ECE5713 : Advanced Digital Communications. Concept of a constellation diagram. Digital Modulation Schemes. Bandpass Modulation MPSK MASK, OOK MFSK

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1 ECE5713 : Advaned Dgtal Communaton In-phae and Quadrature (I&Q) Repreentaton Bandpa Modulaton MPSK MASK, OOK MFSK Any bandpa gnal an alo be repreented a ( = x( o( ω 0t ) y( n( ω 0t ) x( a real-valued gnal alled In-phae (I) y( a real-valued gnal alled Quadrature (Q) Th often a onvenent form whh Emphaze the fat that two gnal may be tranmtted wthn the ame bandwdth Cloely parallel the phyal mplementaton of the Tx/Rx 04-May-15 Advaned Dgtal Communaton, Sprng-2015, Week May-15 Advaned Dgtal Communaton, Sprng-2015, Week-8 2 Conept of a ontellaton dagram Dgtal Modulaton Sheme Ba Dgtal Modulaton Sheme: Ampltude Shft Keyng (ASK) Frequeny Shft Keyng (FSK) Phae Shft Keyng (PSK) Ampltude Phae Keyng (APK) For Bnary gnal (M = 2), we have Bnary Ampltude Shft Keyng (BASK) Bnary Phae Shft Keyng (BPSK) Bnary Frequeny Shft Keyng (BFSK) For M > 2, many varaton of the above tehnque ext uually lafed a M-ary Modulaton/deteton 04-May-15 Advaned Dgtal Communaton, Sprng-2015, Week May-15 Advaned Dgtal Communaton, Sprng-2015, Week-8 4

2 Bandpa MOdulaton and DEModulaton Overvew of Modulaton Sheme 04-May-15 Advaned Dgtal Communaton, Sprng-2015, Week-8 5 dgtal modulaton, (a) PSK (b) FSK () ASK (d) ASK/PSK (APK) 04-May-15 Advaned Dgtal Communaton, Sprng-2015, Week-8 6 Modulaton Proe Ampltude Shft Keyng In Ampltude Shft Keyng (ASK), the ampltude of the arrer wthed between two (or more) level aordng to the dgtal data For BASK (alo alled ON-OFF Keyng (OOK)), one and zero are repreented by two ampltude level A 1 and A 0 Analytal Expreon: ( = A o( ω, 0 t T where A = peak ampltude Ampltude Shft Keyng 2 ( = Ao( ω 0 = 2Arm o( ω0 = 2A o( ω0 = 2E E 2 P o( ω 0 = o( ω 0 T Hene, 2E ( ( = o( ω 0, T 0 t T, = 1,2,... M where T 2 E = ( dt, = 0,2,... M 0 rm 1 04-May-15 Advaned Dgtal Communaton, Sprng-2015, Week May-15 Advaned Dgtal Communaton, Sprng-2015, Week-8 8

3 Ampltude Shft Keyng Where for bnary ASK (alo known a ON OFF Keyng (OOK)) 1( = Am( o( ω t + φ ), 0 t T bnary 1 0 ( = 0, 0 t T bnary 0 Mathematal ASK Sgnal Repreentaton The omplex envelope of an ASK gnal : g( = A m( The magntude and phae of an ASK gnal are: A( = Am(, φ ( = 0 The n-phae and quadrature omponent are: x( = A m( y( = 0, the quadrature omponent wated. 04-May-15 Advaned Dgtal Communaton, Sprng-2015, Week-8 9 ASK, OOK, MASK The ampltude (or hegh of the ne wave vare to tranmt the one and zero One ampltude enode a 0 whle another ampltude enode a 1 (a form of ampltude modulaton) 04-May-15 Advaned Dgtal Communaton, Sprng-2015, Week-8 10 Implementaton of bnary ASK OOK and MASK OOK (On-OFF Key) 0 lene. Senor network: battery lfe, mple mplementaton MASK: multple ampltude level 04-May-15 Advaned Dgtal Communaton, Sprng-2015, Week May-15 Advaned Dgtal Communaton, Sprng-2015, Week-8 12

4 Pro Con Pro, Con and Applaton Smple mplementaton Major dadvantage that telephone lne are very ueptble to varaton n tranmon qualty that an affet ampltude Sueptble to udden gan hange Ineffent modulaton tehnque for data Applaton On voe-grade lne, ued up to 1200 bp Ued to tranmt dgtal data over optal fber More ode Laer tranmtter 04-May-15 Advaned Dgtal Communaton, Sprng-2015, Week-8 13 Detetor for ASK: Coherent Reever Coherent deteton requre the phae nformaton A oherent detetor mxe the nomng gnal wth a loally generated arrer referene Multplyng the reeved gnal r( by the reever loal ollator (ay A o(w ) yeld a gnal wth a baeband omponent plu a omponent at 2f Pang th gnal through a low pa flter elmnate the hgh frequeny omponent In prate an ntegrator ued a the LPF 04-May-15 Advaned Dgtal Communaton, Sprng-2015, Week-8 14 Nonoherent Reever The output of the LPF ampled one per bt perod Th ample z(t) appled to a deon rule z(t) alled the deon tatt Mathed flter reever of OOK gnal Doe not requre a phae referene at the reever If we do not know the phae and frequeny of the arrer, we an ue a nonoherent reever to reover ASK gnal Envelope Detetor: A MF par uh a the root raed one flter an thu be ued to hape the oure and reeved baeband ymbol In fat th a very ommon approah n gnal deteton n mot bandpa data modem 04-May-15 Advaned Dgtal Communaton, Sprng-2015, Week-8 15 The mplet mplementaton of an envelope detetor ompre a dode retfer and moothng flter 04-May-15 Advaned Dgtal Communaton, Sprng-2015, Week-8 16

