.¦Ð/4-dqpsk Baseband Communication System Design And Simulation

With the rapid development of the software radio technology and the digital signal processing technology, all-digital modulation and demodulation technology has been widely applied. Because of its own advantages,π/4-DQPSK modem is better than QPSK and OQPSK in the performance. For instance, it possesses features of applicability to noncoherent detection and fast synchronization. So its anti-fading performance is better than many other modems. And the system designed is more convenient than common ones.The communication system ofπ/4-DQPSK modem has been researched in this dissertation. Firstly,π/4-DQPSK modem is compared to QPSK modem and OQPSK modem. Then its significant advantage and the reason why it has been widely used are pointed out.After the basic principle ofπ/4-DQPSK modulation and demodulation has been introduced. The simulation ofπ/4-DQPSK modulation and demodulation has been finished with MATLAB. The BER performance ofπ/4-DQPSK under AWGN environment has been got. The design is proved to be right by contrast with the theoretical curve.Secondly, the modules of the system have been designed with FPGA. Such as interpolators, extractors, filters and NCO are included. And the implementation diagram and the simulation waveform are shown. So the design is more close with hardware.At last, the complete design of the system are achieved under System Generator, according to the result of the debugging the design is proved to be rational.