pulse modulationtech

8/9/2019 Pulse Modulationtech

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Presented by

Se elex students

Pvppcoe


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TYPES OF PULSE

MODULATION


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Pulse Amplitude Modulation

Pulse-amplitude modulation a!ronym PAM is a "orm

o" si#nal modulation$%ere t%e messa#e in"ormation is

en!oded in t%e amplitudeo" a series o" si#nal pulses&

E'ample( A t$o)bit modulator *PAM)+, $ill ta-e t$o bits

at a time and $ill map t%e si#nal amplitude to one o" "our

possible le.els "or e'ample /0 .olts /1 .olt 1 .olt and

0 .olts&

Demodulation is per"ormed by dete!tin# t%e amplitude

le.el o" t%e !arrier at e.ery symbol period&
http://en.wikipedia.org/wiki/Modulationhttp://en.wikipedia.org/wiki/Amplitudehttp://en.wikipedia.org/wiki/Amplitudehttp://en.wikipedia.org/wiki/Modulation


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Types O" PAM

T%ere are t$o types o" pulse amplitude modulation(

1&Sin#le polarity PAM( In t%is a suitable "i'ed d! le.el isadded to t%e si#nal to ensure t%at all t%e pulses arepositi.e #oin#&

2&Double polarity PAM( In t%is t%e pulses are bot%positi.e and ne#ati.e #oin#&

Pulse)amplitude modulation is $idely used in baseband

transmission o" di#ital data $it% non)basebandappli!ations %a.in# been lar#ely repla!ed bypulse)!ode modulation and more re!ently bypulse)position modulation&
http://en.wikipedia.org/wiki/Basebandhttp://en.wikipedia.org/wiki/Pulse-code_modulationhttp://en.wikipedia.org/wiki/Pulse-position_modulationhttp://en.wikipedia.org/wiki/Pulse-position_modulationhttp://en.wikipedia.org/wiki/Pulse-code_modulationhttp://en.wikipedia.org/wiki/Baseband


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Use in Ethernet

Some .ersions o" t%e Et%ernet!ommuni!ation standardare an e'ample o" PAM usa#e&

In parti!ular t%e Fast Et%ernet1334ASE)T2 medium*no$ de"un!t, runnin# at 133 Mbit5s uses "i.e)le.el PAM

modulation *PAM)6, runnin# at 26 me#apulses5se! o.ert$o $ire pairs& A spe!ial te!%ni7ue is used to redu!e inter)symbol

inter"eren!e bet$een t%e uns%ielded pairs&8citation needed9&

Later t%e #i#abit Et%ernet13334ASE)T medium raisedt%e bar to use "our pairs o" $ire runnin# ea!% at 126me#apulses5se! to a!%ie.e 1333 Mbit5s data rates stillutili:in# PAM)6 "or ea!% pair&
http://en.wikipedia.org/wiki/Ethernethttp://en.wikipedia.org/wiki/Fast_Ethernethttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Gigabit_Ethernethttp://en.wikipedia.org/wiki/Gigabit_Ethernethttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Fast_Ethernethttp://en.wikipedia.org/wiki/Ethernet


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Use in photobiology

T%e !on!ept is also used "or t%e study o" p%otosynt%esis

usin# a PAM "luorometer&

T%is spe!iali:ed instrument in.ol.es aspe!tro"luorometri!measurement o" t%e -ineti!s o"

"luores!en!e rise and de!ay in t%e li#%t)%ar.estin#

antenna o" t%yla-oidmembranes t%us 7ueryin# .arious

aspe!ts o" t%e state o" t%e p%otosystems under di""erent

en.ironmental !onditions&
http://en.wikipedia.org/wiki/Photosynthesishttp://en.wikipedia.org/w/index.php?title=Pulse-amplitude_modulation_fluorometry&action=edit&redlink=1http://en.wikipedia.org/wiki/Fluorescence_spectroscopyhttp://en.wikipedia.org/wiki/Thylakoidhttp://en.wikipedia.org/wiki/Thylakoidhttp://en.wikipedia.org/wiki/Fluorescence_spectroscopyhttp://en.wikipedia.org/w/index.php?title=Pulse-amplitude_modulation_fluorometry&action=edit&redlink=1http://en.wikipedia.org/wiki/Photosynthesis


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Use in electronic drivers for LED

lighting

Pulse)amplitude modulation %as also been de.eloped "or t%e!ontrol o" li#%t)emittin# diodes *LEDs, espe!ially "or li#%tin#appli!ations&

LED dri.ers based on t%e PAM te!%ni7ue o""er impro.edener#y e""i!ien!y o.er systems based upon ot%er !ommondri.er modulation te!%ni7ues su!% as pulse)$idt% modulation*P;M, as t%e "or$ard !urrent passin# t%rou#% an LED isrelati.e to t%e intensity o" t%e li#%t output and t%e LEDe""i!ien!y in!reases as t%e "or$ard !urrent is redu!ed&

Pulse)amplitude modulation LED dri.ers are able to

syn!%roni:e pulses a!ross multiple LED !%annels to enableper"e!t !olour mat!%in#& Due to t%e in%erent nature o" PAMin !on


