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Optical Modulators and Modulation Schemes 175
π/2
π 0
3π/2
Figure 4.44 BPSK constellation diagram.
‘00’ ‘01’ ‘11’ ‘10’
A A A A
0 t 0 t 0 t 0 t
–A –A –A –A
0 π/2 π 3π/2
Figure 4.45 QPSK symbols.
01
11 00
10
Figure 4.46 Constellation diagram of QPSK.
M-PSK signal in an interval kT ≤ t ≤ (k + 1)T may be written as
s s
s (t)= Ap(t) cos [2f t + k m (t)+ ], (4.108)
j c p j 0
where
2(j − 1)
k m (t)= , j = 1, 2, … , M (4.109)
p j
M
and is a phase constant.
0
