Unit3

Tdeal Smping
Palse tmplitude Modulation
Width
Pulse
Plse position
Quantizaticn
Analag Rutse tonsrnissicn
Communicaion Digital
Communicaton
Techinue Paralle! &serial
transmission
Data corNersion

Patse code Modulation

Delta Modulation

Jtoduetion:
Continuus oave modutatien, the cames
t In towever, in pulse modulaticn
nature.
be continuous in time stgnals
to repe Sent
discrete
we have to use modulated wave
tmodulated Signal d pulse

contiraous signal

biscrcte tirme aonal

Convert cortinuous tne
to
Sampíng psocess is used
Shnal into disore te time signa
Somping Pccess
 ajuialent discete tine snat
te an by sapling signal
.Sittth pes'ton is conthollk
tain ulses a tunit
Sänling snal is a piode
tine s is knon as
id Is th
amplitude $
ths tin
suiteh is clase d, 50 the samped
-gtime / duning ainat
is equat the iput
te (fen 6 ne iput signat
signa suitth is
* Duning emaining tme
appean at op
Cntinueus amyled

ntíurs signa
signal)

Cauníey signal)
Angled aignal
(modutated

Gng the lem:

Sampine
A Sampling theovem states that,
A Contuous time comletely vep1escrted
aígna con ke the Sampling eq
its Samples & ecOeYcd back if
m
’mu fres presented in sgna
Palse Modulation -
oidth 4 pastion)¢a
panametess (Amplitude, instantoncous
* Seme the
Varied accovding to modulation
pulse toan is modulating signal, then this
value d the "pulse modulaticn
as
can be ieened
c puse modulation:
ypes M systems
types of
4 There he two modulation
tude
|. PAM - pulse ampli modulation
PTM- pulse time
&.
positon modulaton
PPM e) pulse
PuM
pulse dth vasfed
modulation
canes palse train
fs
the amplitude 4 modulatid'sipal
* In PAM, amplitude d the
accovdance with the position) o the Caies
in width Ds the, modulating
PTN, the
tne dance uYth amplitude
# Ih accor
tian & Varied in Var?.J
pulse pulse traín is
the camier modulabing
the
PWM, the width ampitude
In with the
accodance
in pulse. train &vail
signal the position the carsierthe modulating
4 In
PPM,
the
amplitude
accordarnce with
in
Amplitude Modalaton- tine Each son
Pulse intewal d
taken at egula deterrmíned by annpítud
+ Sompes ase amplitude is
sGmole s
pulse, whose uwhich the
instort time at
Vuiable at the
 message signa
t

modutated

approximgton
aeasonable
axe taken, a Constructed at the
+I enough Samples
sampied Can beputse Amplitude modulat
the signal being kroun as
q
veceiving end
This is

-ion".
PAM-> demo dulate PAM switch,
Genevotion genercate & thaough
Very easy to to PAM is ted
* It is to be conveste.dpulse tran level, the
Signal lled by a high
* ontso Signatis at
which is present ie,
tevel,the uoiteh
When pulse is Signal is at tow
* tch is closed.
Soi absent i.e, PAM waVefosm
pulse is get
* When soitch,we
is cpen control actiorn
thís Soitch netwok,
4 With terminal pulse shaping
at olp passed thacugh olp pulses can be
Thís PAM is Flat tops These
whích gives thern modulate the caries to torm
PAM-FM

used to trequency

Pulse
Ghaping

puse tran.
 Block diagram PAM Genwation -’ D
S

modula Soplig PAM

sgral Palse
train
geneator

* It consists LPF, a
gerenata
multipiexen palse tranremoves
-thyough (pr.he (PF l
+ Initially nlt) is passed
hahe thon tn Thís is
trequeny Components chích axc
knoun as Band tmiting
Boand lonitr s necess ay to avoid the "Alasing fectf
* The
in Sarmping process pulse ain at a
generat genenates a
+ The pulse traín 2 atn Ths the Nyguist citeia
tquency ts' such that ts netuok does the Shaping
is satistad. The pulsetops
Samping
tooxk to give tat
m(t)

t puse tan

Natuna
PAM

’t Flat top
PAM
 Depo dul ation PAM Reconstuctien cf Original
Demodulation
LPE o PAM
PAM,
signal Can be o btaired by passing PAM
+Tthe coiginal ognal LPF Temoves
signal thrcugh
trequency is tued to tm Then
the oiginal
LPF recovers
+ The are above
"tm'.,
frequencies chich the
modulating signat SÍgna!
at
detectionlp
PAM