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Pulse ;idt% Modulation

Pulse-width modulation (PM! or pulse-duration

modulation (PDM! is a !ommonly used te!%ni7ue "or

!ontrollin# po$er to inertial ele!tri!al de.i!es made

pra!ti!al by modern ele!troni! po$er s$it!%es&

T%e P;M s$it!%in# "re7uen!y %as to be mu!% "aster t%an$%at $ould a""e!t t%e load $%i!% is to say t%e de.i!e t%at

uses t%e po$er&

T%e main ad.anta#e o" P;M is t%at po$er loss in t%e

s$it!%in# de.i!es is .ery lo$& P;M %as also been used in !ertain !ommuni!ation systems

$%ere its duty !y!le %as been used to !on.ey in"ormation

o.er a !ommuni!ations !%annel&
http://en.wikipedia.org/wiki/Signalling_%28telecommunication%29http://en.wikipedia.org/wiki/Signalling_%28telecommunication%29


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Types o" P;M

T%ree types o" pulse)$idt% modulation *P;M, are

possible(

T%e pulse !enter may be "i'ed in t%e !enter o" t%e time

$indo$ and bot% ed#eso" t%e pulse mo.ed to !ompress

or e'pand t%e $idt%&

T%e lead ed#e !an be %eld at t%e lead ed#e o" t%e

$indo$ and t%e tail ed#e modulated&

T%e tail ed#e !an be "i'ed and t%e lead ed#e modulated&
http://en.wikipedia.org/wiki/Signal_edgehttp://en.wikipedia.org/wiki/Signal_edge


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Principle

Pulse)$idt% modulation uses are!tan#ular pulse $a.e$%osepulse $idt% is modulated resultin#in t%e .ariation o" t%e a.era#e.alue o" t%e $a.e"orm&

T%e simplest $ay to #enerate aP;M si#nal is t%e interse!ti.emet%od $%i!% re7uires only asa$toot%or a trian#le$a.e"orm*easily #enerated usin# a simpleos!illator, and a !omparator

;%en t%e .alue o" t%e re"eren!esi#nal *t%e red sine $a.e in "i#ure2, is more t%an t%e modulation$a.e"orm *blue, t%e P;M si#nal*ma#enta, is in t%e %i#% stateot%er$ise it is in t%e lo$ state&
http://en.wikipedia.org/w/index.php?title=Rectangular_pulse_wave&action=edit&redlink=1http://en.wikipedia.org/wiki/Averagehttp://en.wikipedia.org/wiki/Sawtooth_wavehttp://en.wikipedia.org/wiki/Triangle_wavehttp://en.wikipedia.org/wiki/Electronic_oscillatorhttp://en.wikipedia.org/wiki/Comparatorhttp://en.wikipedia.org/wiki/Comparatorhttp://en.wikipedia.org/wiki/Electronic_oscillatorhttp://en.wikipedia.org/wiki/Triangle_wavehttp://en.wikipedia.org/wiki/Sawtooth_wavehttp://en.wikipedia.org/wiki/Averagehttp://en.wikipedia.org/w/index.php?title=Rectangular_pulse_wave&action=edit&redlink=1


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Applications


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"elecommunications

In tele!ommuni!ations t%e $idt%s o" t%e pulses!orrespond to spe!i"i! data .alues en!oded atone end and de!oded at t%e ot%er&

Pulses o" .arious len#t%s *t%e in"ormation itsel",$ill be sent at re#ular inter.als *t%e!arrier "re7uen!yo" t%e modulation,&

T%e in!lusion o" a !lo!- si#nalis not ne!essary

as t%e leadin# ed#e o" t%e data si#nal !an beused as t%e !lo!- i" a small o""set is added to t%edata .alue in order to a.oid a data .alue $it% a:ero len#t% pulse&
http://en.wikipedia.org/wiki/Telecommunicationshttp://en.wikipedia.org/wiki/Carrier_wavehttp://en.wikipedia.org/wiki/Clock_signalhttp://en.wikipedia.org/wiki/Clock_signalhttp://en.wikipedia.org/wiki/Carrier_wavehttp://en.wikipedia.org/wiki/Telecommunications


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Power delivery

P;M !an be used to !ontrol t%e amount o" po$erdeli.ered to a load $it%out in!urrin# t%e losses t%at$ould result "rom linear po$er deli.ery by resisti.emeans&

Potential dra$ba!-s to t%is te!%ni7ue are t%e pulsationsde"ined by t%e duty !y!le s$it!%in# "re7uen!y andproperties o" t%e load&

;it% a su""i!iently %i#% s$it!%in# "re7uen!y and $%enne!essary usin# additional passi.e ele!troni! "ilters t%epulse train !an be smoot%ed and a.era#e analo#$a.e"orm re!o.ered&
http://en.wikipedia.org/wiki/Electronic_filterhttp://en.wikipedia.org/wiki/Electronic_filter


