Communication System Engineering

Transcription

1 Couiio Syse Egieerig PE5I NLOG COMMUNICION (--) (5 h Se ECE- EC) MODULE-I. SIGNLS ND SPECR: Overview o Eleroi Couiio Syses, Sigl d is Properies, Fourier series Epsio d is Use, he Fourier rsor, Orhogol Represeio o Sigl.. RNDOM VRIBLES ND PROCESSES: Probbiliy, Rdo vribles, Useul Probbiliy Desiy uios, Useul Properies d Ceri ppliio Issues.. MPLIUDE MODULION SYSEMS: Need or Frequey rslio, pliude Modulio (Double Side Bd wih Crrier DSB-C), Sigle Sidebd Modulio (SSB) Oher M ehiques d Frequey Divisio Mulipleig. MODULE-II. NGLE MODULION: gle Modulio, oe Moduled FM Sigl, rbirry Moduled FM sigl, FM Modulors d Deodulors, pproiely Copible SSB Syses. 5. PULSE MODULION ND DIGIL RNSMISSION OF NLOG SIGNL:log o Digil (Noisy Chel d Role o Repeer), Pulse pliude Modulio d Coep o ie divisio ulipleig, Digil Represeio o log Sigl MODULE-III 6. MHEMICL REPRESENION OF NOISE: Soe Soures o Noise, Frequey-doi Represeio o Noise, Superposiio o Noises, Lier Filerig o Noise. 7. NOISE IN MPLIUDE MODULION SYSEM: Frework or pliude Deodulio, Sigle Sidebd Suppressed Crrier (SSB-SC), Double Sidebd Suppressed Crrier (DSB-SC), Double Sidebd wih Crrier (DSB-C). MODULE-IV 8. NOISE IN FREQUENCY MODULION SYSEM: FM Reeivig Syse, Clulio o Sigl o Noise Rio, Copriso o FM d M, Pre ephsis d De-ephsis d SNR Iprovee, Noise i Phse Modulio d Mulipleig Issues, he FM Deodulor usig Feedbk (FMFB). ddiiol Module (eril Eiio-Ierl). MPLIUDE MODULION SYSEMS:Rdio rsier d Reeiver.. PULSE MODULION: Pulse Widh Modulio d Pulse Posiio Modulio.. SYSEM NOISE IN FREQUENCY MODULION:hreshold i Frequey Modulio, Clulio o hreshold i FM Disriior. PEL6I COMMUNICION ENGINEERING (6 h Se EEE) MODULE-I INRODUCION: Elees o Eleril Couiio Syse, Couiio Chels d heir Chrerisis, Mheil Models or Couiio Chels FREQUENCY DOMIN NLYSIS OF SIGNLS ND SYSEMS: Fourier series, Fourier rsors, Power d Eergy, Splig d Bd liied sigls, Bd pss

2 sigls MODULE-II NLOG SIGNL RNSMISSION ND RECEPION: Iroduio o odulio, pliude Modulio (M), gle Modulio, Rdio d elevisio brodsig MODULE-III PULSE MODULION SYSEMS: Pulse pliude odulio, Pulse ie Modulio PULSE CODE MODULION: PCM syse, Iersybol iereree, Eye pers, Equlizio, Copdig, ie Divisio Mulipleig o PCM sigls, Lie odes, Bdwidh o PCM syse, Noise i PCM syses, MODULE-IV Del Modulio (DM), Liiios o DM, dpive Del Modulio, Noise i Del Modulio, Copriso bewee PCM d DM, Del or Diereil PCM (DPCM), S-ry Syse

3 MODULE-I Elees o Eleril Couiio Syse Iorio Soure Speeh, Musi, Ige, Video, Isrueio d esuree sigls, EEG, ECG, Seisi, eeorologil sigls, D e (rsduers required) rsier Chel Reeiver Iorio Sik log (Poi-o-poi, brods), Low Power, Mediu Power, High Power, Digil ddiive, Lier ie Ivri, Lier ie vryig, Bd liied, Power liied log Digil rsduers (Speker, Piure ube e) Iorio is obied ro rel lie sigls hrough he use o rsduers. For eple, speeh is overed io orrespodig eleril sigl by irophoe d ovig piure sigls re overed io he pproprie eleril sigls by vrious ers. he iorio so obied is lled sigl h beoes uio o ie whih is usully log i ure. Sigls y be desribed i ie doi or i requey doi. he requey doi desripio o sigl is kow s speru h would be overed subsequely. D geered by he keysroke o opuer beoe he iorio whe ouiio is de hrough e-il. he rsier y opere i poi-o-poi ode or i brods ode wherei here is uber o reeivers orrespodig o sigle rsier. I y be wired, wireless. he rsier y lso opere diere power levels depedig upo he ppliio, rge o servie d ype o servie. We ge hree disi ypes o rsiers: siple, hl duple d ull duple. he brods rsiers usully e or eerie purpose re siple ype s iorio low is uidireiol. he reeiver o ouie bk o he rsier. I hl duple syse, iorio low bewee he rsier d he reeiver i oe direio oly ie, bu o siuleously. he wlkie-lkie is eple o siple ype o ouiio. he elephoe provides eple o ull duple ype o ouiio. he hel y be odelled s ddiive oise ype: he hel irodues oise h is dded o he rsied sigl (sellie hels)

4 Chel + r Lier ie ivri (LI) ype: he hel behves s lier iler whose ipulse respose (or lerively he rser uio) does o vry wih respe o ie. he rsied sigl is ovolved wih he ipulse respose o produe he hel oupu. (Lesed ld lie elephoe lies or siply he elephoe hel) Lier Filer h + r h Chel Lier ie vryig (LV) ype: he hel gi, here behves s lier iler. However, ulike he LI hel, he ipulse respose o he hel vries wih respe o ie. he hel oupu is observed o be ovoluio o he rsied sigl d he ie vryig ipulse respose. Cellulr hels provide brigh eple o his kid o hel. Lier ie vryig Filer + r h; Chel

5 he reeiver s uio is o rerieve he origil rsied sigl ro oisy, disored sigls h rrive is ipu. log reeiver is erused wih he sk o repliig he origil wveor ro is oise orrup d hel idued disored versios. digil reeiver kes deisio (wihi splig iervl) s o whih oe ou o M uber o sybols. Perore eri o reeivers: Sigl o oise rio (SNR) reeiver oupu or he log oe Probbiliy o bi error or Me squre error (MSE) or he digil ype. he sik is usully speker h reprodues speeh sigls ro he orrespodig eleril oupu or piure ube h reprodues he piure. I y be opuer lso h is ieded o reeive e-il. Elerogei Speru ble No.. lloio o requeies or eisig ppliios S Frequey Noelure ppliio/usge No Rge Hz- Hz Ereely low requeies Uderwer Couiio (ELF) Hz-. KHz Voie Frequey (VF) elephoe. KHz KHz Very low requeies (VLF) Nvigio KHz- KHz Low Frequey (LF) Rdio vigio 5 KHz - MHz Mediu Frequeies (MF) M rdio brodsig 6 MHz- MHz High Frequeies (HF) M, eur rdio, obile 7 MHz Very High Frequeies V, FM, Mobile ouiios MHz (VHF) 8 MHz- GHz Ulr High Frequeies V, rdr, sellie ouiios (UHF) 9 GHz- GHz Super High Frequeies (SHF) erresril irowve d sellie ouiios 5 GHz 6 GHz Opil Frequeies Opil ouiio Sigl lysis: Fourier Series sigl is periodi i i repes isel er eri ie; where is is period. ep where ep d