Demodulatd
output

case ¢ {lat top PAM to educe " Apertuse

+ In used.
a n equalizey is
ettect,
PAM
Sianc
st)+Abise
JReconstuetioraualee
ilte

Conpanison Samplng chniques q PAM -»

SNO asarneten |Natuwal sanpling | Flat top Sampling
It uses Chopping t uses Sample& hold
|Principlk principle eircuit
Sarmplng Suitch D'schaesotch
R
st)
Somplo
S.No panometes Natural sompling Flat top anplng
3 Wae fors

This method is This method is ued

Use
used proctically poctically
It satises citeia
6 Somplng ote t satisfes
iteia
Maximum
Noise Minimum
Intererence
s)- x(nt) H{t -nt)
Eme Domain s)TA alt)
Representation sirclh)ej anost

Frea
domain s). TA sinc( st)" ts 2
Repsesertation Ts n
<(4-nts)

process
Geneation demodulation PAM IS a simple
cicuits.
both k Rx
Construction
Demexits PAM 8 vaviations, So noise ebet s noe
armplitude pulse having
PAM produces handle the
move powe to
uises
3 he T* teq
max
amplitude.
PAM baued on Shna pdaity’
classitication
be classiicd into a types
Can
4 PA N
Single polaity PAM
Doube polaity PAM is added to
6 de level
h this, oa fixed
modulated olp it,
single polarity PAM
x), Such that
the
the modulating signa
 Gingleplauity
PAM

abe pooanity PAM:

Double polorty PAM

Applications PAM-»
cornrounication Ciscuts
Cthernet tos LED
Uaed in deiver
electonic
Acts as
Used in photo biolegt techniue in ovder to
aerevate
Controllers Use this
4 Mico
control
Modulation classified into too
alse hlidth rnodulation, Can be
he palie tine ) duvotion modulotion
width
modulation
tyes position heldconsa
J putse pule is
rodulatior, amplitude pulse is made ar
Ir pule tine or uwitthd
4 position o pule
-nt, wherc as, arnplitude the siana
the
.tional toPIM, is Vavied in accondarce
the width pulse
Signal palse duxoton modalation:
oith the ne Ssag
as
PhiM is also alled
ons, 3 Vamiations o, PhM ase possib
+ In PttM A
 t leading cdg
a Centhe cdge
3 -Ta:l edg
teading-os, ail edge
edge

Att modulang

leading (a)

Toil ed ge
certre
e
at its tve peak at point ()G
The modulating sgnal is
* 8
its -ve peak at
is kept constort &pulse th, s
Leading edg,i- It lead edge.
measuved fuom themoe at point 'A'
pulse width is minimum at point'8
* is
pulse width
Generation Pam sgnal
Modulasng
x()
Sowtooth
qenesatoy
Cormpanator
Sauwtooth qenerafor moduloti
It consists ot compares the amplttude
1he com pavotor
+
 AWM ol

as long asthe
comparator is high acotoott
the etes thon the
the olo Values xlt) s vemains high
instantancous comparator olp signat
the modulaHng
Sijnat.duration tor ohichamplitude the
he poportionalto op is PwM signal
s divectly
sesult the
comparator
As a ciscuit:
2enoator
PWM
R

