Research And Realization Of Analysis And Demodulation Of GMSK In Burst Communication System

With the continuous development of the Communication Technology in recent years, requirements on communication systems becomes higher and higher. Modern communication technology with larger capacity, longer distance and higher quality is researched by more and more researchers. Taking the contradiction between the limited spectrum and the need for high information capacity into consideration, technology of modulation in the future should have the advantages as follow: 1.better spectrum characteristics; 2.better bandwidth efficiency. Gaussian Minimum Shifting Keying, namely GMSK, as a special type of Constant Phase Modulation, has constant envelope and continuous phase characteristics, and its spectrum efficiency is much better than other CPM signals with the appearance of Gaussian Filter. With the decrease of the Bb Tb parameter, it performs better on both of the spectrum and bandwidth efficiency. The study of the demodulation technology for GMSK signals, especially for those with extremely low BbTb parameter, plays a significant role in the research of communication system with high data rate and limited bandwidth.The thesis mainly studies the analysis and demodulation technology for GMSK signals with low BT parameter. FPGA implementations is also discussed, as well as the analysis of signals and key technologies of demodulation. Taking both complexity and performance of the algorithms into consideration, the thesis finally presents a frame of non-coherent receiver for burst GMSK signals with low BbTb parameter, and then proves the frame of the receiver is feasible by FPGA implementation.Firstly, existing algorithms are developed concerning to the severer inter symbol interference and longer partial response length of the GMSK signals with the Bb Tb parameter becomes much lower. Thus, the problem of the parameter estimation of the burst signals could be solved.Secondly, the thesis studies the technology of both coherent and non-coherent demodulation, and compares the BER performance of the different algorithms mentioned. Taking the complexity of the a algorithm, the BER performance and the feasibility of the receiver into consideration, the receiver is designed with the algorithm of one bit differential detection with Viterbi Decode. Afterwards, technology of timing recovery and synchronization for burst signals is also discussed in this thesis.Finally, the thesis divides the frame of the non-coherent receiver for burst GMSK signals with extremely low BbTb parameter into several parts, based on the analysis on the theory of parameter estimation, synchronization and technology of demodulation. Each part of the receiver has been realized on FPGA, and the results are shown in the thesis. Finally, the design of the non-coherent receiver is accomplished on FPGA through hardware debugging, thus burst GMSK signals with extremely low BT parameter could be demodulated successfully.