Research On Key Techniques Of High Sensitivity GNSS Software Receiver

The global satellite navigation system can provide real-time all-weather high-precision three-dimensional position,speed and precise time information,and it has become an important tool in national defense and civilian life.Nowadays,with the rapid development of information,the complex baseband signal processing algorithms and the hardware circuit design of the satellite navigation system receiver seriously restrain the intelligent application process of the satellite navigation system.The high sensitivity acquisition algorithm of Beidou II navigation system receiver is investigated in this thesis,and provides technical support to the extensive application of the Beidou satellite navigation system.By adopting optimization algorithm in the baseband signal processing,the problem of signal acquisition in the baseband signal processing of satellite navigation receiver is solved without relying on any additional hardware acceleration components.The main work of this thesis can be summarized as follows:1.The structure and development platform of Beidou ? software receiverFirst,combined on the existing research results of the laboratory,a Beidou? software receiver development platform based on C language is built,and whose main function is to realize signal capturing.Beidou ? satellite signal with noise is generated through this development platform.By constantly adjusting the signal-to-noise ratio of the signal,the received data under different signal-to-noise ratio is simulated.Also,the effects of Doppler shift is simulated through the modification of the carrier frequency(IF:Intermediate Frequency).Finally,by adjusting phase of the PRN code,the propagation delay is simulated.The above work lays the foundation for further verifying the high sensitivity capture algorithm.2.The research and simulation of high sensitivity algorithmThe high-sensitive acquisition algorithm is investigated based on the receiver platform established.Traditional algorithms for improving the capture sensitivity include coherence accumulations and noncoherent accumulations.The simulation platform established is used to simulate and generate the source,simulate the weak satellite signal to realize and verify the high-sensitive non-coherent cumulative acquisition algorithm.3.A fast processing algorithm presented for NH code of Beidou receiver under weak signalThe secondary code(Neumann-Huffman,NH code)of Beidou ? satellite signal needs to be modulated.NH code symbols are likely to jump in every millisecond,what's worse,it is true that the extending cumulative time cannot bring improvement in capture sensitivity of the receiver.To solve this problem,this thesis presents a traversal algorithm,by searching all the combinations of NH codes in the cumulative time,trying to find a code sequence that is completely aligned with the NH code in the received signal.And the impact of symbol transition of NH symbol can be eliminated by multiplying the NH code and received signal.Simulation results show that comparing with the traditional acquisition algorithm,the presented algorithm can make the receiver obtain a gain of at least 2dB.