Development of qpsk modulated signal transmitter and implementation in fpga
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Date
2017-06
Authors
Chia, Wei Jian
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Abstract
Digital modulation is a technique widely applies in communication application nowadays. There are three main types of digital modulation which are ASK, FSK and PSK. QPSK is a type of digital modulation which falls in categories of PSK. One of the digital modulation schemes being used in today’s communication technology is QPSK. Applications of QPSK modulator are apply in the Bluetooth, satellite communication and OFDM technologies. Most of the real works that uses the QPSK modulations are based on a specific integrated circuit. This project shows the implementation of QPSK signal modulator on FPGA using VHDL language. The QPSK modulator is divided into 3 main parts which are the DDS sine wave generator, serial to parallel converter and phase shifter. The design of the QPSK modulator signal used the Q and I approach. The DDS concept is used to generate sinusoidal signal for local oscillator of the QPSK modulator. The design is first simulated with Matlab/Simulink software prior the development of VHDL coding. Unlike other research work, the development of VHDL coding in this project is not using Altera DSP Builder Tools. The functional simulation of the QPSK signal modulation is done by using the ModelSim-Altera software. Then, the functional simulation the VHDL code is loaded to the Altera DE1 Development and Education board using Quartus II software. Lastly, the 8 bits output from the Altera DE1 Development and Education board is connected to DAC to obtain a desired analogue signal. The result is verified by comparing the input bit with the output modulated signals using oscilloscope.