Baseband Signal Processing Circuit Design For Ground-based Radio Navigation Terminals

The Global Navigation Satellite System(GNSS)is an important information infrastructure for human development as it can provide all-weather uninterrupted navigation and positioning and timing services to a wide range of users on the Earth’s surface and in near-Earth space in real time.However,since the number of visible satellites in GNSS does not reach the required number for positioning in use scenarios such as valleys,deep forests and underground,it is difficult to meet the demand for highprecision positioning in these complex environmental conditions.For this reason,groundbased radio navigation as a useful complement to GNSS has been proposed and widely studied by researchers.To address this situation,this thesis designs and implements an algorithm for baseband signal capture and tracking based on ground-based radio navigation and completes board-level testing and algorithm verification in ZYNQ platform.The main work and research contents are as follows:1.In response to the shortcomings of traditional GNSS,this thesis investigates the development status of ground-based radio navigation system,systematically researches the basic theory of ground-based radio navigation and positioning principle,analyzes its system architecture composition and signal structure,clarifies the research significance of baseband signal capture and tracking algorithm,derives the mathematical model of related algorithms and analyzes the performance and applicability range of different algorithms.2.The ARM+FPGA architecture is established for the implementation of baseband signal processing functions,and the whole is divided into two modules: capture and tracking,the classical capture algorithm is compared and the parallel code phase search algorithm with fast computation speed is selected for the capture scheme with cyclic interrupt control at the PS side,the linearity of different discriminators is analyzed and compared,and the Costas phase-locked loop with inverse tangent discriminator and the delayed phase-locked loop with normalized overrun minus hysteresis power discriminator are selected as the scheme to achieve tracking.3.The top-down idea is used to design and implement the baseband signal capture and tracking circuit for ground-based radio navigation terminal in ZYNQ development environment.The capture includes carrier NCO,uniform downsampling,FFT/IFFT and peak search modules,and the tracking includes carrier NCO,pseudocode NCO,pseudocode generation,carrier loop discriminator,code loop discriminator and loop filter modules,etc.The capture and tracking is controlled by ARM programming on the PS side,and the function is simulated and verified using Vivado Simulator.4.Completed the board-level testing of the ground-based radio navigation terminal’s baseband signal processing and control circuit on ZYNQ.The results show that the capture module can complete the capture of a base station signal in 41.3ms,and the tracking module can complete the stable tracking of the carrier ring and pseudo-code ring and output the navigation data code and observation in 10 ms.