6 wo sigls d d re sid o be orhogol over period i heir ier produ is zero; or he se whe he sigls re rel vlued uios. For eple: over he period V si d os, si, si re orhogol o eh oher V V V he udel requey is epressed s he sigl us sisy se o odiios kow s Dirihle s odiios hese e ) he sigl is bsoluely suble over is period d he oeiie os d d b si d b b d where Fourier rsor o uio is evlued s ep d Q. Show h d u Proo: u u d d his is beuse u or. Q.. Fid he speru or sigl deied s v si os

7 Sol: he sigl is si os si si v he speru orrespodig o he irs er is he speru orrespodig o he irs er is Q.. Fid he speru o sigl deied s Sol: We kow h d d dg d he uio g G, he g G d d G g Le us diereie he uio g g obi d d g d d d siilrly, g g G oe ore wih respe o ie. Hee, we d d Fro he lieriy propery o he Fourier rsor operor, we hve, orrespodig o he seod er o he epressio, g G (Muliplyig o boh sides ) dg hus, he Fourier rsor o he uio is obied by wriig d dg d G G G G Q. Fid he Fourier rsor o uio give s Fro he requey diereiio propery o he Fourier rsor, we hve

8 d d.. d d d. d Q. Fid he Fourier rsor o sigl give s y d d Sol: Diereiig uio like d d d d d d d d Fro he bove, we oe h, d d d d d d i he ie doi, we hve d d. However, ro he lieriy priiple, he ie diereied uio hs wo prs; he rsor orrespodig o. hereore, Y d d y d he oher orrespodig o Y d d d d d d Q.5 Fid he Fourier rsor o sigl deied s y Sol: y

9 We kow h, or ep * * his is beuse d d d d d Le d ep ep ep ep Q.6 Fid he Fourier rsor o sigl give s y Sol: s i he previous proble, d d d d d d Y d d ep ep ep ep * * * * * Fro he lieriy propery o he Fourier rsor, we hve d d d d y ep ep ep * * * * *

10 he ipulse hs o heil or physil eig uless i ppers uder he operio o iegrio. wo o he os sigii iegrio properies re I. Repliio propery o prove his, we wrie d d d d le d We kow h, is vlue o. hereore,. d his is kow s repliio propery. II. Splig propery We lso hve, d o prove his, we oe h d d Hee he bove iegrl beoes d

11 We kow h, is vlue o. hereore, he bove iegrl hs us oe vlue h is ozero ourrig d his vlue is give s his oplees he proo. III. Furher, we hve his is beuse he ipulse uio hs vlue o. Hee, oly oe vlue o he uio is reied whih ours. his is beuse Le us evlue d Le d d hereore, d d IV. o prove his, we wrie Le d

12 d d Subsiuio o he bove i he iegrl gives us d d his is beuse he ipulse uio hs vlue o. Fro he previous proble we ge his. V. d Le d d hus, d d d lile eesio o he his resul s pplied o ipulse uios give us VI. Sol: Le us prove his usig he Fourier rsor properies. We kow h,

13 ep ep hereore, ep ep ep Prove he duliy heore o Fourier rsor whih ses h i Proo: ep Hee, d ep d Le us ierhge he roles o requey d ie i he bove epressio hereore, ep d Fid ou he Fourier rsor o. Sol: We kow h, ep Le hereore, d ep d, he

14 ble. Soe ooly used uios d heir Fourier rsors re W si ep u, ep, si re W 5 ep ep 6,, ep u 7 8 sg() 9 u si W ep Prove he 7 h ery o ble. ro he pproprie propery o he Fourier rsor. Sol: he pproprie propery h we use o prove his is he requey doi diereiio whih is d d s we oe h,

15 ep, ep d d d d u u his oplees he proo. Prove he 9 h ery o ble. usig pproprie properies o Fourier rsor Sol: We ke use o he previous resul. he uio uder osiderio y be epressed s he posiive goig pr y lso be osidered s liiig se o u ep li Siilrly, he egive goig pr y lso be osidered s he liiig se o he previous uio however, wih reversed ie u u ep ep li Le us obie he Fourier rsors o he wo uios For he liiig se o, we hve li Prove he h ery o ble.. Sol: he Fourier oeiie o his uio is deied s ep d Hee, he Fourier series o ipulse ri is epressed s

16 ep he rigooeri Fourier series would osis o he oeiies s d b os d si d b Fro he h ery o his ble, we oe h ep hereore, he Fourier series orrespodig o ipulse ri is epressed s he Fourier series o soe ooly used wveors. Hl wve reiied sie wve o pliude vol os si os8 6 os 6 5 os 5 os si. Full wve reiied sie wve o pek pliude vol os os8 6 os 6 5 os 5 os. Regulr or squre wve o pek o pek pliude vol si si 7 7 si 5 5 si si k. rigulr wve... si 7 9 si 5 5 si 9 si 8

17 Fig.5 he wveor is epressed s his uio ehibis odd syery. Hee i ois he sie ers oly. he oeiie b is evlued s d d d d d b si si si si Le us evlue he bove oeiie er by er. he irs er gives us os si 8 os si 8 os si. he seod iegrl beoes os si os si 8 os si os si 8 os si. si d

18 he hird iegrl beoes os os os os os si d he ourh iegrl is os si os si 8 os si os si 8 os si. si. d he ih iegrl beoes os os si. d o Cobiig ll he ers, we obi os os os si os si 8 os os os si os si 8 os si 8

19 For vlues o beig eve, he ers si vishes d os beoes he er os lwys. Siilrly, or odd vlues o, he er os his is sipliied o si os. 8 si os. si si si si si 8 os os si si si si os si os 8 os os si si 8 si 8 i We oe h, i, he bove er is 8, or, i is 8, or 5, he bove er is 8. Hee he series pliudes beoe lerely posiive d egive d vry he re o. hus, he Fourier series epsio o he rigulr wveor s show i Fig.5 is... si 7 9 si 5 5 si 9 si 8

20 8 si si si 5 si For he bove rigulr pulse, he Fourier series is obied by oig h i be obied ro Fig. 5 by shiig i by hl period. si si 8 9 si 5 si os os os 5 os Full wve reiied rigulr wve si si si 5 si his wveor ehibis eve syery. his hs verge vlue give s d.. he wveor is epressed s he orrespodig iegrls beoe

21 os os si os si os si. he seod iegrl beoes os si os os si os os si os si os si os si os si. si d he hird iegrl beoes os os os os os si d

22 si os os os os si os os os si os os Hee, he Fourier series beoes si 8. rpezoidl wveor he wveor is epressed s he irs iegrl is os si 6 os 6 6 si os si si 6. 6 ^ d he seod iegrl is

23 os os 6 os os os si. 6 6 d he hird iegrl is os os os si os si si 6 d We oe h, he er. os..si os os he ourh iegrl is os 5 os si. 6 5 d he ih iegrl is 5 os os 6 5 os 5 5 si os si si d Cobiig ll he ers, we hve

24 6 5,7,...,., 6 os si. os. si.. si si. si si si si si si si 5 si si si si..si. si os os 5 os os 5 6 os 5 os os os os 5 os os 6 5 os 5 5 si os si os 5 os os si os si os os os si re o vlues llowed he eiher o uliple be o i be eve o Here ers ll Cobiig I we obie ll he osie ers, he resul is zero. he desired Fourier series is 7 si 9 si5 5 si 6 9. periodi ipulse sequee (Ipulse ri) where is is period. he oeiie is evlued s

25 d Siilrly, d os s he del uio ri is eve uio o ie, he oeiie b is zero. he Fourier series orrespodig o suh ipulse ri is epressed s ep ep his is beuse he oeiie or he del ri he geerlized Fourier series o y rbirry periodi sigl is epressed s ep ep ep ep Here, we deie us oe period o he wve give s oherwise y rbirry periodi sigl y be epressed s kig he Fourier rsor o boh he sides, we hve

