Design And Realization Of OQPSK Demodulation

The thesis centers on the design and implementation of OQPSK signal demodulation module required by the National Significant Scientific Apparatus Development Project(2012YQ20022404)“The Research and Implementation on High Performance Spectrum Analyzer” aiming at accurately demodulating OQPSK signal.The specific contents are as follows:Firstly,design and implement the OQPSK timing synchronization scheme.In this thesis,considered the characteristics of OQPSK signals,to tackle the inaccuracy problem in open-loop algorithm and slow convergence problem in closed-loop algorithm in the OQPSK timing synchronization process.The algorithm combined open-loop maximum average power with closed-loop I/Q-GAD is adopted to realize the fast and accurate OQPSK signal timing synchronization.Secondly,design and implement the carrier frequency offset estimation of OQPSK signals.To meet the requirements of accuracy in demodulation,the algorithm with high accuracy,proper complexity and sufficient estimation range is utilized to realize the coarse-fine frequency offset estimation.The FFT algorithm is used to coarsely estimate the frequency so that the complexity of subsequent process can be reduced and the weighted phase histogram algorithm is combined to finely estimate the frequency offset.Especially,classification estimation method is used that the range of estimation can be gradually decreased so that the frequency offset estimation accuracy can be guaranteed.Thirdly,design and implement the estimation of OQPSK carrier phase offset.By studying the typical M-power phase offset algorithm and the phase offset direct decision algorithm,the M-power phase offset estimation algorithm which is easier to be realized is selected to achieve the preliminary estimation of phase offset.In order to eliminate the influences of inter-segment phase angle jump in burst and multi-segment data demodulation,by cancellating the residual frequency and correcting the phase angle jump after conducting the actual phase interval trasition aiming at estimating phase offset precisely.Finally,implementation and test of OQPSK demodulation system.According to the requirement of the project,utilizing C language to realize OQPSK signal demodulation test and analysis module and buliting the test environment.The system performance is manifested through processing real-time OQPSK data.And the test results show that the test parameters of this system are compared with the Agilent 89600,and the key indicators are close to that of Agilent 89600 software in the same conditions.