The DSP Algorithm And Software Design Of The Satellite Navigation Signal Simulator

The satellite navigation signal simulator can generate the navigation signal received by the user according to the motion status of the receiver and the signal transmission environment, provides a high precision signal source for the research and development of the receiver, and provides a test environment for the validation of the navigation and positioning algorithm. this thesis studies the algorithm design and its implementation in DSP of the satellite navigation signal simulator. The main work includes:1. Hardware scheme is designed according to the complexity of parameter calculation and the requirement of multichannel real-time performance. The formation of navigation message and the calculation of the signal parameters are completed by DSP, FPGA achieves the sub carrier and C/A code data generation and the signal modulation. The address protocol of DSP and FPGA data exchange is designed, and the communication between them is realized through external memory interface. The real-time updating of the signal data is realized by DSP response timing interrupt.2. DSP completed the conversion of the local time to GPS, satellite visibility judgment and navigation message generation; The spatial propagation error model is established, and the simulation of environmental parameters is realized; The signal propagation delay is calculated by the iterative algorithm, and the alignment of the navigation message and the C/A code is realized by using the signal transmission time; The method of linear approximation to the propagation delay is adopted, and the calculation formula of the control word with doppler frequency shift is derived, and the accurate control of the carrier frequency and the code frequency is realized.3. The satellite signal generated by the simulator is tested by the software and hardware receiver. The Doppler frequency shift and the code phase of the receiver are compared with the set value, and the error causes are analyzed. The positioning results are given to verify the effectiveness of the simulator.