What is PSK ? | PSK Advantages| PSK Disadvantages | PSK application | Phase Shift Keying

What is PSK  ? | PSK Advantages| 

PSK Disadvantages | PSK application  

 Phase Shift Keying

What is PSK ?

It is a digital modulation technique which uses phase of the analog carrier to represent digital binary data. Phase of the carrier wave is changed according to the binary inputs (1 or 0). In two level PSK, difference of 180 phase shift is used between binary 1 and binary 0.

There are many different types of modulation techniques which utilizes this concept to transmit digital binary data. It include two level PSK (i.e. BPSK), Four level PSK (i.e. QPSK) etc. Some techniques employ both amplitude and phase variation to represent binary data such as 16-QAM, 64-QAM, 256-QAM etc. Two level PSK represents single bit by each signaling elements while four level PSK represents two bits by each signaling elements and so on. 8-PSK represents three bits by each signaling elements.

Following are the equations used to represent BPSK.
➨s(t) = A*cos(2*π*fc*t) for Binary 1 than
➨s(t) = A*cos(2*π*fc*t + π) for Binary 0


PSK is of two types, depending upon the phases the signal gets shifted. They are −

1. BPSK (Binary Phase Shift Keying BPSK )

  
This is also called as 2-phase PSK or Phase Reversal Keying. In this technique, the sine wave carrier takes two phase reversals such as 0° and 180°.

BPSK is basically a Double Side Band Suppressed Carrier DSBSC modulation scheme, for message being the digital information.



2. QPSK (Quadrature Phase Shift Keying QPSK)

This is the phase shift keying technique, in which the sine wave carrier takes four phase reversals such as 0°, 90°, 180°, and 270°.

If this kind of techniques are further extended, PSK can be done by eight or sixteen values also, depending upon the requirement.

Following are the benefits or advantages of PSK:

➨It carries data over RF signal more efficiently compare to other modulation types. Hence it is more power efficient modulation technique compare to ASK and FSK.
➨It is less susceptible to errors compare to ASK modulation and occupies same bandwidth as ASK.
➨Higher data rate of transmission can be achieved using high level of PSK modulations such as QPSK (represents 2 bits per constellation), 16-QAM (represents 4 bits per constellation) etc.

Following are the disadvantages of PSK:

➨It has lower bandwidth efficiency.
➨The binary data is decoded by estimation of phase states of the signal. These detection and recovery algorithms are very complex.
➨Multi-level PSK modulation schemes (QPSK, 16QAM etc.) are more sensitive to phase variations.
➨It is also one form of FSK and hence it also offers lower bandwidth efficiency compare to ASK modulation type.

PSK application 

Phase Shift Keying PSK is the digital modulation technique in which the phase of the carrier signal is changed by varying the sine and cosine inputs at a particular time. PSK technique is widely used for wireless LANs, bio-metric, contactless operations, along with RFID and Bluetooth communications.