Design And Implementation Of Multi-GNSS Signal Recording And Playback System

GNSS signals are usually subject to human and natural interference,such as radio frequency interference,ionospheric scintillation and multipath effect.In the development and research process of GNSS receiver,although the simulator can generate all kinds of GNSS signals,some special environments cannot be simulated by GNSS simulator.Because of the non-repeatability of the GNSS signal,the researchers can replay the signal repeatedly in the laboratory to repeat and study the signal of the environment if the GNSS signals can be collected,stored and replayed in these special environments.In order to achieve the acquisition,storage and playback of GNSS signals,a design plan of software radio experiment platform based on USRP and GNU Radio is proposed in this thesis.In view of the requirements of the system design,the experiment scheme of the acquisition and replay system is designed,and the experimental platform is built,including the hardware experiment platform and the software experiment platform.At last,using this system to collect and replay the GNSS signals of analog signals and real environment respectively,the system is verified and tested,and the received data are analyzed and counted.The main research work of this thesis is summarized as follows:(1)the requirement of the project is to collect,store and replay the original signal of GNSS signal.Based on this,a design idea of using the idea of software radio is proposed.The software radio hardware platform USRP and software platform GNU Radio and GNSS SDR are determined.And an experimental platform for GNSS signal collection and playback is successfully built.(2)based on the analysis of the characteristics of the GNSS signal,the scheme of the acquisition and playback system is designed respectively.In the design of the experimental scheme,the Ublox commercial receiver is used to analyze and process the GNSS signal,and the result is the reference of the replay signal verification.Using open source project GNSS SDR to process data stored in computer,we get the signal tracking result file and analyze the collected signal.The carrier noise ratio(C/N0)is a very important parameter when the performance evaluation of commercial receiver Ublox and this system is carried out.The simulation analysis of three common noise ratio estimation algorithms is carried out in this thesis,and the performance of the three algorithms is compared.(3)complete the verification of the system.First,the GPS and GLONASS signals are generated by the analog signal generator.The system is used to collect and store it and replay it to the Ublox receiver.The receiver realizes the positioning of the replay signal,and the result of the positioning is consistent with the location of the analog signal.For the satellite signals in the real environment,this system has realized the acquisition and replay of the signals of the three navigation satellite systems of GPS,GLONASS and Beidou,and verified the performance of the system through the spectrum analysis,the satellite capture results,the satellite star map and the ratio of each satellite signal to the ratio of the signal to noise ratio.