Design and implementation of a novel multi-constellation FPGA-based dual frequency GNSS receiver for space applications

摘要

In the recent years, the use of GNSS receivers for onboardsatellite orbit determination has become a commonsolution, as it considerably simplifies the overallarchitecture if compared to traditional orbit determinationsystem such as radiometric tracking. Different challengeshave to be faced while designing a GNSS system for thistype of application, since in general the terrestrial receiverare not designed to guarantee their performances if placedin and orbital environment. The differences can begrouped in two main areas: the first is related to the signalproperties, as higher signal strength variations, higherDoppler and Doppler rate must be accounted for, todesign the proper acquisition and tracking strategy. Thesecond group of differences is related to the spaceenvironment that affects the electronic systems in generaltrough severe temperature variation and the various typesof radiations. These aspects are combined together in thedesign of a novel FPGA based GPS and Galileo receiverfor space applications. This paper describes first thereceiver requirements, that were defined troughsimulations, using a GNSS full system and navigationsoftware simulator, which provides also PVT accuracyestimation by the implementation of the navigation filter.The receiver hardware is based on the Xilinx FPGA,which incorporates a PowerPC in form of hard processor.The paper describes also the electronic hardware, togetherwith the tracking algorithms, providing details about thecombined third order PLL carrier aided DLLimplementation. On-board navigation algorithms are alsodiscussed with respect to the relevant error sources,showing that the achievable positioning accuracyprovided by the simulator ranges from sub-meter for thedual frequency solution to one-three meters for the singlefrequency solution.