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MATLAB Code for QPSK Modulation and Demodulation

 

Quadrature Phase Shift Keying (QPSK) is a digital modulation scheme that conveys two bits per symbol by changing the phase of the carrier signal. Each pair of bits is mapped to one of four possible phase shifts: 0°, 90°, 180°, or 270°

00  ===> 0 degree phase shift of carrier signal

01  ===> 90 degree

11  ===> 180 degree

10  ===> 270 degree

 

MATLAB Script


 

Result

data
1
0
2
2
0
2
1
.
.
.

modData
-1.00000000000000 + 1.22464679914735e-16i
-1.83697019872103e-16 - 1.00000000000000i
1.00000000000000 + 0.00000000000000i
6.12323399573677e-17 + 1.00000000000000i
6.12323399573677e-17 + 1.00000000000000i
-1.83697019872103e-16 - 1.00000000000000i
1.00000000000000 + 0.00000000000000i
-1.00000000000000 + 1.22464679914735e-16i
6.12323399573677e-17 + 1.00000000000000i
-1.83697019872103e-16 - 1.00000000000000i
.
.
.


Fig 1: Constellation Diagram of Transmitted QPSK (or 4 PSK) Signal




Fig 2: Constellation Diagram of Received QPSK (or 4 PSK) Signal through Noisy Channel


Further Reading

  1. MATLAB Code for Constellation Diagram of QPSK
  2. Constellation Diagram of BPSK

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