e q u e n c yS h i t 6 e y i n g

@ S 6

P h a s eS h i t 6 e y i n g

P S 6

A u a d r a t u r e2 m p l i t u d e

M o d u l a t i o n * A 2 M +

D i g i t a l M o d u l a t i o n

ChangingChanging

amplitudeamplitude

))cc% of carrier% of carrier

according toaccording tomodulatingmodulating

signalsignal

ChangingChanging

phase phase cc% of% of

carriercarrier


signalsignal

ChangingChanging

frequencyfrequency

ffcc% of carrier% of carrier


signalsignal

CombinationCombination

of )S4 andof )S4 and

5S45S4


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((

2mplitude Shit 6eying *2S6+2mplitude Shit 6eying *2S6+

mt%: modulating signal baseband signal%mt%: modulating signal baseband signal%ct%: carrier wave high frequency cosine%ct%: carrier wave high frequency cosine%

yt%: modulated signal 6 )S4 signalyt%: modulated signal 6 )S4 signal

bandpass signal%bandpass signal%

mt%mt% yt%yt%

ct%ct%

)()()( tctmty =

)S4 modulator can be)S4 modulator can be

represented by therepresented by the

schematic diagram onschematic diagram onthe rightthe right

)S4)S4 amplitude of carrier is changedamplitude of carrier is changed

according to the modulating signalaccording to the modulating signal


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(#

2mplitude Shit 6eying *2S6+ ctdI2mplitude Shit 6eying *2S6+ ctdI

,inary )S4 also called on"off 7eying 884%,inary )S4 also called on"off 7eying 884%

00 99 99 00 99 00 00 99

3nformation3nformation

or messageor message

or basebandor baseband

datadata

Carrier waveCarrier wave

or carrieror carrier

$ata stream:$ata stream:

884 waveform884 waveform

bandpassbandpass

signal%signal%


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(

@requency Shit 6eying *@S6+@requency Shit 6eying *@S6+

#S4#S4 frequency of carrier is changedfrequency of carrier is changedaccording to modulating signalaccording to modulating signal

,inary #S4 ,#S4% represents ones,inary #S4 ,#S4% represents onesand &eros by carrier pulses of twoand &eros by carrier pulses of two

distinct frequencies( fdistinct frequencies( f00and fand f::

,inary &ero,inary &ero frequency ffrequency f00,inary one,inary one frequency ffrequency f::


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(0

@requency Shit 6eying *@S6+ ctdI@requency Shit 6eying *@S6+ ctdI

00 99 99 00 99 00 00 993nformation3nformation



datadata




,#S4 waveform,#S4 waveform

bandpassbandpass

signal%signal%


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(

@requency Shit 6eying *@S6+ ctdI@requency Shit 6eying *@S6+ ctdI

,#S4 signal can be,#S4 signal can beconsidered as theconsidered as thecombination of two 884combination of two 884signals:signals:

0%0%

8ne representing the8ne representing thebaseband data streambaseband data stream;mt%


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(/

Phase Shit 6eying *PS6+Phase Shit 6eying *PS6+

5S45S4 phase of carrier is changedphase of carrier is changed

according to modulating signalaccording to modulating signal


2)

")

'c

t

ct%

8ne period('c

Equivalent to a completeturn phase angle

0 complete turn phaseangle . rad .>9%


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(G

Phase Shit 6eying *PS6+ ctdIPhase Shit 6eying *PS6+ ctdIc. 9 rad .9%

c. rad .0@9%

t

t

ct%

ct2 %

t

t

c. >A rad .B9%

c. A rad .9%

ct2 >A%

ct2 A%


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(H

Phase Shit 6eying *PS6+ ctdIPhase Shit 6eying *PS6+ ctdI


,inary 5S4 ,5S4% represents ones,inary 5S4 ,5S4% represents ones

and &eros by shifting the phase byand &eros by shifting the phase by 00

andand

,inary &ero,inary &ero phasephase 00 9 rad or 99 rad or 9%%

,inary one,inary one phasephase rad or 0@9rad or 0@9%%

5S45S4 phase of carrier is changedphase of carrier is changedaccording to modulating signalaccording to modulating signal


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(%

Phase Shit 6eying *PS6+ ctdIPhase Shit 6eying *PS6+ ctdI

00 99 99 00 99 00 00 993nformation3nformation



datadata




,5S4 waveform,5S4 waveform

bandpassbandpass

signal%signal%

PS6 Ph di


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#$

PS6" Phasor or vector diagramsPS6" Phasor or vector diagrams

*constellation diagram+*constellation diagram+

.9 rad .9

. rad .>9

.A rad.9

.rad

.0@9

.>A rad

.B9


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#(

BPS6" Phasor or vector diagramBPS6" Phasor or vector diagram

*constellation diagram+*constellation diagram+

.9

.A

.

