Research On Multi Mode GNSS Receiver With Receiver Autonomous Integrity Monitoring

The multimode GNSS receiver is a receiver that performs positioning by receiving signals of more than one satellite system,such as positioning the user coordinates by using the GPS L1 C / A signal and the BDS B1 signal.With the increasing number and availability of global navigation and positioning satellite systems serving in space orbit,the use of multimode GNSS receivers will become increasingly widespread.At the same time,the reliability of the positioning results of the receiver is required to be higher and higher,therefore,the receiver autonomous integrity monitoring(RAIM)technology is proposed to improve the reliability of positioning results.RAIM is a technology that detects faults and identifies faults by using redundant information of satellite signal.The core idea is to perform a consistency check on the positioning results using satellite redundant information,thereby enhancing the credibility of positioning results.Therefore,the author designs a multi-mode GNSS receiver platform based on GPS / BDS siganls,and designs the RAIM algorithm for this platform to eliminate the fault and improve the reliability of the satellite positioning results.First,the author designs a multi-mode GNSS receiver.Based on the principle of single system positioning,the principle of multi-system positioning is deduced.Based on the multi-system positioning equation,the signal processing processes before positioning,including acquisition,tracking,synchronization and navigation message parsing,are studied.The similarities and differences between the single system and the multisystem are analyzed,and the multi-mode receiver besed on GPS / BDS signal is designed,and some structure improvements is proposed to optimize the design.Secondly,based on the multi-system positioning model,the author uses the parity vector method to monitor the receiver autonomous integrity and thus improve the positioning reliability.The RAIM technique is based on the consistency detection technique of positioning residuals.Therefore,the processing flow of the multi-system positioning method is improved by the introduction of the RAIM algorithm which can detect and identify the fault and remove the fault data,so as to position the user coordinates once again.The RAIM algorithm is designed using the parity vector method.Single fault model and multiple fault model are studied,and the statistics and thresholds are designed to check and identify single fault or multiple faults,so as to monitor the integrity of satellite signals and improve the reliability of positioning.Based on the FPGA,the multimode satellite signal acquisition and tracking is realized.Based on the host computer,the synchronization,teletext analysis and positioning solution and integrity detection are realized.The output data in the hardware processing proves the design of multi-system satellite signal processing to be effective;In the software part,the normal positioning result is output firstly,and then single satellite fault model and multi-satellite fault model is simulated.Through the RAIM algorithm to deal with the model,the algorithm is effective for single fault but needs further improvement in multi-fault processing.