26 Coprig he wo resuls, we hve Hee, he geerlized Fourier series o y rbirry periodi sigl is epressed s, usig his resul ep ep kig he Fourier rsor o boh he sides, we hve For he spled sigl se, whe, we hve kig he Fourier rsor o boh he sides, ep We oe h, ep Hee, he Fourier rsor o ep is

27 Q. Fid he speru o ull wve reiied sie wve ro udels. spled sigl is epressed s s s s s s s s s s s s s s s s s s s ep I we opre boh he sides o he rsor, we oe h, s s s Fid ou he Fourier rsor o Gussi pulse give s ep Sol: he Fourier rsor is epressed s d d d ep ep ep ep By ddig d subrig er like o he rgue o he epoeil uio

28 ep ep ep u Le d du Subsiuig his i he bove, we ge ep ep u ep ep d du Ieree: he speru o Gussi pulse is lso oher Gussi pulse Seod Mehod: his lso be derived by oher ehod. Frequey doi diereiio o give sigl gives us d d d Suppose, we hve sigl h is desribed by irs order diereil equio epressed s d d kig he rsor o boh he sides, we hve I d d ep is oiuous sigl bdliied o rdis per seod, he show h k si k or k Proo:

29 k si k k k k beoes i he requey doi,. k k kig he iverse rsor we oe h, i he rge o equl o or requey rge o k. k k, he sigl would be ely We oe h, i order o replie he uio, he odiio is h k oherwise or k, ulipliio o he wo uios i he requey doi would resul i speru uilio o Hee show h, k si si si Proo: or Use o he bove resul gives us. or kig he iverse rsor o he bove resul we ge S No.. si or Noelure Mheil Desripio Lieriy b b ie Slig Duliy I he ie Shiig ep 5 Frequey Shiig (Modulio heore) 6 re uder ep d

30 7 re uder d 8 ie doi diereiio 9 ie doi d d iegrio d Frequey doi diereiio Cople ougio Re I Mulipliio i ie doi 5 ie doi d d d ovoluio d 6 Prsevl s * * heore y d Y 7 Ryleigh s heore d 8 Moes Propery d d d d d Prove propery 6 i ble. Proo: * * y d Y d * y d ep dy d y ep d d y ep dy * d * d

31 Ne we show he ovoluio o wo regulr pulses o diere pliudes d diere durios. he resul is observed o be rpezoidl pulse hvig durio equl o he su o he durios o he idividul pulses.

32 dλ - + dλ +

33 Obeive: Fourier rsor o Periodi Sigls We hve periodi sigl hvig period h sisies he Dirihle s odiios. s we hve see previously, his sigl is epressed s lier weighed obiios o is Fourier series oeiies s ep kig he Fourier rsor o boh he sides we ge ep ep We observe he ollowig ro he bove: h Fourier rsor o periodi sigl osiss o sequee o ipulses i requey uliples o he udel requey o he periodi sigl. he weighs o he ipulses re us he Fourier series oeiies o he periodi sigl hus we obi disree or lie speru orrespodig o periodi sigl Properies o Fourier rsor would be uilized o opue he Fourier series oeiies s ollows We deie rued sigl s oherwise his oly es h we re us osiderig oe period o he sigl d we hve se oher periods o zero. he periodi sigl is resored by repeig his rued sigl wih period o. Hee, we ge bk our sigl s Now, pply Fourier rsor o boh he sides.

34 Le us opre boh he rsors. We iediely see h he ollowig seps re ollowed o id ou he Fourier series oeiies : rue he sigl o us oe period. Deerie he Fourier rsor o his rued sigl. Evlue he Fourier rsor o he rued sigl requey o obi he h hroi d uliply i by Eple: Fid ou he Fourier series oeiies o rigulr pulse ri by his ehod. Sol: Fro ble., we oe h he rued rigulr pulse hs Fourier rsor give s si,, Hee, requey o, his beoes si Muliplyig i by, we obi si si. si si si

35 We observe ro he bove h, or rigulr wve, he Fourier series oeiies dey he re o d hey re lwys posiive. his is ser dey s opred o siilr durio regulr wveor. Obeive: o ler power, eergy d uoorrelio uio o give sigl. he eergy d power o sigl re represeive o he eergy or power delivered by he sigl whe he sigl is ierpreed s volge or urre soure eedig Ω resisor. he eergy oe o sigl, deoed by is deied s P li d d he power siilrly, be epressed s d sigl is eergy-ype i d is power-ype i P. sigl o be, hereore boh eergy or power ype sigl. For eergy ype sigls, P d or power ype sigls power-ype d hve power P d. Usully ll periodi sigls (wih he eepio o ) re I he bove, is he period o he sigl d is y rbirry uber. Eple: Fid ou he verge power i periodi sie wve. Sol: Le he sie wve be represeed s V si Where hus, P V V d V si V si d his is beuse os d V os d Eergy-ype Sigls he eergy o sigl y be epressed s d d V osos d.

36 d or d his ollows ro he h he eergy o give sigl o be diere wheher i is opued i he ie doi or i he requey doi. he equliy o he wo bove epressios is kow s Ryleigh s heore. Eple: Fid ou he eergy oied i sigl give s si Sol: I is esier o evlue he eergy i he requey doi. he speru o his sigl is si his is regulr pulse i he requey doi wih ui pliude d bdwidh o uis. hereore, d 5 d 5 uis Relio bewee ovoluio d uoorrelio o give uio We y opue he uoorrelio o eergy-ype sigl s R * d his is uio o he lg d lso gives us he relioship bewee he uoorrelio d ovoluio o give sigl. s he sigl is orreled wih isel or diere vlues o his lg preer, i is kow s uoorrelio. We re ryig o id ou he degree o siilriy bewee he origil wveor d delyed or dved versio o i. By seig i he bove, we obi R * d d d d Le us id ou he ie-verge uoorrelio uio d power sperl desiy o he power ype sigls. Le us ssue h is periodi sigl wih period h hs he Fourier series oeiies deied s R * li li k k k k d. he ie-verge uoorrelio uio or suh sigl is * * * d li d k k k d

37 hese seps were ollowed o eliie he liiig er d o epress he uoorrelio uio i ers o oe period o he sigl. he subsiuio o he Fourier series epsio i he bove yields d d d d R * * * * * ep ep ep ep ep ep ep ep ep ep We oe h, he uoorrelio uio o periodi sigl osiss o disree vlued power opoes loed iegrl uliples o he udel. he power opoes re proporiol o. kig he Fourier rsor o boh he sides, we obi R S ep ep ep his S gives us he power sperl desiy o he periodi sigl. Power sperl desiy es he disribuio o power o he sigl s uio o requey. he ol power oe o he periodi sigl is obied by iegrig S wih respe o requey. Whe his is doe, he power beoes P his relio is kow s Ryleigh s relio.