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#oltage regulation

P;M is also used in e""i!ient .olta#e re#ulators&

4y s$it!%in# .olta#e to t%e load $it% t%e appropriate duty!y!le t%e output $ill appro'imate a .olta#e at t%edesired le.el& T%e s$it!%in# noise is usually "iltered $it%an indu!torand a !apa!itor& ne met%od measures t%eoutput .olta#e&

;%en it is lo$er t%an t%e desired .olta#e it turns on t%es$it!%& ;%en t%e output .olta#e is abo.e t%e desired.olta#e it turns o"" t%e s$it!%&
http://en.wikipedia.org/wiki/Voltage_regulatorhttp://en.wikipedia.org/wiki/Inductorhttp://en.wikipedia.org/wiki/Capacitorhttp://en.wikipedia.org/wiki/Capacitorhttp://en.wikipedia.org/wiki/Inductorhttp://en.wikipedia.org/wiki/Voltage_regulator


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Audio effects and amplification

P;M is sometimes used in sound *musi!, synt%esis in

parti!ular subtra!ti.e synt%esis as it #i.es a sound e""e!t

similar to !%orus or sli#%tly detuned os!illators played

to#et%er&

%e ratio bet$een t%e %i#% and lo$ le.el is typi!ally

modulated $it% a lo$ "re7uen!y os!illator or LFO&

In addition .aryin# t%e duty !y!le o" a pulse $a.e"orm in

a subtra!ti.e)synt%esis instrument !reates use"ul timbral

.ariations&

A li ti f $%
http://en.wikipedia.org/wiki/Subtractive_synthesishttp://en.wikipedia.org/wiki/Low_frequency_oscillationhttp://en.wikipedia.org/wiki/Low_frequency_oscillationhttp://en.wikipedia.org/wiki/Subtractive_synthesis


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Applications for $%

communications

Narro$band =F *radio "re7uen!y, !%annels $it% lo$po$er and lon# $a.elen#t%s *i&e& lo$ "re7uen!y, area""e!ted primarily by "lat "adin# and PPM is better suitedt%an M)FS> to be used in t%ese s!enarios&

One !ommon appli!ation $it% t%ese !%annel!%ara!teristi!s "irst used in t%e early 1?@3s is t%e radio!ontrol o" model air!ra"t boats and !ars&

PPM is employed in t%ese systems $it% t%e position o"ea!% pulse representin# t%e an#ular position o" ananalo#ue !ontrol on t%e transmitter or possible states o"a binary s$it!%&
http://en.wikipedia.org/wiki/Fadinghttp://en.wikipedia.org/wiki/Fading


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T%e number o" pulses per "rame #i.es t%e number o"!ontrollable !%annels a.ailable&

T%e ad.anta#e o" usin# PPM "or t%is type o" appli!ation

is t%at t%e ele!troni!s re7uired to de!ode t%e si#nal aree'tremely simple $%i!% leads to small li#%t)$ei#%tre!ei.er5de!oder units&

Ser.os made "or model radio !ontrol in!lude some o"

t%e ele!troni!s re7uired to !on.ert t%e pulse to t%e motorposition t%e re!ei.er is merely re7uired to demultiple't%e separate !%annels and "eed t%e pulses to ea!%ser.o&


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More sop%isti!ated =5B systems are no$ o"ten based onpulse)!ode modulation $%i!% is more !omple' but o""ers#reater "le'ibility and reliability&

Pulse position modulation is also used "or!ommuni!ation to t%e ISO5IEB 16@?0 !onta!tless smart!ard as $ell as t%e CF implementation o" t%e EPB Blass

1 proto!ol "or =FID ta#s&


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Pulse Position Modulation

Pulse-position modulation*PPM, is a "orm o" si#nalmodulation in $%i!% M messa#e bits are en!oded bytransmittin# a sin#le pulse in one o" possible time)s%i"ts

One o" t%e -ey di""i!ulties o" implementin# t%is te!%ni7ue ist%at t%e re!ei.er must be properly syn!%roni:ed to ali#n t%elo!al !lo!- $it% t%e be#innin# o" ea!% symbol& T%ere"ore itis o"ten implemented di""erentially as differential pulse-

position modulation $%ereby ea!% pulse position isen!oded relati.e to t%e pre.ious su!% t%at t%e re!ei.ermust only measure t%e di""eren!e in t%e arri.al time o"

su!!essi.e pulses& It is possible to limit t%e propa#ation o" errors to ad


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Illustration o" PAM P;M and PPM

*a, is input *in"ormation, si#nal


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Time di.ision multiple'in# o" t$o

PAM si#nals


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E""e!ts o" noise on pulses*a, e""e!t on PAM only "or ideal pulses

*b, e""e!t on P;M PPM "or pra!ti!alpulses

a ura samp n# n an


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a ura samp n# n ) an )domains

a oppe samp n# n an


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a oppe samp n# n ) an )domains


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A de"inition o" baseband and

bandpass si#nals


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=elations%ip

bet$een PAM7uantised PAM

and PBM

si#nals


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Input5output SN= "or PBM


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Delta PBM transmitter and

re!ei.er


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uantisation error interpreted

as noise i&e& gq(t) = g(t) + q(t)


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