QPSK Simulink Implementation

Jul 14, 2025#数字通信 #MATLAB5

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The document discusses the implementation of QPSK (Quadrature Phase Shift Keying) in Simulink, focusing on both the modulation and demodulation processes. ### Modulation Section - **Overall Framework**: Introduces the structure of the QPSK system. - **Module Parameters**: Details parameters for components like the raised cosine filter, which has a roll-off factor of 1. - **Waveforms**: Describes various stages of waveforms in the modulation process. - **Buffer and Demux**: Discusses the buffer and demultiplexer functionalities. - **Raised Cosine Transmit Filter**: Highlights the importance of this filter in the transmission process. - **Power Spectral Density**: Analyzes the power spectral density of the QPSK signal. ### Demodulation Section - Assumes carrier synchronization after passing through an AWGN (Additive White Gaussian Noise) channel. - **Module Parameters**: Lists parameters for demodulation modules. - **Carrier Module and Pulse Generator**: Explains the role of these components, noting that data rate is halved due to serial-to-parallel conversion. - **Waveforms**: Shows how the initial signal aligns with the demodulated output after a delay, confirming successful QPSK modulation and demodulation.

1 Modulation Section#

1.1 Overall Framework#

1.2 Module Parameters#

The roll-off factor of the raised cosine filter is 1

Single and Double Polarity Conversion

1.3 Waveforms of Each Stage#

1.4 Buffer#

1.5 Demux#

1.6 Raised Cosine Transmit Filter#

1.7 QPSK Signal Power Spectral Density#

2 Demodulation Section#

After passing through the AWGN channel, it is assumed that carrier synchronization has been performed

2.1 Partial Module Parameters#

2.2 Carrier Module#

2.3 Pulse Generator#

Due to serial-to-parallel conversion, the data rate is halved

2.4 Partial Waveforms#

After delaying the initial signal for a certain period, it aligns well with the demodulated output signal on the oscilloscope, indicating that QPSK modulation and demodulation have been basically achieved