38 MODULE-II MPLIUDE MODULION Modulio o bsebd sigl y be viewed s low pss o bd pss oversio. his is usully oplished by ulipliio o he bsebd sigl wih periodi siusoidl wveor o requey higher kow s he rrier h h o he bsebd sigl. he bsebd sigl heeorh will be lled he odulig sigl. Mulipliio o he odulig sigl wih siusoidl rrier i he ie doi resuls i shiig o he speru o he odulig sigl i he requey doi. Le he odulig sigl be deoed s d he siusoidl rrier be si. Mulipliio o he wo i he ie doi geeres sigl v M epressed s v M si I he speru o be M, he he produ sigl V M M M v M hs speru give s where is he ople uber equl o. he bove epressio is beuse o he h he speru o pure siusoid eered wih pliude wih rrier o he or si o requey osiss o wo ipulses. I siilr shio, we oe h ulipliio o os gives us v M os he speru o his sigl kes he or o V M M M We observe h, he proess o ulipliio o wih eiher si or os hs give rise o wo ew requey opoes i he speru o he oupu sigl. hese wo requeies d re lled he upper side bd (USB) d he lower side bd (LSB) respeively. he proess o geerio o hese wo side bds log wih he rrier is kow s double side bd wih rrier (DSB plus C). he epressio or DSB wih ull rrier is v DSB C si si

39 s we y urher observe, i be geered by uliplier d dder irui. his is illusred i Fig. L9.. For eple: L, d 7 he ers ( ) L. he pulse k q is prese or he iss ro ( ) o. his lss or, hee sybol iervls. However, he shied pulse q k lss ro k o k L 7 h is whih hs sured o ½ s he pulse he 7 h sigllig iervl y origie his, y hve he 6 h pulse s is oly q k or he 5 h pulse y be he pulse wo iervls erlier. Hee, ll he vlues o would hve sured o ½ ro - o h sigllig iervl wheres he origil pulse, V si dder V si Fig. L 9. Coepul geerio o DSB wih ull rrier ype o M sigl For siusoidl odulig sigl, he iseous pliude o he rrier beoes V V si s he odulig sigl sis op he pliude o he rrier. s we re ieresed i he iseous pliude o he rrier s i should hge i orde wih he pliude o he odulig sigl, he overll oduled sigl looks like v DSB C V si V si. V V si V V sisi We deie he odulio ide or he deph o odulio o his ype o M sigl is deied s V V he rio o he pek pliudes o he rrier d he odulig sigl d i hs iu vlue o uiy. Usully, he vlue o, i order or evelope deeor o work he reeiver. I, we udersd i s % oduled sigl d or vlue o V si, we relize overoduled sigl. For sdrd M brods, he vlue o odulio ide is %. Depedig o he pliude level o he odulig sigl, odulor y be low level odulor or high level odulor. low level odulor y be osrued by ieig he odulig sigl eiher o he bse or he eier o rsisor. Le us sudy suh odulor.

40 is zero. V R R M Fro Crrier requey R C R e C e C Oupu Modulig sigl Fig.L 9. BJ pliier wih eier odulio irui o geere DSB plus C I Fig.L. 9., he d bis odiio is se up by he volge divider R d R, he eier resisor R e, olleor resisor R d he supply volge V. he volge gi o he BJ pliier depeds o is quiese eier urre. s he odulig sigl hs bee ieed io he eier, he iseous eier urre beoes i E I E K V os where I E is he quiese vlue o he eier urre d K is os. pliude odulio resuls i K V is sller h I E. s he volge pliiio is uio o he ol eier urre, we ge v K i E K I E K V os where K is oher os. he ipu o he pliier is he rrier volge oupled hrough rsorer, he oupu volge o his irui is V vv os K E I K V os os We observe h, pliude odulio hs bee hieved. he ued irui prese he olleor llows he wo side bds o pss hrough d suppresses oher hrois ro pperig he oupu. his osiues bd pss iler wih eer requey roud he rrier requey wih pss bd o.

41 low level odulio is lso hieved by ieig he odulig sigl o he bse o he rsisor. he irui or hievig his is illusred i Fig. L 9.. Fro rrier requey Osillor M Oupu Modulig Volge pliier V bb V Fig. L 9. BJ pliier wih bse odulio irui o geere DSB plus C oher irui o oplish DSB plus C geerio is he swihig odulor illusred i Fig.L 9.. V os v R L v Fig. L 9. Swihig Modulor I his irui, we ssue h he rrier pplied o he diode is lrger h he odulig sigl i pliude. I is urher ssued h he diode is idel swih whih iplies h or he orwrd bis odiio orrespodig o, i shows zero resise. he rser hrerisi o he diode-lod resisor y be odeled s piee wise lier. his es v v,,

42 where v V os. We observe ro he bove h, he oupu volge v vries periodilly bewee he volge v d zero wih requey o. he oupu volge, y lerively be epressed s v V os where g g is viewed s periodi pulse ri wih uiy pliude d duy yle o 5%, he ie period beig equl o us g. he Fourier series epsio o his pulse ri gives os Subsiuio o his i he bove epressio gives rise o wo opoes. he irs er is V os V is he desired DSB plus C opoe. he seod er h ois ll hrois re ilered ou by he use o bd pss iler wih eer requey o wih bdwidh o Squre Lw Modulor. squre lw odulor is show i Fig. L 9.5. his uses he olier propery o ive devie like diode, BJ e. he odulig sigl is relively wek. he oupu o he devie be reled o he ipu s V os Nolier Devie v v R L Fig.L 9.5 squre lw odulor h eploys olier devie v v v ued o where d re oss. he ipu volge is epressed s v V os

43 Hee, he oupu volge beoes v V os V os Epsio o he seod er i he bove gives us v V os V os V os V os V os os L. High Level Modulor LECURE- ll he rsiers eployig he previous iruis re kow s low level odulors. his is beuse he pliude o he odulig sigl is rher sll h y oe ro irop phoe or ypil video er like he vidio. pliiio o he oduled sigl kes ple er hese iruis. Hee suh iruis re kow s low level rsiers. For he high level odulio, he odulig sigl is pliied irs beore i pliude odules he rrier. his is usully rried ou i lss-c power pliiers. his is beuse, s he odulig sigl hs bee lredy pliied, i o drive lier power pliiers. Suh high level odulor eployig lss-c power pliier is show i Fig. L.. V Clss B pushpull power pliier M Oupu V os Fig.L. Clss B odulor d lss C power pliier he oupu o he olier devie (he NPN rsisor here bised o er u o by he rrier whih hs bee ieed is bse) beoes

44 v V os V os os (L.) osiderig oly upo he seod er i he power series epressio or he oupu o olier power pliier We observe ro he bove h, os V os V os V (L.) Is he desired DSB wih rrier. o relize deodulio wih siple, low os deodulors suh s evelope deeor, we hve o esure h he opoe wih os hs bee reeed by he ued irui (bd pss iler wih ere requey equl o he rrier requey) oeed o he olleor o he power pliier d hee does o pper he oupu o he odulor. L. POWER IN N M SIGNL oveiol (DSB wih ull rrier) M sigl epressed s v V os os (L.) M orrespodig o odulig sigl epressed s V oe odulio. os. his is oherwise kow s Fro (L.), i is observed h, V v M V os os os (L.) V he irs er i (L.) gives us power o. his is beuse periodi sie wve wih ui pliude suh s rrier hs ie-verged power equl o ½ W. Boh he seod d he hird ers give us equl powers o V s hese re lso 8 siusoidl wveors. he ol power, hee beoes i DSB plus rrier ype o M wveor, V V V V V V P 8 8 (L.5) We observe h ro (L.5), ou o his ol power, he rrier power is he odulig sigl gives us power o V. V P wheres