6
molulafing signal
5
a
5
muttivibratoy oith
monostable votage
basitally contzcllkd
* It 6 ilp signat pplicdvoltage at the agjusted to td Vec3

modulating 1s valtoy
contiolled
Intesnally the modulating sgna changes the cortvol
+ applied voltage level
frternally
+ hence the threshold capacitoy upto
6 vequíed to chare the
nesalt time PhiM Signal a olp.
4 As a level chonges
gives
thyehold eltog

t
 se id,
nodulated
diagam menostahk mulivib1oh
* Jntenal ckt
PUM
-thg

Ro

state tor above circuit Ta- OFF, T,-ON

* the Stable 8, suitches ToN De to
The vc aoing triggeing
pulse. at draw the collkct
nouo begins to
this woltoge at talls as T,
voltage at, B also tals 5 is Guithe
Cunent aised o chágg
4 As a vesult, Ete upto the collectoy Suppy votage 'ee
CFF. ' ' begins to charge
through 'e the supply toltage &'R tire
time deterincd by
# A<ter a nl the base of T, becones suficie
constant ¢ the changing ON
4ue' to Suoitch T
-ntby , 6 suitched OFF by egernerotiue action §
4 The tansistos aival the next triggering pulse
Semains oFF until the
voltage capacitor has to chae minimum
4 A minimum sanat width as the olp i.e, PlM
pulse
voltage e get minimum
Demodulation Pm Si_nal
yo PuM signal
schmit tig
Rarnp
neat

Synchoniation LPF
pulse genexdto)
 is pried t sçhmit tigge npise in the PuM
* PWM signal civcuit vemove S the
trigge
4 The schrit applied vop genoato
to the
wave form signa is
genevate& PUM geneator. duratond
The
4 synchrornization pulseprduces amp for the to width
4 amp geneHato proportional
The height o ramps are
4 that produces
thesuch
pulses PaM pulses synchionous pilse genenatoy pulse width.
hond amplitude 6
the othes
with
constant
& the olp ramp
ekorence pulses eference pulses Adde
+ These pulses help of then -Ve
added toith the to the level shit ter
geneato s giuen Finallythe op
adden is rectitiex modulating
olp clippedby to recoves the
4 The oavetorm is LPF
pat ¢ passed thvough a
rectifier is
sgnal
Adiontaqes: compaed to PAM.
& less when easy
PWM nose
noiseSepanation s Very between tiansm
sgnal to synchronisation
a. doesnot vequire
3 Pha cefvey
& de
-tter
Disadvantagese mnose Companed to PAM
thercfore theis
Bandudth
is in width &
pulses are Vanging
In PhM Vaiable
Content is
pouey
wavetams
H op
Shmit

elp
YOmp
st genenat
 Addes

leve
t shi<ta

Recovey
modulahing
Pulse Position Modulation -’
wid th ¬ amplitude of the pulses are kept
+ In PPM, the
Corstant
the position of each pulse with erence to the
changed acording to the inston
4 lathile
position 4 eerence pulse is the modalating aal
taneous amplitude vatue the instona
- pulse caricx is Naried with
4 The position
-eous value 4 messoge sgnal
Base band
sigral
peiodic 6cquertial
pulses
 PrM

PhiM, eoch tailing edge 4the

pPM is cbtaincd fom the pulse in the ppm.
PM is a sBating point
Geneyationg PPM
modulatig
sgnal PlWM
PWM shnal monastahle , PPM
mullivibratoy
to
Saototh,
signal olloied by the monosto
PhltM genesator
-ble multivibxator fied dunation from
PPM, op high tos
emains
+ Since
in
the PhlM signal thigger ip
the thailing edg PlN signal is uccd to
trailing cdge o the
+ The monostable multivibrator
torthe cicuit:
PPN qator morostable multivibiotth
Proctical diyferentiatos & a
4 Tt Consists is a PulM waveform
the cerentiatos
4 The ip comespondng to
+ Tthe diferentiatos e G-e Spikes waejorm
trailing edgs 4 the PlM
leoding &

R
D
3 -o PPM
C
olp
pWM
pulses 5

Diode D is used to bypass the tue spikes

+
ae sed to triqg1 the monostable
4 the -ve spikes
mutibator
 * The
onostable multivibator
Sarne todth 6 amplitu
de
postion rnodulated wove tor
orth eBeenr to tiggm the

puba
hhh t putse

PP Signals:
De modulation
fPMpulses Recoveed
PWM
pulss PWM modulairg
R Flip Jdematu
s Flop - ator

flop civcuit i set o)

