Research And Implementation Of Signal Simulation Algorithm For Multi-frequency Multi-constellation And Multi-function

Satellite signal simulator is used to develop and test signal receiver.With the continuous development of GPS,BeiDou system and GLONASS system,the application of satellite signal receiver is more and more wide.In order to meet the need of developing and testing of high-performance signal receiver for different constellations and different frequency,research of signal simulation algorithm for multi-frequency multi-constellation and multi-function is required,to ensure that the receiver can precisely position in high-speed movement.Based on the review of the research status of satellite signal simulation algorithms at home and abroad,the system components and positioning principle of GPS,Beidou system and GLONASS system is analyzed,and multi-frequency and multi-constellation multi-functional satellite signal simulators is studied and implemented.The work done are as follows:1.According to the mathematical model of satellite signals,the error model in the satellite signal simulation system is elaborated.The traditional satellite signal simulation algorithm process is improved,and the realization scheme of satellite signal collector-and-repeater and high dynamic satellite signal simulation system is designed.A method of extracting satellite ephemeris information from the navigation message is given,directly using the navigation message of the real signal without increasing the computational complexity,which makes the simulated signal more reliable.2.In order to simulate the Doppler effect of the receiver in high dynamic operation state,according to the principle of the direct frequency synthesizer,the pseudo code generator and the carrier generator whose frequency can be controlled are designed.With C language and Verilog language,using DSP to generate navigation messages,and using FPGA to generate pseudo-code and carrier,the signal collector-and-repeater and high-dynamic satellite signal simulation system is realized.The performance of system’s collector-and-repeater and high-dynamic satellite signal simulation is tested in this thesis.The testing results show that the signal collector-and-repeater can collect and reproduce the four-channel satellite signals in real time.The signal simulated by improved algorithm has higher positioning accuracy than the signal simulated by the traditional algorithm.