The Research On Digital Receiver Technology Based On Software-Defined-Radio

With the development of the chip technology and chip performance,ADC and DAC in the receiver of the communication system approached the antenna gradually. Therefore, analog front-end have decreased and been replaced by the digital front-end gradually, and communication system have been achieved the ideal SDR eventually.(1)The digital-to-analog of the input of digital front is researched and the key technology of the digital front including sampling theorem and multi-rate signal processing theory and modulation recognition technology of the posterior end in SDR is introduced.(2)The characteristics of the existing hardware platform,the basic structure and the work process of the platform was analyzed. The digital receiver hardware design was especially described.(3)The spectrum characteristics of the decimator in receiver-integral comb filter(CIC) and half belt filter(HB) was discussed.The factors that affected the performance of the filterwas was analyzed, the design requirements was put forward combined with its own characteristics and practical platform needs,and the CIC filter group and HB filter group were designed. Finally,simulation and demonstration in matlab and XILINX ISE9.1 were given. (4)A research and discussion, on the mondulation identification technology in back end of SDR,was done. The paper took the combination of the high-order cummulants and the fractal dimension as the characteristic parameters,and identified six signals by decision tree classifier using the characteristic parameters.Simulation shows that this method can identified more,and it has a good noise immunity and a high recongnition rate in certain SNR.In the end, a summary of the paper was made and the shortcome of the work and the direction of further research was pointed out in addition.Digital front-end technology was indispensable in the digital receiver which laid a foundation for the development of ideal SDR. Meanwhile,the identification technology of the modulation signal type in comunication as the important technology of software radio also has important research value and broad application prospect.