* ttere p reteerce
tuxned 'ON' ohen the
Reteence putse aives
veference pulse is gnerated by
4 This qenenoter the eteivy
e}erence pulse shnal hrorn
Syrchoreatio wtth the synchronization
transmitte leading
tuvned ott at the
ckt is Yeset or repeots ue
* The tliptlop modulated pulse This
-the position tlop.
get PhliM pulses ot the olp t tp demodyat
dermoduated byPWM
Then PM pulses unred
orignal modulating sgna pOstion
-ated pulses
to get

higeig
patses
 elp

Aduantages PR constant, so eBect of noise is

is
| Arrplitde easy tunsmssion
tpanation s very amplitude
Si¡nal &nas pulse coth §
Due to Constant Some
. each pulse
is
peoen tox
Disadyantages RM -> Jequied
btw TX& Rr is
Synchronizatíon more Compased to PAM
1: is
Bard oidth
PAM, PM & PPM :
Corgpaison
PPM
PWM
PAM
avetorm t Wavetovm
1 Wavetorm

the Width pulse is a- position c the

3. Amplitude e proportonal to amrpit putse &propostional
pulse is proportonal -ude q modudating to the ampitude
to amplitude modu
|sral. the modulatirg siyral
-lating sanal
3. Noise is less 3 Noise is less
3 Noise is more

Conper 4 ystem i simp4 systen is Simpe

4 system is Smila to PM
Sirnila to AM 5 Sinilar to FM 5

6 poO tilization?
G poubey utlization
poue utilizatiorn Constant
less &
is more

.Bw is nore Comn

Bondubidth is le ss. Bad width is to PAM¬ ess compe
moYe
to PhM
Suontizaticn->
the Sample voues to the
Guantization approximates
trom a set ¢ tinite discoete level
neavest díscxete value
Quantizafon
Thexe aYe two types Quantized levels ar uniform
-
Unitom Quantiation Quontzation levels ane
Non- unom Quantizaticn - uneaqunl
Q too unitorm Quantizers
QYe

Mid-rise type
Q. Mid- tread type

Mid tread
Mid- íse.
Kmax - min
Guontizatíon step size 4
Quantizcd evels
Kmax - nio

yepresert eoch level

bits wsed to

Quanfzation
data ->
-transisspn
is the Sending intosmatton
transmission
Cemmunications media in the ton a
Data
 Transmissíon 4 sinals -that vazy discretely with tine
betoeentoo values Some Pyoical auantity, h
one valuc
nmbe the
sepresenting the binary
values tor the tonsmissicn
use discacte Communicatíon me dium
binary intormatton over a
tele coromunic tíon link.
OY a
network cabe
guch as

arollel transmissicn
Seriat &
Seial tonsroission: lows rom one
tansnissíon, data - bitunícation channe
+ In serial -time ia a comm Sexiol transmissin,
a
dota bt at tirne in
cenVeyed ata
bit Stop bit
oith a stayt Sinultanco
Posalle! transmission binary bits
rmultpk
neans transmiiting
4 Tt data transrission:
-usly in tronsnission
Seyial transnission Poxallel
transmis Sion s the
key tansoissio o ß Paralel-ransmisslon in which
|Senial tansnissinmede
type q mattple parallel inks arebit
| De~inititcn theohich a inge comuri|used that tonsmt each
in used to data simutanecusly.
-cortion tink fs fron
tronste the data
anoth
Cne end to tronstered at ore
bonsie 8-bits
Cnly one bit is clock pube
Bit
ransmisoo-ed at one cock
pule
used in Multipk inks need to he
|As siogle link is inemented fn cAe
Cost
sexfat hnsmission it con le! tronnissfon, hence
4fciency e relemente dtocatlyspenda 1s net cost eficient
koithort aving H is Cost
huge amount
 Cost eicient
ton
As stngle oit gets ae 8-bits gets transtened os
elock clock in Case d le| transrisa
per
íal thonsissin, its hence t is moxe eicient in
--nce

is componotvey exfomonae
pesfermonce
compaedto llel
ower as
ansmissíon
Short distonce
leterenlong dstonce transmission
tansmissión

