The DSP Software Development And Interface Design For GNSS Satellite Navigation Signal Simulator

According to the motion scene model set by the user,the satellite navigation simulator can precisely simulate the satellite navigation signals received by the receiver and can provide a highly reliable simulation environment for the development and testing of the navigation receiver.Based on the hardware scheme of satellite navigation simulator,this dissertation studies the design and implementation of DSP algorithm software in the IF signal simulation.The main works completed in this paper are as follows:1.A baseband signal generation scheme of the satellite navigation simulator based on "DSP + FPGA" hardware architecture is designed.The multi-core DSP receives scene files set by the user and calculates parameters required by satellite signal generation.The FPGA real-time generates satellite digital IF signals according to the transmitted parameters and transmits them to the D/A and the RF module for transmission.The data transmission scheme is designed between DSP and FPGA.The SRIO bus interconnection is adopted to realize the high-speed data transmission between hardwares.The real-time update of parameters required by the FPGA is realized through the response of DSP to the doorbell interrupt.The frame structure of transmission data is designed and the ping-pong operation mode in the FPGA is used to achieve high-speed data cache.2.The DSP algorithm of GPS,Beidou and GLONASS satellite IF signal source is designed and implemented.The satellite signal data of each system is processed and the user motion model is extracted from the scene file in the multi-core DSP;the navigation message data is stored and the ephemeris data of each system satellite is calculated;the visibility of satellites is determined and the time and coordinate conversion of each system satellite is completed;the propagation error model of signal is established and iterative computation is performed to achieve accurate calculation of propagation delay.the signal transmission time is set and the initial parameters of signal generation is calculated,the signal third-order doppler error model is established and the corresponding control word parameters is determined.3.The navigation signals generated by GPS,BeiDou and GLONASS analog sources are tested and analyzed by software and hardware receiver.The error of parameters between the initial set value and the measured value of the user is compared and analyzed,which verified the validity and reliability of the simulator design scheme.