QPSK signal generation in Matlab

QPSK modulation is a widely used digital modulation technique. It is a bandwidth efficient scheme because it allows to transmit two bits per symbol. Bandwidth efficient means that more information bits can be transmitted for a given allocated bandwidth. In this article the QPSK modulation is explained with the help of Matlab.

In this QPSK signal generation in Matlab tutorial you will learn how to write matlab code to generate QPSK signal.

The mathematical form of QPSK signal is-

$\large&space;s(t)=\begin{cases}Acos(2\pi&space;f_ct-\frac{3\pi}{4})&space;&&space;dibit\space&space;00\\Acos(2\pi&space;f_ct-\frac{\pi}{4})&space;&&space;dibit\space10\\Acos(2\pi&space;f_ct+\frac{\pi}{4})&space;&&space;dibit\space01\\Acos(2\pi&space;f_ct+\frac{3\pi}{4})&space;&&space;dibit\space&space;11&space;\end{cases}$

where, $0\leq&space;t\leq&space;T$ and T is the symbol duration

The QPSK signal can also be written in the following compact form,

$\large&space;s(t)=Acos(2\pi&space;f_ct+\phi&space;(t))$

where,

$\large&space;\phi(t)=\begin{cases}-\frac{3\pi}{4}&space;&&space;dibit\space00\\-\frac{\pi}{4}&space;&&space;dibit\space10\\+\frac{\pi}{4}&space;&&space;dibit\space01\\+\frac{3\pi}{4}&space;&&space;dibit\space11&space;\end{cases}$

Matlab Code for QPSK signal generation in Matlab

The matlab code to generate these four QPSK signal is below:

The Graph of QPSK signal in Matlab is shown below.

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