45 his rrier power represes wsge o power s i does o ovey y useul iorio. I he odulio ide hs vlue o, he he ol rsied power is.5 V. I we hoose o o rsi he rrier power, he we ully rsi power o.5 whih ous or power svig o 66%. his is so s he rrier does o oi y useul iorio bou he odulig sigl. I he odulig sigl is y rbirry sigl, he is verge power beoes ype o M wveor beoes wveor is P / P. P d he ol power i DSB plus rrier. Siilrly, he power i DSBSC ype o M. he SSBSC ype o M wveor will hve power oe o Obeive: LECURE- o ler DSB-SC odulio/deodulio ehiques () Bled Modulor Cirui I DSB-SC or o pliude odulio, rrier is suppressed s i does o ovey y iorio. his rrier suppressio is oplished i uber o wys. We sr wih bled odulor irui. his is relized by BJ/FEs or devies possessig olier hrerisis. Suh irui is show i Fig. L.. ½ e v gs i d Modulig Sigl ipu ½ e Crrier ipu v gs i d DSBSC oupu Fig. L. bled odulor irui relized wih wo FEs y irui h produes he produ o wo ipu wveors (he odulig sigl d he rrier) is bled odulor. he FE is used here s i hs rser hrerisi whih is olier, so h he oupu ois er equl o he produ o he ipu volges, besides oher ross ers. he rser hrerisi o he FE is los prboli d y be pproied s i d I v bv (.) gs gs

46 where I is he urre or zero ge-soure volge, d, bre oss. Sie he dri urres idd i d low i he opposie direios i he priry widig o he oupu rsorer, he eeive priry urre i p is i p i id v gs vgs bv gs vgs v v bv v v v d gs gs gs gs gs gs (.) his beoes equl o, upo ppliio o Kirho s lw o he ipu loops o Fig. L., v e e e e (.) gs d gs v We obi, p e b e e i (.) he RF oupu rsorer rees he low-requey er like e pssig oly he produ be e whih is he desired DSBSC sigl. However, geerio o DSBSC by his irui requires he wo FES hed opleely wih respe o I, d b. Oherwise, residul opoes would pper he oupu whih obviously is o he desired oduled wveor. hese dys he BMs re vilble i he iegred irui (IC) or. Moorol s N5 is oe suh IC. (b) Chopper pliier bsed odulor Fig. L. ()

47 R s R L E os E os Fig. L. Chopper bled odulor I Fig. L., hoppig o he sigl is oplished by he diode bridge re equl o he rrier requey. he sigl pplied o he bridge is he essge sigl plus he d bis. ll our diodes o he bridge odu durig he posiive hl yle o he rrier hereby givig o oupu volge d oe o he odu durig he egive hl yles o he rrier lerely whih kes he sigl beoig vilble ross he lod resise. he rrier is preveed he oupu by es o ued irui. os R os Fig. L. Deodulio o he DSBSC sigl produed by Fig. L. () For deodulio o he DSBSC sigl, we eed o uliply os by syhroously geered rrier os. he se iruis s hose used or odulio be used or deodulio. However, he deodulig irui diers ro he odulor i h he

48 oupu o he deodulor should oi low pss iler wheres he odulor hs bdpss iler is oupu. he low pss ilerig is provided by he RC obiio s show i he bove igure. he deodulio y be oplished by uliplyig he oduled sigl by y periodi sigl o requey requey, he i hs Fourier series give s I is ppre h, i he oduled sigl, he orrespodig speru beoes.i os M M M M is y periodi sigl o os is uliplied by his periodi sigl Fro he bove, i is observed h he resul speru ois er be ilered ou by low pss iler. oher or o he bled odulor is show i Fig. L. (b). M whih + os Fig. L. oher relizio o bled odulor Modulio is hieved by usig olier devies. seioduor diode is olier devie. olier devie suh s diode y be pproied by power series like i v bv rsisors d vuu ubes lso ehibi siilr relioships bewee he ipu d he oupu uder lrge sigl odiios. o lyze his irui, we osider he olier irui elee i series wih he resise R s oposie olier elee whose eril volge v d he urre i re reled s bove. he volges v d v re give s v os v os d he urres i d i re give s i v bv os b os os b i os Hee he oupu volge is give by v i R i R R b os d

49 he sigl i his equio be ilered pu by usig bdpss iler ued o he oupu erils. Seioduor diodes re oveiely used or he olier irui elees i his irui. ll o he odulors disussed bove geere suppressed-rrier pliude oduled sigl d re kow s bled odulors. ued o K os Squre wve requey Fig, L.5. Rig Modulor h uses ere pped rsorer ipu s well s he oupu he diodes i Fig.L.5 or rig s hey ll poi i he se wy. hey re orolled by squre wve o requey equl o rrier requey whih is pplied i logiudil er by es o wo ere-pped rsorers. Uder he ssupios o pere ere p d ideil diodes, here would be o lekge o odulio requey io he odulor oupu. Le us ssue he diodes o be idel. O he posiive hl yle o he squre wve servig s he rrier, he op d boo diodes beoe o d he sigl psses o o he oupu. Siilrly, durig he egive hl yles o he rrier, he digol diodes beoe o swihig o he op d boo diodes. Hee he essge sigl psses o o he oupu, however wih egive polriy. Le us id ou he kid o oduled wveor he seodry oupu o he oupu rsorer. he squre wve hs Fourier series give s os he rig odulor oupu is, hereore s os

50 here is o oupu ro he odulor he rrier requey, h is he odulor oupu osiss eirely o odulio produs. he rig odulor soeies is reerred o s he double-bled odulor beuse i is bled wih respe o he essge sigl s well s he rrier. Uder he ssupio o he essge sigl beig bdliied o, he speru o he odulor oupu osiss o sidebds roud eh o he odd hrois o he squre wve rrier s show i Fig. Here i hs bee ssued h so h sidebd overlppig is voided whih rises whe sidebds belogig o de hroi requeies d overlp wih eh oher. bdpss iler wih ere requey d bdwidh d ree ll oher opoes. he oupu would sele he sidebds eered roud LECURE- DEMODULION OF M SIGNLS () Deodulio o DSB wih ull rrier ype o oduled sigls Deodulio is he proess o reovery o he origil essge sigl ebedded i he M wve. his is oplished by he deodulor irui i he reeiver. he siples deodulor is reiier ollowed by low pss iler whih is lled diode deeor. V os C R V o Fig. L. Evelope deeor or oveiol M syses his irui is lled so s i respods o he evelope o he ioig M sigl. O he posiive hl yle, he diode odus d he pior C hrges o he pek vlue o he reiied volge. s he ioig sigl lls below his vlue he diode beoes o oduig. his is due o he h he ode side volge o he diode is less h he hode side volge. hus, he pior eds o hold he previously quired pek vlue. he pior dishrges hrough he resisor slow re. Durig he e posiive hl yle, he ipu sigl beoes greer h he pior volge d he diode srs oduig gi llowig he pior o hrge up o he iedie pek vlue. he pior dishrges slowly durig he o period o he diode whih resuls i sll hge i is oupu volge. Durig eh posiive hl yle, he pior hrges o he pek vlue o he ioig sigl d holds his volge uil he e posiive yle. he ie os RC o he oupu irui is dused i suh er h he epoeil dey o he pior volge durig he dishrge period will ollow he evelope pproiely. he oupu volge ow hs ripple opoe whih is ilered ou by oher low pss iler. he iseous M sigl is

51 v M V os y ie is,, he slope o he evelope is give by dv M d V si h priulr ie, he evelope is give s v M V os Le be he ie is whe he pior C srs dishrgig. y subseque ie, he deyed pior volge beoes v V ep RC, he re o hge o dey is dv d V RC V os RC I lippig o he egive peks o he odulig sigl is o be voided, he, he slope o he deyed pior volge us be equl o or less h h o he oduled rrier. his is equivle o syig h, V os V si RC si or, RC os his gives us upper lii or he irui ie os s RC. si os si Mkig iizio o RHS, he er os os whih iplies h si is iu whe Subsiuio o he vlues o he bove yields RC. he bove equio idies h, or % odulio, he produ RC should be zero whih is o pril. I prie, i is oud h or

