Coherent PhaseShift Keying

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Coherent Phase-Shift Keying

• Binary PSK
• QPSK
• M-ary PSK

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Binary Phase-Shift Keying
and
is defined by
The pair of signals
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Binary Phase-Shift Keying
There is only one basis function of unit energy
Express the transmitted signals in terms of
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Binary Phase-Shift Keying
The coordinates of the massage points are
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Binary Phase-Shift Keying
Signal-space diagram for coherent binary PSK,
assume
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Error Probability of Binary PSK
The set of points closet to massage point 1 at
The set of points closet to massage point 1 at
Symbol 1 or
is described by
is related to the received signal
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Error Probability of Binary PSK
The conditional probability density function
that symbol 0 is transmitted is defined by
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Error Probability of Binary PSK
The conditional probability in favor of symbol
1 was transmitted symbol 0 is
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Error Probability of Binary PSK
Set
Bit error rate for coherent binary PSK
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Generation and Detection of Coherent Binary PSK
Signals

• binary PSK transmitter
• coherent binary PSK receiver

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Quadriphase-Shift Keying
The phase of the carrier takes on
i 1, 2, 3, 4
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Signal-Space Diagram of QPSK
Simplify
Quadrature carriers
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Signal-space characterization of QPSK
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Signal-Space Diagram
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Error Probability of QPSK
Symbol error rate
Bit error rate
The same bit error rate as PSK, but half the
channel bandwidth
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Generation of Coherent QPSK Signals
QPSK transmitter
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Detection of Coherent QPSK Signals
coherent QPSK receiver
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Possible Paths of QPSK
The carrier phase changes by
degrees when
both the in-phase and quadrature components of
QPSK signal changes sign. ex01-gt10
The carrier phase changes by
degrees when
the in-phase or quadrature component of QPSK
signal changes sign. ex11-gt10
The carrier phase is unchanged when neither the
in-phase nor quadrature component of QPSK changes
sign. ex10-gt10
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Offset QPSK
Reduce the extent of amplitude fluctuations when
the 180- and 90-degree shifts in carrier phase
and reduce symbol errors.
The two basis functions of offset QPSK
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Possible paths for switching
(a)QPSK (b)offset QPSK
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p/ 4-Shifted QPSK
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p/ 4-Shifted QPSK
The phase transitions from one symbol to the next
are restricted to and
radians. Consequently, envelope variations are
reduced, compared with QPSK
-shifted QPSK can be noncoherently detected, we
should really speak of -shifted DQPSK
The symbol pair (I,Q) is
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Correspondence between input dibit and phase
change
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p/ 4-Shifted DQPSK results
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M-ary PSK
One of the M possible signals
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Octaphase-Shift-Keying (M8)
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Octaphase-Shift-Keying (M8)
symbol error rate