Qpsk Modulation And Demodulation And Frame Structure

Modem is the basic elements of the whole digital communication system and theperformance of digital communication system is influenced by modem in substance.QPSK is one of modem, which has good performance, implemented easily and has beenused in the projects widely. Basing on the flow of modem, this thesis mainly focuses onthe problems in QPSK modem and tries to solve these problems.The first part of this thesis will introduce the whole flow and principle of QPSKmodem by the model of Monte Carlo. It will put emphasis upon the method and principleof no inter-symbol interference and band-limited signal design, which includes pulseshaping filter, interpolation and decimation, low-pass filter, carrier synchronization,matched filter, frequency shift estimation, phase estimation and so on. Forming the framein the project will be also introduced. The second part of this thesis mainly introducesfrequency shift estimation and phase estimation. FFT frequency estimation is applied toFrequency shift estimation. 4096 point FFT will be programmed by VHDL on QuartusⅡ.For phase estimation, a way of getting the average of the phases of a number of symbolsis used and we try to find out how the number of symbols affects the performance of thephase estimation.