5 Frequeny Shft Keyng (FSK) In FSK, the ntantaneou arrer frequeny wthed between 2 or more level aordng to the baeband dgtal data data bt elet a arrer at one of two frequene the data enoded n the frequeny In the pat, FSK ha been the mot wdely ued form of dgtal modulaton;why? Smple both to generate and detet Inentve to ampltude flutuaton n the hannel FSK onvey the data ung dtnt arrer frequene to repreent ymbol tate An mportant property of FSK that the ampltude of the modulated wave ontant Waveform 04-May-15 Advaned Dgtal Communaton, Sprng-2015, Week-8 17 Analytal Expreon 2 E ( t ) = o( t + ), = 0,1,... M 1 T 1 ω 23 φ t θ ( ) [ ( ) ] t = ω0t + ωd m τ dτ Analog form d f ( ) ( ) = θ t = f0 + fdm t dt General expreon 2 E ( t ) = o( 2πf 0t + 2π ft ), = 0,1,... M 1 T Where f = f f f = f + f and E = ke, T = kt May-15 Advaned Dgtal Communaton, Sprng-2015, Week-8 18 b b Frequeny Shft Keyng One frequeny enode a 0 whle another frequeny enode a 1 (a form of frequeny modulaton) Multple Frequeny-Shft Keyng (MFSK) More than two frequene are ued More bandwdth effent but more ueptble to error ( t ) A o 2π f t = 1 M ( t ) = ( 2πf ( 2πf Ao 1 Ao 2 bnary 1 bnary 0 Repreent eah logal value wth another frequeny (lke FM) 04-May-15 Advaned Dgtal Communaton, Sprng-2015, Week-8 19 f = f + (2 1 M)f d f = the arrer frequeny f d = the dfferene frequeny M = number of dfferent gnal element = 2 L L = number of bt per gnal element 04-May-15 Advaned Dgtal Communaton, Sprng-2015, Week-8 20

6 Phae Shft Keyng One phae hange enode a 0 whle another phae hange enode a 1 (a form of phae modulaton) DBPSK, QPSK Dfferental BPSK 0 = ame phae a lat gnal element 1 = 180º hft from lat gnal element ( t ) o ( 2πf ( π f t +π ) A = A o 2 04-May-15 Advaned Dgtal Communaton, Sprng-2015, Week-8 21 bnary 1 bnary 0 Four Level: QPSK ( t ) = π A o 2 π f t π A o 2 π f t π A o 2 π f t 00 4 π A o 2 π f t May-15 Advaned Dgtal Communaton, Sprng-2015, Week-8 22 QPSK Example FSK V PSK 04-May-15 Advaned Dgtal Communaton, Sprng-2015, Week May-15 Advaned Dgtal Communaton, Sprng-2015, Week-8 24

7 PSK BPSK 04-May-15 Advaned Dgtal Communaton, Sprng-2015, Week May-15 Advaned Dgtal Communaton, Sprng-2015, Week-8 26 BPSK Detetor M=4 QPSK 04-May-15 Advaned Dgtal Communaton, Sprng-2015, Week May-15 Advaned Dgtal Communaton, Sprng-2015, Week-8 28

8 QPSK QPSK Deteton 04-May-15 Advaned Dgtal Communaton, Sprng-2015, Week May-15 Advaned Dgtal Communaton, Sprng-2015, Week-8 30 QPSK Deteton: Mathed Flter MPSK 04-May-15 Advaned Dgtal Communaton, Sprng-2015, Week May-15 Advaned Dgtal Communaton, Sprng-2015, Week-8 32

9 MPSK MPSK Deteton 04-May-15 Advaned Dgtal Communaton, Sprng-2015, Week May-15 Advaned Dgtal Communaton, Sprng-2015, Week-8 34 Mathed flter deteton Properte of MPSK Contellaton In tme doman, all M gnal have the ame ampltude. All M gnal have the ame energy. All M ontellaton pont are the ame dtane from the orgn -- they are equally paed on a rle They dffer n phae only (.e. the data enoded n the phae of the tranmtted arrer). Eah phae dffer by 2p/M radan. 04-May-15 Advaned Dgtal Communaton, Sprng-2015, Week May-15 Advaned Dgtal Communaton, Sprng-2015, Week-8 36