52 RC he disorio i he diode deodulor oupu is o eessive. he highes requey h be deeed by his irui is High RC (b) Deodulio o suppressed rrier ype o oduled sigls os Low pss iler wih u o K os Fig. L. syhroous/ ohere deodulor or DSBSC sigls (i) Coss Loop his s show i Fig. L. osiss o wo ohere deeors. volge orolled osillor iiilly dused o opere he orre suppressed rrier requey,, ssued o be kow priori, supplies he lolly geered rrier o he wo ohere deeors-o oe o he direly d o he oher hrough -9 phse shier. he op os direly ro he volge orolled osillor ohere deeor reeives he (VCO). he boo bled odulor hs rrier o he or si obied by eedig he VCO oupu hrough 9 phse shier. he ioig DSBSC sigl E os is ed s he oher ipu o boh o he bled odulors. Suppose he rrier phse error is zero whih es he phse ose bewee he ioig rrier d he lolly geered rrier is zero. he he oupu o he I-hel is E d h o he Q-hel is zero. he I-hel oupu is ke s he deoduled sigl. Now uder pril siuio, here eiss iie phse ose bewee he wo rriers. he, or suh E se he I-hel produes oupu proporiol o os while h o he Q- E hel is si. Boh o hese oupus hve bee show o be ed o he phse disriior whih osiss o uliplier ollowed by low pss iler. For vlues o quie sll, we hve os d si. he low pss iler used i he phse disriior hs u o requey o he order o ew Herz, gives d volge proporiol o is oupu sie vriios i will be very slow s opred o he vriios i. hus we hve d volge h hs he se polriy s d is proporiol o i. his hges he requey o osillio o VCO i suh wy so s o lok i o, hereby keepig he phse ose wihi very sll vlues.

53 DSBSC sigl E os os Bled Modulor si -9 phse shier Bled Modulor I-hel Q-hel Low pss iler Volge orolled osillor Low pss iler E os d orol volge E si Deeor oupu Phse disriior Fig. L. Coss loop or deodulio o DSBSC sigls he Coss loop provides good pril soluio o hieve phse syhrois oo o ohere deeio. However, i suers ro oe or disdvge-he 8 phse E os we hve biguiy o he deoduled sigl. Suppose i sed o reeivig E os. he oupu o he uliplier used i he phse disriior produes oupu proporiol o E, i is isesiive o he polriy o he ioig sigl. Uder he loked odiios o he phse disriior, we re o eri bou he polriy o he deoduled sigl; wheher i is or. However, or deodulig udio sigls, his does o pose serious proble s our ers re isesiive o polriy o he deoduled sigl. For video sigls, deoduled sigl wih egive polriy reprodues ivered piure i he reeiver whih is obviously very obeioble. Siilrly, or polr d lso his phse biguiy issue would dge he d s beoes d vie-vers. he phse orol o he loop eses or he odiio o o odulio prese he ipu. However, his is o serious proble s he loop esblishes he lokup odiio very s. (ii) Squrig loop oher relizio o DSBSC deodulor is show i Fig. L.. his is kow s squrig loop.

54 DSBSC sigl E os Muliplier LPF Squre lw devie Bdpss iler ered Liier Frequey divider K Fig. L. squrig loop Sigle Sidebd Modulio Hilber rsor he Hilber rsor ie uio is obied by shiig ll requey opoes by 9. I is, hereore represeed by lier syse hvig rser uio H s show i he igure below H 9 Fig. L. rser uio or Hilber rsorer -9 We oe h he phse uio is odd. he posiive requey opoes ge -9 phse shi wheres he egive requeies udergo 9 phse shi. he syse uio is give s H sg orrespodig o ipulse respose o h he SSB sigl y be geered by pssig DSBSC oduled sigl hrough bd-pss iler o rser uio H u. Le us id ou his H u. We kow h DSBSC sigl is epressed s s E os DSBSC his is bdpss sigl oiig oly he i phse opoe. he low pss ople evelope o he DSBSC oduled sigl is give s

55 ~ s DSBSC E he SSB oduled sigl is lso bdpss sigl. However, ulike he DBSC oduled sigl, i hs qudrure s well s iphse opoe. Le he low pss sigl ~ deoe he ople evelope o s Re ~ s ep u u s u. Hee, We e proeed o id ou he low pss ople equivle ~ s u. o do so, he bdpss iler rser uio is repled by equivle low pss iler o rser uio ~ s show i Fig. Fro he Fig. we observe h H u ~ sg, H u elsewhere he DSBSC oduled sigl is repled by is ople evelope. he speru o his is ~ S E M DSBSC he desired ople evelope s u ~ ~ rsor o he produ o H S u ~ is deeried by evluig he iverse Fourier DSBSC. hus, ~ ~ E H u S DSBSC M sg Le us hve sigl ˆ suh h ˆ sg M hus, ~ E su ˆ ordigly, he heil epressio or he SSB oduled wve is E su os ˆ si his equio ells us h, eep or slig or, oduled wve oiig oly upper sidebd hs iphse opoe equl o he essge sigl d qudrure opoe equl o. ˆ, he Hilber rsor o Fro he oregoig we y oe h, whe he obeive is o rei he lower sidebd oly, he rser uio o he bdpss iler eeds o be odiied o ~ sg, H l elsewhere hus, he oupu o his bdpss iler i respose o he ople evelope o he DSBSC oduled sigl beoes ~ ~ E H l S DSBSC M sg h gives us s u

56 ~ E sl ˆ ordigly, he heil epressio or he SSB oduled wve is h ois he lower sidebd oly is E sl os ˆ si Bled Modulor os os Σ h ; Bled Modulor h si Fig. L. Phse shi ehod o geerio o SSB-SC sigl he SSB sigl s geered by Fig. L. hs wveor epressed s SSB where si h os by. h is he sigl obied by shiig he phse o eh requey opoe o (b) Wever s ehod o SSB-SC geerio

57 Bled Modulor os Bled Modulor Low pss iler u o requey Low pss iler u o requey Bled Modulor 9 Phse 9 - Phse si Shier Shier + si udio F Crrier si RF Crrier Ipu Geeror + Geeror Bled Modulor si SSB-SC Oupu Fig. L. SSBSC geerio by Wever s ehod he Wever s ehod odiies he phsig ehod o rid o he desig issues risig i widebd phse shiers. I uses udio requey sub rrier requey o. Le us id ou he epressio or he suer oupu s show i Fig. he op le bled odulor produes oupu whih is give s si os si si he low pss iler wih u o requey o rees he higher requey er give by. hereore, he oupu o he op righ bled odulor is epressed s si os si si he boo le bled odulor produes oupu whih is give s si si os os he low pss iler wih u o requey o rees he higher requey er give by. hereore, he oupu o he boo righ bled odulor is epressed s os si si si Hee, he oupu o he suig pliier beoes si si si si si si Hee, he odulor geeres he USB-SC orrespodig o rrier requey o or he LSB-SC orrespodig o rrier requey o. he Wever s ehod hs eri dvges suh s: No eed or y sidebd suppressio iler No eed or y widebd phse shier