.>A

m0m

,inary: two possible states m,inary: two possible states m00and mand m

$ecision region 0$ecision region 0$ecision region $ecision region

$ecision boundary$ecision boundary

EuclideanEuclidean

distance: distancedistance: distance

between twobetween two

message pointsmessage points

A d Ph Shi 6 i


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##

Auadrature Phase Shit 6eyingAuadrature Phase Shit 6eying

*APS6+ - Phasor or vector diagram*APS6+ - Phasor or vector diagram

.9

.A

.

.>A

m0

m

Duadrature: four possible states mDuadrature: four possible states m00( m( m(m(m>>and mand m

m

m>

$ecision region 0$ecision region 0

$ecision region $ecision region

$ecision region >$ecision region >

$ecision region $ecision region



M Ph Shit 6 i *MPS6+


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#

M-ary Phase Shit 6eying *MPS6+ -M-ary Phase Shit 6eying *MPS6+ -

Phasor or vector diagramPhasor or vector diagram

.9

.A

.

.>A

m0

m>

M"ary: M possible states mM"ary: M possible states m00( m( m( m( m>>( F m( F mMM

mB

mG

m@m

m m

Hegion 0Hegion 0

Hegion @Hegion @

Hegion Hegion Hegion Hegion

Hegion BHegion B

Hegion >Hegion >

Hegion GHegion G

Hegion Hegion

SignalSignal

constellationconstellation

for @"5S4for @"5S4


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#0

PSK General ExpressionPSK General Expression

'he general analytic e!pression of 5S4 is more'he general analytic e!pression of 5S4 is more

popularly written aspopularly written as

E is the symbol energy and ' is the information signal=s symbolE is the symbol energy and ' is the information signal=s symbol

time duration+ i.0( ( ++M+time duration+ i.0( ( ++M+

5hase term5hase term iit%t%has M discrete values given byhas M discrete values given by

,5S4( M.I D5S4( M.I @"5S4( M.@I etc,5S4( M.I D5S4( M.I @"5S4( M.@I etc

( )

Mit

ttT

E

tm

i

ici

2)(

)(cos

2

)(

=

+=


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#

PSK CodinPSK Codin

,5S4: each state m0( m% is,5S4: each state m0( m% isrepresented by one digit 9( 0%represented by one digit 9( 0%

D5S4: each state m0( m( m>( m%D5S4: each state m0( m( m>( m%

is represented by two digits 99( 90(is represented by two digits 99( 90(09( 00%09( 00%

@5S4: each state is presented by@5S4: each state is presented by

three digits 999( 990( 909( 900(three digits 999( 990( 909( 900(099( 090( 009( 000%099( 090( 009( 000% EtcFEtcF


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#/

!PSK "mplementation!PSK "mplementation

,y e!panding the general e!pression( D5S4 can be,y e!panding the general e!pression( D5S4 can beimplemented in the following way+implemented in the following way+

3n D5S4 the information bit stream is divided to form3n D5S4 the information bit stream is divided to formtwo streams( in"phase 3% and in quadrature D%(two streams( in"phase 3% and in quadrature D%(comprising of the even and odd bits of the originalcomprising of the even and odd bits of the original

information signal respectivelyinformation signal respectively Since each transmitted symbol is represented by twoSince each transmitted symbol is represented by two

successive binary pulses( the symbol rate of the 3 andsuccessive binary pulses( the symbol rate of the 3 andD waveforms is half the bit rate of the informationD waveforms is half the bit rate of the informationsignal signal Rs=RbRs=RbAlogAlog::M%+M%+

Subsequently the bipolar 3 and D streams are used toSubsequently the bipolar 3 and D streams are used tomodulate the components of a carrier frequency inmodulate the components of a carrier frequency inquadraturequadrature Modulation of each orthogonal carrier follows a $S,"SC")MModulation of each orthogonal carrier follows a $S,"SC")M

mode resulting in two ,5S4 signalsmode resulting in two ,5S4 signals


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#G

!PSK Circuit Diaram!PSK Circuit Diaram 'wo carriers are inphase quadrature+'wo carriers are inphase quadrature+

