Phase Shift Keying (PSK) - Digital To Analog Conversion and Transmission Tutorials Part IV

Phase Shift Keying (PSK) - Basic Tutorials

We vary the phase shift of the carrier signal to represent digital data.
The bandwidth requirement, B is:
B = (1+d)xS 

PSK is much more robust than ASK as it is not that vulnerable to noise, which changes amplitude of the signal.

Binary phase shift keying(See Diagram Above)

Further Reading suggested :

Digital To Analog Conversion and Transmission Tutorials

Amplitude Shift Keying (ASK)

Frequency Shift Keying (FSK)
Constellation Diagrams

Implementation of BASK



Quadrature PSK
To increase the bit rate, we can code 2 or more bits onto one signal element.

In QPSK, we parallelise 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.
nThe two PSKed signals are then added to produce one of 4 signal elements. L = 4 here.

QPSK and its implementation




Problem Example - 1

Find the bandwidth for a signal transmitting at 12 Mbps for QPSK. The value of d = 0.

Solution

For QPSK, 2 bits is carried by one signal element. This means that r = 2. So the signal rate (baud rate) is S = N × (1/r) = 6 Mbaud. With a value of d = 0, we have B = S = 6 MHz.