58 s he phse shiers re desiged or sigle requey, hey re ereely siple d hep. No eed or reque duses Esy o hge ro USB-SC o LSB-SC d vie vers he suig uio oupu. Deodulio o SSB sigls C be oplished by y syhroous/ ohere kid o deodulors disussed erlier. Vesigil Sidebd Modulio his is oproise bewee he bdwidh oservig eure o ypil SSBSC odulio d deodulio sipliiy o he oveiol M sigls. his is widely used or rsiig elevisio (V) sigls oupyig speru i he VHF d UHF bd o requeies. I his or o pliude odulio, oe sidebd is ully rsied while vesige or pr o he oher sidebd is rsied. he rrier is lso rsied opleely o id he proess o deodulio or piure sigl reovery he reeiver hrough he use o siple evelope deeors. elevisio sigls he e deils o odulio or used o rsi he video sigl hrerizig V syse re ilueed by wo ors: ) he video sigl ehibis lrge bdwidh d sigii low requey oe, whih rules ou he possibiliy o usig SSB. his is beuse SSB would require ereely eesive ilerig o sepre he wo sidebds. I he presee o sigii ou o low requey oes whih re eessry o reprodue he piure sigl he reeiver, i is very diiul o suppress oe sidebd opleely s he wo sidebds re sepred ro eh oher by sll ou. Neiher DSBSC is lso useul s i requires double bdwidh. Hee VSB beoes hoie h eils he rsissio o oe sidebd opleely d he oher sidebd beig used prilly. b) he iruiry used or deodulio i he reeiver should be siple d hereore hep; his suggess he use o evelope deeio, whih requires he ddiio o rrier o he VSB oduled wve. Wih regrd o poi (), i is o be oed h lhough here is ideed bsi desire o oserve bdwidh, i oeril V brodsig he rsied sigl is o quie VSB oduled. he reso is h he rsier power levels re high, wih he resul h i would be epesive o rigidly orol he ilerig o sidebds. Ised, VSB iler is isered i eh reeiver where he power levels re low. he overll perore is he se s oveiol vesigil sidebd odulio eep or soe wsed power d bdwidh.

59 Sidebd Shpig Filer i VSB Le us reple he sidebd shpig iler by equivle ople lowpss iler o rser uio H ~ s show i Fig. he iler H ~ y be epressed s he dieree bewee ~ ~ wo opoes d s ~ H ~ H u H H u ~ H he wo opoes re desribed idividully s ollows: ~ H u s show i Fig. peris o ople low pss iler equivle o bdpss iler desiged o ree he lower sidebd opleely. ~ H show i Fig. ous or boh he geerio o vesige o he lower sidebd d he reovl o orrespodig porio ro he upper sidebd. ) he rser uio b) he rser uio We y redeie he rser uio o he shpig iler s ~ sg H elsewhere, ~ H he sigu uio requey sg d he rser uio ~ H re boh odd uios o he. Hee hey boh hve purely igiry iverse Fourier rsors. ordigly, we y irodue ew rser uio s H Q ~ sg H h hs purely rel rser uio. Le H Q ; h is h Q H Q h Q deoe he iverse Fourier rsor o hus, our equivle low pss shpig iler, i ers o he ew iler beoes, H Q elsewhere ~ H he VSB oduled sigl is ow derived i ie doi. o do so, we wrie s Re~ s ep (C)

60 where s~ is he ople evelope o s H ~. Sie s~ is he oupu o he ople low pss iler o rser uio whih is produed i respose o he ople evelope o he DSBSC oduled sigl, we y epress he speru o ~ S ~ ~ H S DSBSC We hve he ople DSBSC sigl deied s ~ S DSBSC E M hus, he oupu o he equivle shpig low pss iler is s~ s ~ S E H M ~ Q kig he iverse Fourier rsor o he bove we ge ~ s E Q I he bove, he qudrure opoe o he essge sigl Q h Q hereore, he VSB oduled sigl beoes, ro (C), s E E Q (D) os si Q is deied s s we observe, his is he desired represeio o he VSB oduled sigl oiig E vesige o he lower sidebd. he opoe is he i phse opoe o he oduled sigl d he opoe E Q is he qudrure opoe. Modulig sigl Produ Modulor E os + Σ - Moduled sigl Osillor Filer H Q -9 phse shier E Produ Modulor si

61 Fig. L. ehod o geerig VSB sigl by sidebd shpig iler he DSBSC d SSB sigls y be osidered o be wo speil ses o he VSB oduled sigl s deied i (D). I he vesigil sidebd is iresed o he widh o ull sidebd, he resulig sigl beoes DSBSC wve wih he resul h Q vishes. I, o he oher hd, he widh o he vesigil sidebd is redued o zero, he resulig sigl ˆ, beoes SSB sigl oiig he upper sidebd, wih he resul h Q where ˆ is he Hilber rsor o. Crysl osillor Video sigl ro er Video proessig ui 8.9 MHz Diode bridge odulor 8.9 MHz Dely equlizer VSB iler o e Power pliier Lier pliier Video up overer Piure rrier Crysl Osillor +8.9 MHz Frequey Muliplier Fig. L. porio o he V rsier o rsi piure sigl oly h uses low level odulio V rsier showig he use o VSB or rsissio o video sigls is illusred i Fig. L.. Qudrure Crrier Mulipleed Syse his reers o he rsissio o wo idepede bsebd sigls usig he se rrier. he bsebd sigls DSBSC odule give rrier. s wo idepede essge sigls re rsied siuleously o he se rrier ose ro eh oher i phse by 9, i is kow s qudrure rrier ulipleed odulio syse. Boh o he odulig sigls require he se ou o bdwidh or rsissio.

62 Bled Modulor E os -9 Phse Shier Bled Modulor Crrier Sigl E os E + si - Chel Fig. L 5. rsier h uilizes qudrure rrier ulipleig o rsi wo idepede essge sigls he oupu he suig uio is epressed s y E os si Boh o he oduled sigls re DSBSC sigls h require syhroous deeio he reeiver. blok shei o suh reeiver is show i Fig. L 5.. I his digr, we hve o show epliily how requey d phse syhrois is hieved bewee he rsied d he regeered rriers. However, his is lso o ipor or our se ow. Bled Modulor LPF u o requey E E os si -9 Phse Shier Bled Modulor Crrier Sigl os LPF u o requey Fig. L 5. reeiver or deeig sigls o qudrure rrier ulipleig s we y observe qudrure rrier ulipleig redues he requiree o uber o subrriers besides reduig he bdwidh required o rsi he ulipleed sigl. ypil ppliio o his shee is used i olor V rsissio wherei he olor sigls re rsied siuleously o wo idepede rriers.

63 VESIGIL SIDEBND MODULION (VSB) Fro previous leures, i is o be oed h lhough here is ideed bsi desire o oserve bdwidh, i oeril V brodsig he rsied sigl is o quie VSB oduled. he reso is h he rsier power levels re high, wih he resul h i would be epesive o rigidly orol he ilerig o sidebds. Ised, VSB iler is isered i eh reeiver where he power levels re low. he overll perore is he se s oveiol vesigil sidebd odulio eep or soe wsed power d bdwidh. Filerig o Sidebds Le he oupu ro produ odulor be epressed s u E os Le he rser uio o he bdpss iler ollowig he produ odulor be H. hus, he speru o he ilered oduled sigl h ppers he oupu o he bdpss iler beoes S U H E M M H I he bove, M deoes he speru o he essge sigl. he proble we ddress here is o desig iler rser uio required o produe oduled sigl s wih he desired sperl hrerisis suh h he origil essge sigl y be reovered ro s by ohere deeio. Cohere deeio eils he ulipliio o he ioig reeived sigl wih lolly geered rrier E ' os h is syhroous wih he rsied rrier boh i requey d phse (le us igore or he ie beig how his e syhrois is hieved). hus he reeiver kes use o oher produ odulor whose oupu beoes

64 M M H E H M E H M E S M M H E S H M E H M E S H M E H M E H M M E H U S E s v d os ' Hee, we hve H M H M E E H H M E E S S E V ' ' ' he high requey opoes o v represeed by he seod er re reoved by low pss iler h ollows he produ odulor. hus, he speru o he low pss ilered sigl oupu beoes H H M E E V ' For disorioless reproduio o he origil essge sigl he ohere deeor oupu, we require V o be sled versio o M whih urher requires h H H H = os We kow h he essge sigl hs speru suh h M is zero ouside he iervl o. Hee we eed o sisy he bove equio or vlues o i his iervl oly. s urher sipliiio, we se

