Phase-shift keying (PSK) is a digital modulation technique that conveys data by changing the phase of a carrier wave. There are several types of PSK including binary PSK (BPSK) and quadrature PSK (QPSK). BPSK uses two phases separated by 180 degrees to transmit 1 bit per symbol, while QPSK uses four phases separated by 90 degrees to transmit 2 bits per symbol for higher data rates. PSK has advantages like more efficient data transmission compared to frequency-shift keying. However, it is non-coherent and more prone to incorrect demodulations. PSK finds applications in optical communications, local oscillators, and delay-and-add demodulation.

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.
 A digital modulation scheme that conveys data by chang
ing the phase of a carrier wave.
 It can
either determine the absolute phase relative to the unm
odulated carrier or reference signal or the change in pha
se.
 The number of
different phases used determines the amount of data th
at can be transmitted in each cycle.

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 90o 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