Design Of Beidou Pseudo Satellite Transiver Based On USRP

Pseudolite(PL)is a navigation signal generator that is deployed on land or sea reefs,which can be used to solve the problems that GNSS has low positioning accuracy or unaccessed in some environments.What's more,a synchronous pseudolite network composed of multiple pseudolites can be used to provide navigation and positioning independently.With the initial completion of the Beidou Global Navigation Satellite System(BDS),Beidou satellite navigation technology has entered a new stage of research and development,and the pseudolite technology which is used in BDS has become a research hotspot of many scholars and research institutions.Based on the research of BDS and traditional pseudolite technology,a prototype system of Beidou pseudolite transceiver is designed based on USRP,and some technical verifications on key technologies involved in Beidou pseudolite are carried out.Firstly,the domestic and international research status of Beidou pseudolite key technology and software radio technology are reviewed,the structural characteristics of the Beidou pseudolite signal are studied with reference to the signal structure of BDS.Besides,the time synchronization processing scheme of Beidou pseudolite is studied through comparing and analyzing multiple pseudolite time synchronization techniques.Secondly,the composition of Beidou pseudolite system is introduced in detail,the overall design block diagram of pseudolite transceiver based on USRP is given and the GNU Radio and USRP developing platforms are built.The generation mechanism of Beidou pseudolite signal is studied in detail and the implementation of the Beidou pseudolite baseband signal source is completed on the GNU Radio as well as some simulation verifications.Moreover,the hardware function designs of RF and digital-to-analog conversion module of the transmitting unit based on USRP are given.Thirdly,combined with the working principle of Beidou pseudolite transceiver,the IF digital signal processing mechanism of the receiving unit,including signal acquisition and tracking algorithm,is studied.And the IF digital signal processing function of the transceiver and related simulation are implemented on the GNU Radio software platform.The functional design of the receiving unit is completed based on USRP,including RF processing on the daughter board and analog-to-digital conversion on the motherboard.Then,as to the problem of time synchronization technology between the multiple Beidou pseudolites,the synchronous networking scheme of the Beidou pseudolite system and the time synchronization mechanism between the Beidou pseudolite transceivers are given based on the analysis of the time synchronization technology of the Locata system.The relevant algorithm is designed,and the simulation result verified that this scheme can effectively achieve accurate clock synchronization between Beidou pseudolite signals.Finally,the research works of this paper are summarized and forecasted,and the directions and suggestions for the next research are put forward.