less Complex Mose complex

Cnpbrty

Serden Receiver
transmi_sion
a) Seia

Paralle transmissior

Dota Conestoos-’ Corvesters

o datoa
too types orvetey
Aralog to ngtal Convestey
Digital CorverdeY
analog
oe want o Connect he olp of a cntut,
 ilp a digitat rCut, then ur hve to plae
circuit betwecn them an
inteafacirg
* Thís inter7acing cir cuit tthat converts the anatog
to Dtat
dgnal fnto digital signal is calle d as Ahalog
convexter.
Analog Converter:
Diitol to dp f a digi tal cir cuit,
Lwant to Connect the
then we have to plae
a analog cir cçt,
ilp beteen them'
cir cçt
an frtertacing that conveyts the digita
cicit Dgital o
s This interfacing is called as
into analog signal
Convestey
Aralcg

Anatog to Digital to
Dgital
processch|
Ahalog
Convessien |Convexson
alse cpde Modulation -

Aralog
messoge Tran Smittey section

charnel given to
olp Regerevabive Regereai channel
Repeater channe! Pepeates

circuit
ReconstauctonDestna-ion

Receivey Section
douw pass fltevo
ohich k grdes thon ti,
the Ip analog ignn to nveid alni
present in mssnge aignal,
theyueny the
highest
the messag sjn
colled the conmpe
to
ampler: the techniue whch he messag sihnal,
(ps e

+ his isinstontanecus values

data at onginal gnal toie the bghod
the thon
to veconstruct
Sampliog vate must be geater
ignal in ococance
sk The Comprert 4 rnessage
tequency theore tn
oith the sornping abm
ts bits and
ssive
Guantizey:- veducing the cxce
which gíveo to
a piocess Sampled olp
+ H is "he the
data bits G compaess
confining the the
tedundant
Quantie, Yeduces
value
the encody:
Encodes: sinal is done hy
digitizaton o analog levelby a binary
code
quontizcd ard-hold pbce S5
designates coch Sample
+ It Sompling cone hexe i& the Quonthizer l l oct as
t The sections PF, Sample
thyee
+ These to digital converte
the bonduidth used
iomizes
+ Encoding
Regenenative Repate,i strength
ineenses the signal
Tthis section one neqeneratve epeat
+ channel also has (
eConstuet te
"Tthe clp the loss
compensate the gnal
circut, to its strength.
Sígnal, $ alse to incveave
Decodey:
decodes cÉncuit decode, the putse coded woelon
+ the
 seCcduce the cgnat signal 7his Cicait acts asthe
demedulator

Reconstruction tey:analog conversíon ís dore by the

digital -to-
a loo pass filesgetisback
cuit &the decodey,
genesatie seconstuction iltey to
employed, called as the
the
onginasignat
Modulation -> the sampling bate is
modulafion, where se ater quantization
The type cohich the stepmodulatoo is textned as
much highes in
Smalle value4, Such a
¢ a
sdelta quantzer 6a
medulation: a t-bt
of
modulator comprises
gummerciscuits
lta
4 the de along oith two
circuit alnts): v(oTs)
deby sompled |-bit
Quontizey olp

Delay
uloTs)

2ínT) Over sampled ilp

ip
eplots)> ummer olp G quont
’ quantizer olp

circait
u(nT)’ p ¢ dlay
4 Dermod
olp
Deayk
Ts
 DM
PCM
tor Delta
DM stands
| PeM stand1 tor Palse Modulation
Code modulation n
back exists
3. feed
Feed back docsnot exist transmittey
8.
Yeceives wed pey
in tonsmittex ¬ enly one bit s
16 bits 3
4,8 os mple
sampk louoest bandoidth
banduotdth
tighut 6 snple fo tesms
impementotior
Compex în terms f
implementationlomplexity
complesity G cheap
6 Costy Signal to noise
noise Poo
qpod signal to xaio
tatio can modulate¬
Signal eguires encodu 8. signal
demodulate
8
both sides
E decodey
Used in spee ehes as well
q-
led in video te<epoy os images
&Qudio telephony