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1. Compare Bandwidth and power requirement in terms of carrier power PC , for AM, DSB-SC and SSB? Ans: Description AM with carrier DSB-SC AM SSB-SC-AM
Bandwidth
2fm
2fm
Fm
Power Saving 33.33% 66.66% 83.3% . !hat is meant "# frequenc# trans$ation? Ans: Moving a modulated radio-frequenc carrier !ignal to a new location in the frequenc !"ectrum without di!tur#ing the relation!hi" of the carrier to it! !ide#and!. %. !hat are the ad&anta'es of (esti'ia$ Side Band? Ans: $ &ffer! a com"romi!e #etween SSB and 'SB-S( $ )SB i! !tandard for tran!mi!!ion of *) and !imilar !imilar !ignal! $ Bandwidth !aving !aving can #e !ignificant if modulating !ignal! are of large #andwidth a! in *) and wide #and data !ignal!. ). Define the modu$ation inde* of +M. Ans: +t i! defined a! the ratio of ma,imum frequenc deviation to the modulating frequenc. =
f/fm
. ow is the narrow "and +M con&erted into wide "and +M? Ans: *he narrow#and FM !ignal can #e converted to a wide#and FM !ignal # !im"l "a!!ing it through a nonlinear device with "ower P "ower P . Both the carrier frequenc and the frequenc deviation ∆ f of the narrow#and !ignal are increa!ed # a factor P factor P . . A carrier is frequenc# modu$ated "# a sinusoida$ modu$atin' frequenc# /0, resu$tin' in frequenc# de&iation of 0. !hat is the "andwidth occupied "# the modu$ated wa&eform? Ans: iven/ f m 0 2 14 5f 0 1. *o find/ Bandwidth of the modulated !ignal B7 0 2 5f 9 fm fm 0 2 : ;<3 9 2 : ;<3 B7 0 ;=1. 2. 3$$ustrate the re$ationship "etween +M and PM, with "$oc dia'rams. Ans:
Modulating 7a 7ave
Diferentiat
Frequency Modulator
PM 7ave
(arrier wave Modulating 7a 7ave
Integrator
Phase Modulator
(arrier wave
FM 7ave
4. !hat is meant "# detection? 5ame the methods of detectin' +M si'na$s. Ans: 'etection or 'emodulation i! the "roce!! # which modulating voltage i! recovered from the modulated !ignal. +t i! the rever!e "roce!! of modulation. Method!/ Slo"e detector and "ha!e di!criminator. 6. !hat are the ad&anta'es of 7atio detector? Ans: >a! to align. )er good linearit4 due to linear "ha!e relation!hi" #etween "rimar and !econdar. ?m"litude limiting i! "rovided inherentl. So additional limiter i! n ot required. @educed fluctuation! in out"ut voltage. 18. Distin'uish "etween narrow "and +M and wide "and +M. Ans: S$.5o
Parameter9 Characteristics
!ide"and +M
;.
Modulation +nde,
reater than ;
2. 3. =.
Ma,imum deviation @ange of modulating frequenc Bandwidth
C 3< to ; C 25f 9 fm
5arrow"and +M Ae!! than or !lightl greater than ; C 3< to 3 Ch 2fm
11. Define white noise. State its power spectra$ densit# Ans: Man t"e! of noi!e !ource! are au!!ian and have flat !"ectral den!it over a wide frequenc range. Such !"ectrum ha! all frequenc com"onent! in equal "ortion4 and i! therefore called white noi!e. *he "ower !"ectral den!it of white n oi!e i! inde"endent of the o"erating frequenc, which i! given a! Sw ;< = 58 9
1. Define a random &aria"$e. Specif# the samp$e space and the random &aria"$e for a coin tossin' e*periment. Ans: @andom varia#le i! defined a! a rule or ma""ing from the original !am"le !"ace to a numerical !am"le !"ace !u#Dected to certain con!traint!. @andom varia#le i! al!o defined
a! a function where domain i! the !et of outcome! and who!e range i! @4 i! the real line. ?ll our random varia#le! will #e defined on finite !am"le !"ace!. *he "o!!i#le outcome! for one coin to!! can #e de!cri#ed # the samp$e space = >heads, tai$s. 1%. !hen is a random process ca$$ed deterministic? Ans: ? random "roce!! re"re!ent! an en!em#le of time function!4 the value of which at an given time can #e "re-determined or !"ecified thu! a determini!tic "roce!!. @*: Et 0 ? co!t 9 G where ? and are con!tant and G i! a random varia#le. &nce the "arameter G i! determined4 Et a! a function of time i! entirel !"ecified and i! thu! a determini!tic "roce!!.
1). !hat is coherent s#stem? Ans: *he frequencie! u!ed for demodulation are !nchronied to o!cillator frequencie! generated in the tran!mitter i! !aid to #e coherent !!tem. 1. Compare the noise performance of DSBSC recei&er usin' coherent detection with AM recei&er usin' en&e$ope detection. Ans: S$.5o
Parameters
;.
SH@& and SH@(
2.
Bandwidth
3.
*hre!hold effect
=4
Hoi!e "erformance
AM @n&e$ope< SH@& 0 ma2 I 29 ma2 $ SH@( 2fm ?M e,hi#it! a thre!hold effect for low Si I Hi
Poor
DSBSC Coherent<
SH@&0SH@( 2fm Ho thre!hold effect Better noi!e "erformance than ?M
1. Define entrop# and its properties. Ans: >ntro" i! the mea!ure of the average information content "er !econd. +t i! given # the e,"re!!ion E0P,ilog2P,i #it!I!am"le. Pro"ertie!/ ;.
C= max{P(X!" I(X#$!