65 H so h H H () We oe h s is bdpss sigl. Hee, he oil or o represeio o i i ers o is iphse s I d qudrure opoes s Q beoe s s s Q I si os We observe h, he speru o he iphse opoe is reled o he oduled sigl s elsewhere, I S S S his beoes M E H H M E H U H U S I, Fro he bove, we ge E s I Now le us deerie he qudrure opoe s Q. o do so, we irs id ou S Q whih is epressed s elsewhere, Q S S S his kes he or o Q H H M E H U H U S, lose look he bove epressio ells us h he qudrure opoe s Q be geered ro he essge sigl by pssig i hrough iler hvig rser uio give s

66 H Q Le H H, ' deoe he oupu o his iler i respose o he essge sigl qudrure opoe o he oduled sigl beoes. hus, he s Q E ' Cobiig he iphse d he qudrure opoes o he oduled sigl, we obi s E E (B) os ' si wo ipor pois re de his poi: ) he iphse opoe s I H o he bdpss iler ivolved i he geerio o he oduled sigl log s i sisies (). is opleely idepede o he rser uio b) he sperl odiiio ribued o he rser uio o he qudrure opoe s Q. s so H is oied solely he role o he qudrure opoe is oly o ierere wih he iphse opoe so s o redue or eliie power i oe o he sidebds o he oduled sigl, depedig upo he ppliio o ieres. Modulig sigl Produ Modulor E os + Σ - Moduled sigl s Osillor Filer H Q -9 phse shier ' E Produ Modulor si Fig. L 6. shei or ipleeig VSB sigl

67 Evelope Deeio o VSB plus rrier Coeril log elevisio brodsig kes use o VSB plus sizeble ou o rrier o rsi video sigl h oupies bdwidh o ypilly -5 MHz. s i is brods ype o servie, hee i represes poi-o-ulipoi ouiio. housds o reeivers eed o be low os whih lls or evelope deeio o be used i order o reover he video sigl. I is hereore o ieres o deerie he disorio irodued beuse o evelope deeor. he ipu o he evelope deeor is k os k si Q Where k is os h deeries he perege odulio. he oupu o he evelope deeor is epressed s k k = k Q kq k he righos er idies he disorio oribued by he qudrure opoe he VSB sigl. he disorio be redued by (i) reduig he perege odulio o redue k d (ii) iresig he widh o he vesigil sidebd o redue Q o Q. Boh o hese ehods re used prilly. I oeril V brodsig, he vesigil sidebd oupies widh o bou.5 MHz whih ous o bou oe-qurer o ull sidebd. his hs bee deeried epirilly s he widh o he vesigil sidebd odulio required o keep he disorio due o odulio is erly. SUPERHEERDYNE RECEIVERS Q wihi olerble liis whe he perege he oduled sigls, we lered i previous leures re ypilly deeed i rdio reeivers kow s superheerodye reeivers. Edwi rsrog iveed he oep o super heerodye reeiver i 98. reeiver is desiged o rry ou he iverse operio o rsier. Modulio is ipor rsier sigl proessig sk h is deided by hos o ors suh s he bsebd sigl ype, he hel odiios, he sipliiy d os o reeiver d he ype o ppliio or servie. Modulio o rrier by bsebd sigl is esseilly low pss o bdpss oversio h is eeed by sigl ulipliio i ie doi. Mulipliio o sigl by siusoid shis ll requeies up d dow by he requey o he siusoid. Beuse o his, sio seleio be

68 oplished by buildig ied bdpss iler d shiig he ipu requeies so h he sio o ieres lls i he pssbd o he iler. his is logous o osruig viewig widow o he requey is d ised o ovig his widow roud o view priulr porio o he is, we keep he widow siory d shi he eire is. his shiig is lled heerodyig d he resulig reeiver is lled superheerodye reeiver. ypil reeiver is show i Fig. L 7.. RF pliiers wih bd pss ilers ued o desired E os Frequey overer Lol Osillor LO IF IF pliier E os Deeor IF udio pliier Speker k Fig. L 7. superheerodye rdio reeiver brods sigls Heerodyig produes boh upwrd d dowwrd shi i requey. While oe o hese shis oves he desired sio io he IF widow (5 o 6 KHz), he oher shi oves oher sio io his se widow. his udesired sigl is lled ige d eeds o be eliied ro he reeiver. oplee bdpss syse osiss o he rsissio hel plus ued pliiers d ouplig devies oeed eh ed. Hee, he overll requey respose hs ore oplied shpe h h o sigle ued pliier. Vrious physil ees resul i loose bu sigii oeio bewee he syse s bdwidh d he rrier requey. he es i rdio syse produe sigii disorio uless he requey rge is sll opred o, oreover, desig o resobly disorioless bdpss pliier urs ou o be quie diiul i he bdwidh B is eiher very lrge or very sll opred o. s rule o hub, he riol bdwidh B should be kep wihi he rge B..

69 he bdwidh o he syse should be wihi % o % o he rrier requey. Syses desiged his wy re lled rrowbd syses. ll he ouiio syses h we see or work wih ll io his egory o rrowbd syses uless oherwise eioed. s eple, le us lise o he Cuk sio operig 97 KHz rrier requey. he lol osillor is se o = 7 KHz. Mulipliio by his siusoid ples he sio 97 KHz righ io he IF iler pssbd. Bu he sio operig 7+55 = 78 KHz lso uliplies he lol osillor requey o produe opoe 55 KHz. his ige sio would be herd righ o op o he desired sio. he seprio bewee he ige d he desired sio is wie he IF requey or 9 KHz. bdpss iler wih pssbd o less h 8 KHz would oplish he seprio. his iler us pss he desired sio, while reeig he sio 9 KHz wy. his iler eeds o be uble lso. Bu i eed o be shrp bdpss iler. sigle sge o ued irui is deque. he e reeives sigl h is weighed su o ll brods sigls. er soe ilerig o be eied ler, he ioig sigl is pliied i RF pliier. he resulig sigl is shied up d dow i requey by uliplyig by siusoidl osillor lled he lol osillor. he oupu o he heerodyer is pplied o shrp bdpss iler osisig o uliple ilerig sges. his ilerig is obied wih pliiio. he ied bd pss iler is se 55 KHz, lled he ieredie requey (IF) d hs bdwidh o KHz hig h o he sio. I os reeivers, he IF iler is de o hree ued iruis h re liged so s o geere Buerworh iler hrerisis. he oupu o he IF pliier represes oduled sigl wih ied rrier requey o 55 KHz wih pliiio d beig sepred ou ro he oher sigls. Choie o he IF requey Clerly, he IF requey us o lie i he requey bd lloed or give ouiio ppliio. For eple, oeril M uses requey bd ro KHz. hus, IF o be ke o be y vlue iside his bd. very high vlue o IF would resul i poor seleiviy d poor de-hel reeio uless shrp uo ilers re used. he ioig rdio sigl is give he dvge o ige requey reeio by he RF pliier. ll brods sigls i he sdrd M brods bd (55-65 khz) re rsled o ied requey o 55 khz by he IF pliier. he IF pliier deides os o he gi d bdwidh o he rdio reeiver. his is i, igeious obiio o pliier d bdpss iler. his is he grees dvge o superheerodye reeiver. er he sigl is pliied, i is ed o pproprie deeor. his y be oohere deeor like evelope deeor h dees DSB wih rrier ype o sigls or i y be y o he ohere deeors disussed previously. s we y observe, he origil sigl is obied he oupu o his deeor whih is power pliied (usully push pull oigurio) d delivered o he speker or reproduig he origil speeh or voie.