3n the case of the inphase data stream( the phase of the cosine carrier is3n the case of the inphase data stream( the phase of the cosine carrier isshifted( at symbol transitions( between 9shifted( at symbol transitions( between 9ooand 0@9and 0@9oo

Equivalently the quadrature data stream shifts the phase of the sineEquivalently the quadrature data stream shifts the phase of the sinefunction between 9function between 9ooand B9and B9oo

'he modulated signals are combined linearly to produce the D5S4'he modulated signals are combined linearly to produce the D5S4waveformwaveform JJt%.t%.99oo( 9( 9oo( 0@9( 0@9ooand B9and B9oo


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#H

:elia.ility )iciency:elia.ility )iciency

Heliability of scheme: how li7ely areHeliability of scheme: how li7ely areerrorsI this is related to theerrorsI this is related to theEuclidean distanceEuclidean distance

E!pressed by the ,EH versus S*HE!pressed by the ,EH versus S*HEbA*o%: What is the probability ofEbA*o%: What is the probability oferror?error?

Efficiency: measure of the data rateEfficiency: measure of the data rateE!pressed by the number of bits perE!pressed by the number of bits persymbolsymbol


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#%

:elia.ility )iciency ctdI:elia.ility )iciency ctdI

)s M increases( the Euclidean)s M increases( the Euclideandistance decreasesdistance decreases

1ence( the probability of error1ence( the probability of error

increasesI therefore the reliabilityincreasesI therefore the reliabilitydecreasesdecreases

)s M increases( data rate increases)s M increases( data rate increases

1ence the efficiency increases1ence the efficiency increases 'rade"off between reliability and'rade"off between reliability and

efficiency to be consideredefficiency to be considered


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$

Spectral e##icienc$ andSpectral e##icienc$ and

transmitted po%er trade&o##transmitted po%er trade&o## #or the same system bandwidth a#or the same system bandwidth a

quadrature modulation scheme canquadrature modulation scheme can

transmit twice the data rate achievabletransmit twice the data rate achievable

with its binary counterpartwith its binary counterpart 'he superior performance of'he superior performance of MM"level"level

signaling by means of higher achievablesignaling by means of higher achievable

transmission rates for a given channeltransmission rates for a given channel

bandwidth is achieved in the e!pense ofbandwidth is achieved in the e!pense ofincreased transmitted power better S*H%increased transmitted power better S*H%

for a required reliability ,EH%+for a required reliability ,EH%+

A d t 2 lit d M d l tiA adrat re 2mplit de Mod lation


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(

Auadrature 2mplitude ModulationAuadrature 2mplitude Modulation

*A2M+*A2M+

)lso 7nown as )mplitude 5hase)lso 7nown as )mplitude 5hase

4eying )54%4eying )54%

Combination of )S4 and 5S4Combination of )S4 and 5S4

@"D)M@"D)M

0"D)M0"D)M


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#

:eading list:eading list

S7lar( ,+( 990%( K$igitalS7lar( ,+( 990%( K$igital

Communications: #undamentals andCommunications: #undamentals and

)pplicationsL( 5rentice 1all( )pplicationsL( 5rentice 1all( ndnd

Edition: sections +0 6 +Edition: sections +0 6 + -lover( 3+) -rant 5+M+( 99%(-lover( 3+) -rant 5+M+( 99%(

$igital CommunicationsL( 5earson$igital CommunicationsL( 5earson

5rentice 1all( 5rentice 1all( ndndEdition: sectionsEdition: sections00+0 6 00+>00+0 6 00+>


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This resource &as created .y the University o !ertordshire and released as an open educational resource through the Jpen )ngineering:esources project o the !) 2cademy )ngineering Su.ject ,entre1 The Jpen )ngineering :esources project &as unded .y !)@,) and part

o the K8S,'!) 2cademy U6J): programme1

? University o !ertordshire #$$%

This &or3 is licensed under a ,reative ,ommons 2ttri.ution #1$ License1

The name o the University o !ertordshire5 U! and the U! logo are the name and registered mar3s o the University o !ertordshire1 To the ullest e4tent permitted .y la& theUniversity o !ertordshire reserves all its rights in its name and mar3s &hich may not .e used e4cept &ith its &ritten permission1

The K8S, logo is licensed under the terms o the ,reative ,ommons 2ttri.ution->on-,ommercial->o Derivative Eor3s #1$ U6" )ngland Eales Licence1 2ll reproductions must

comply &ith the terms o that licence1

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