Digital Transmission Via Carrier Modulation Carrier Phase Modulation BPSK(Binary PSK):M=2 QPSK(Quadrature PSK):M=4 MPSK(M-ary PSK):M>2
Digital Transmission Via Carrier Modulation Carrier Phase Modulation BPSK(Binary PSK) : M=2 QPSK(Quadrature PSK): M=4 MPSK(M-ary PSK): M > 2
Carrier Phase Modulation Carrier phase is used to transmit digital information via digital phase modulation M-ary phase modulation (M=2k) 2πm m=0,1,M-1 M Binary phase modulation(M=2) ■0=0,0=元 M carrier phase modulated signal waveform 0=g,0c2x+2m=0L-1 Transmitting filter pulse shape Amplitude
Carrier Phase Modulation ◼ Carrier phase is used to transmit digital information via digital phase modulation ◼ M-ary phase modulation (M=2k ) ◼ ◼ Binary phase modulation (M=2) ◼ ◼ M carrier phase modulated signal waveform ◼ 2 m , 0,1,., 1 m m M M = = − 0 0 = = 0, 2 m T c ( ) ( )cos(2 ), 0,1,., 1 m u t Ag t f t m M M = + = − Transmitting filter pulse shape Amplitude
PSK(Phase Shift Keying) Digital phase modulation is called PSK PSK signals have equal energy See Figure 6.7 page 289 ■5n=」o)dt=于」gudh=5,for all m Normalized power case(Rectangular g(t)) ·80=27,0≤1≤T今)g0d=1→A= Constant envelope
PSK(Phase Shift Keying) ◼ Digital phase modulation is called PSK ◼ PSK signals have equal energy ◼ See Figure 6.7 page 289 ◼ ◼ Normalized power case (Rectangular gT (t)) ◼ → → ◼ 2 2 2 ( ) ( ) , 2 m m T s A u t dt g t dt for all m − − = = 1 2 ( ) 1 2 g t dt T − = A = s g t T t T T ( ) 2 , 0 = 2 2 ( ) cos(2 ), 0,1,., 1 s m c m u t f t m M T M = + = − Constant envelope
PSK with 2 orthogonal basis Changing representation of waveform 2πm u (t)=Agr(t)cos(2ft+ M -5(tco2fo)-in(2r)sin -cot(codim-gx()in2x M0 45(t) ms Two orthogonal basis:v(),v() PSK can be represented geometrically as two- dimensional with components SDe,5s
PSK with 2 orthogonal basis ◼ Changing representation of waveform ◼ Two orthogonal basis: ◼ PSK can be represented geometrically as twodimensional with components 2 ( ) ( ) cos(2 ) 2 2 ( ){cos(2 ) cos( ) sin(2 )sin( )} 2 2 cos( ){ ( ) cos(2 )} sin( ){ ( )sin(2 )} m T c s T c c s T c s T c m u t Ag t f t M m m g t f t f t M M m m g t f t g t f t M M = + = − = + − mc s ms s 1 ( )t 2 ( )t 1 2 ( ), ( ) t t , mc ms s s
Constellation of PSK Two dimensional =6)-(W5cs2W5m20 M=2 M=4 M=8 001 000 √50了 (5,0) 10 100 +10 Same as binary PAM with antipodal signals Why Gray code is used
Constellation of PSK ◼ Two dimensional ◼ 2 2 ( , ) ( cos , sin ) m mc ms s s m m s s s M M = = ( ,0) s ( ,0) − s M=2 Same as binary PAM with antipodal signals s M=4 01 00 11 10 s M=8 011 001 111 101 000 100 110 010 Why Gray code is used ?