Research And Design Of Pseudo Satellite Network Localization System

In special environments,such as the valley of mine,tunnel and the city built-up "city Canyon",the satellite signals are blocked and unabled to provide accurate positioning services.The emergence of pseudo satellite enhanced positioning system provides a possibility for solving above problem.At present,foreign Locata pseudo satellite system has been put into military and commercial applications.The system overcomes a number of challenging technical problems,such as clock synchronization,near far effect,multipath effect,etc.It has been tested in various complex environments and the test results show that the positioning accuracy is better than other navigation and positioning systems.The technology of Beidou and Locata pseudo satellite system is referenced to research and design a pseudo satellite prototype system in this thesis,it can be used to be a platform for further research on the key technologies of pseudo satellite system.Firstly,the development of the domestic and international satellite system is studied,the composition and working principle of the Beidou pseudo satellite system is introduced.In addition,several key problems in the current pseudo satellite system are introduced in details,the navigation message of the pseudo satellite system is designed by referring to the frame structure of the second generation Beidou navigation message.Secondly,in view of the time synchronization problem in the pseudo satellite positioning system,a solution based on DDS is verified by referring to the TimeLoc technology in Locata.The digital signal processing technology in the pseudo satellite system is studied,including the generation of the baseband digital signal and the digital signal processing in the receiver.The acquisition and tracking algorithm of the pseudo satellite signal is realized based on FPGA.Thirdly,the effect of frequency offset on the tracking loop and signal demodulation is studied.The simulation results show that the proposed scheme can effectively solve the problem when the frequency offset is existed.Finally,a design scheme based on FPGA+Nios Ⅱ soft core for subsequent navigation message extraction and location solution is presented in this thesis,which provides a platform for the subsequent algorithm implementation.Then,the architecture of RF front-end in transceiver and receiver is given and designed.In this thesis,an integrated integration scheme based on Max2769B is presented and the driver of Max2769B is desingned which is based on NiosII soft core.The experimental results show that the proposed scheme can be used as the positioning receiver.Finally,the research work of this thesis is summarized and the direction and suggestions for further research are presented.