Phase shift keying(PSK)

Phase shift keying(PSK)

1. PRESENTED BY:
DINESHKUMAR.S
E.C.E. –THIRD YEAR

2. Contents:
•Introduction
•Types
•Advantages
•Disadvantages
•Applications

3. Introduction
Phase-shift keying (PSK) is a method of digital
communication in which the phase of a transmitted
signal is varied to convey information.
There are several methods that can be used to
accomplish PSK.
Adigitalmodulationschemethatconveysdatabychang
ingthephaseofacarrierwave.
It can
eitherdeterminetheabsolutephaserelativetotheunm
odulatedcarrierorreferencesignalorthechangeinpha
se.
Thenumberof
differentphasesuseddeterminestheamountofdatath
atcanbetransmittedineachcycle.

4. Types....
•Binary Phase Shift Keying (BPSK)
•Quadrature Phase Shift Keying (QPSK)

5. Forms of phase shift keying
•PSK -Phase Shift Keying
•BPSK -Binary Phase Shift Keying
•QPSK -Quadrature Phase Shift Keying
•O-QPSK -Offset Quadrature Phase Shift Keying
•8 PSK -8 Point Phase Shift Keying
•16 PSK -16 Point Phase Shift Keying
•QAM -Quadrature Amplitude Modulation
•16 QAM -16 Point Quadrature Amplitude Modulation
•64 QAM -64 Point Quadrature Amplitude Modulation
•MSK -Minimum Shift Keying
•GMSK -Gaussian filtered Minimum Shift Keying

6. Binary Phase Shift Keying (BPSK)
•BPSK also sometimes called PRK, Phase Reversal
Keying, or 2PSK.It is the simplest form of phase shift
keying (PSK).
•It uses two phases which are separated by 180 degrees
and so can also be termed 2-PSK. It does not
particularly matter exactly where the constellation points
are positioned and in this figure they are shown on the
real axis, at 0 degrees and 180 degrees.
•This modulation is the most robust of all the PSKs since
it takes the highest level of noise or distortion to make
the demodulator reach an incorrect decision.
•It is, however, only able to modulate at 1 bit/symbol and
so is unsuitable for high data-rate applications.

7. Binary phase shift keying implementation

8. Quadrature Phase Shift Keying (QPSK)
•To increase the bit rate, we can code 2 or more bits onto
one signal element.
•In QPSK, we parallelize the bit stream so that every two
incoming bits are split up and PSK a carrier frequency.
One carrier frequency is phase shifted 90
o
from the other
in quadrature.
•The two PSK signals are then added to produce one of 4
signal elements.

9. QPSK and its implementation

10. Three constellation diagrams

11. Advantages
•It allows data to be carried along a radio
communications signal much more efficiently
than with frequent shift keying.
•Quadrature phase shift keying is another form
of data transport where four phase states are
used, all within 90 degrees of one another.

12. Disadvantages
•It is non-coherent reference signal.
•It produces more incorrect demodulations because the
error can integrate with time since the reference signal
for demodulation is not fixed.

13. Applications
•Optical communications
•Local oscillator
•Delay-and-add demodulator
•Nonlinear effects for WDM-transmission
•Multi-channel WDM