COMMUNICATION ENGINEERING 2 MARKS

EC6651

COMMUNICATION ENGINEERING

3 0 0 3

1. ANALOG COMMUNICATION

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AM – Frequency spectrum – vector representation –  power relations relat ions – generation of AM – DSB, DSB/SC, SSB, VSB AM Transmitter  !eceiver" FM an# $M – frequency spectrum –  power relations % &BFM  'BFM, (eneration of FM an# DM, Amstrong met)o#  !eactance mo#ulations % FM  $M frequency* +* DIGITAL COMMUNICATION

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$ulse mo#ulations – concepts of sampling an# sampling t)eormes, $AM, $'M, $$M, $TM, quantiation an# co#ing % DCM, DM, slope overloa# error* ADM, D$CM, --.  systems – AS., FS., $S., BS., $S., AM, MS., (MS., applications of Data communication* (Qualitati ! "#l$% 0* SOURCE CODES, LINE CODES & ERROR CONTROL (Qualitati!

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$rimary communication – entropy, properties, BSC, B1C, source co#ing % S)aum, Fao, 2uffman co#ing % noiseless co#ing )eorem, B' – S&! tra#e off co#es% &!3, !3, AM4, 2DB$, AB, MBnB co#es % 1fficiency of transmissions, error control co#es an# applications% convolutions convolutions  5loc6 co#es* 7* MULTILE ACCESS TEC'NIQUES

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SSMA tec)niques % FDMA, TDMA, CDMA, SDMA application in wire an# wireless communication communication % A#vantages 8merits9 8 merits9 % :* SATELLITE, OTICAL I)ER – O*ERLINE, SCADA

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-r5its % types t ypes of satellites % frequency use# us e# lin6 esta5lis)ment, MA tec)niques use# in satellite communication, eart) station" aperture actuators use# in satellite – 4ntelsat an# 4nsat% fi5ers – types% sources, #etectors use#, #igital filters, optical lin6% power line carrier  communications% communications% SCADA TOTAL - 5 ERIODS TE+T )OOS ;.T aub & Schiling “Principles of communication communication systems” T ata McGraw hill

2! 2." .#as “Principles of $igital communication” communication” %ew  ge 'nternational( )*+,

/ MARS QUESTIONS AND ANS*ERS UNIT I ANALOG COMMUNICATION COMMUNICATION 1. D!i#! a2litu! a2litu! M"ulati"#. M"ulati"#.

Amplitu#e Mo#ulation is t)e process of c)anging t)e amplitu#e of a relatively )ig) frequency carrier signal in proportion proportion wit) t)e instantaneous value of t)e

mo#ulating

signal* +* D!i#! M"ulati"# i#!4 a# 2!!#t "ulati"# " a# AM 7a!. Mo#ulation in#e< is a term use# to #escri5e t)e amount of amplitu#e c)ange present in an AM waveform *4t is also calle# as coefficient of mo#ulation* Mat)ematically mo#ulation in#e< is m = 1m/ 1c ')ere m = Mo#ulation coefficient 1m = $ea6 c)ange in t)e amplitu#e of t)e output waveform voltage* 1c = $ea6 amplitu#e of t)e unmo#ulate# unmo#ulate# carrier voltage* $ercent mo#ulation gives t)e percentage c)ange in t)e amplitu#e of t)e output wave w)en t)e carrier is acte# ac te# on 5y a mo#ulating signal* 0* D!i#! L"7 l!!l M"ulati"#. 4n low level mo#ulation, mo#ulation ta6es place prior to t)e output element of t)e final stage of t)e transmitter* For low level AM mo#ulator class A amplifier is use#* 7* D!i#! 'i8 l!!l M"ulati"#. 4n )ig) level mo#ulators, t)e mo#ulation ta6es place in t)e final element of t)e final stage w)ere t)e carrier signal is at its ma* Di:ti#8ui: * Di:ti#8ui: i#8.

4n )ig) si#e in@ection trac6ing , t)e local oscillator s)oul# trac6 a5ove t)e incoming !F carrier 5y a fii#8* 4n low si#e in@ection trac6ing ,t)e local oscillator s)oul# trac6 5elow t)e !F carrier   5y a fii#8 !".'"7 it i: !u!.

T)e #ifference 5etween t)e actual local oscillator frequency an# t)e #esire# frequency is calle# trac6ing error*4t is re#uce# 5y a tec)nique calle# t)ree point trac6ing* ;+* D!i#! ia8! !=u!#$ !?!ti"# ati". T)e image frequency re@ection ratio is t)e measure of t)e a5ility of preselector to re@ect t)e image frequency* Mat)ematically ,4F!! is 4F!! =8;+r+9;/+ ')ere r= 8fim/f!F98f!F/fim9 ;0* D!i#! '!t!"$#i#8. 2etero#yne means to mi< two frequencies toget)er in a nonlinear #evice or to translate one frequency to anot)er using nonlinear mi* D!i#! a:!#i#8 #"!. T)e point w)ere a polar or incline# or5it crosses t)e equatorial plane traveling from nort) to sout) is calle# ascen#ing no#e* ;?* D!i#! li#! " #"!:. T)e line @oining t)e ascen#ing an# #escen#ing no#es t)roug) t)e center of eart) is calle# line of no#es* ;* D!i#! a#8l! " !l!ati"#. Angle of elevation is t)e vertical angle forme# 5etween t)e #irection of travel of an electromagnetic wave ra#iate# from an eart) station antenna pointing #irectly towar# a satellite an# t)e )oriontal plane* ;E* D!i#! Aiut a#8l!. Aimut) is t)e )oriontal angular #istance from a reference #irection, eit)er t)e sout)ern or nort)ern most point of t)e )orion*

;;* *at a! t! aa#ta8!: " "2tial i !t!t". T)e function of an AM #etector is to #emo#ulate t)e AM signal an# recover or  repro#uce t)e original source information*T)e recovere# signal s)oul# contain t)e same frequencies as t)e original information signal an# )ave t)e same relative amplitu#e c)aracteristics*

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