11
PSK
–
phase of carrier signal is varied to represent binary 1 or 0
peak amplitude & freq. remain constant during each bit interval
example
:
binary 1 = 0º phase, binary 0 = 180º (
rad) phase
PSK is equivalent to multiplying carrier signal by +1 when the
information is 1, and by 1 when the information is 0
demodulation
:
demodulator must determine the phase of received
sinusoid with respect to some reference phase
advantage
:
PSK is less susceptible to errors than ASK, while it
requires/occupies the same bandwidth as ASK
more efficient use of bandwidth (higher datarate)
are possible, compared to FSK !!!
disadvantage
:
more complex signal detection / recovery process,
than in ASK and FSK
0
binary
),
t
f
Acos(2
1
binary
t),
f
Acos(2
s(t)
c
c
π
π
π
Modulation of Digital Data:
PSK
2PSK, or
Binary PSK
,
since only 2
different phases
are used.
+A
A
0
binary
t),
f
Acos(2

1
binary
t),
f
Acos(2
s(t)
c
c
π
π
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