Research On GNSS Triple Frequency Algorithm Based On Software Receiver

Since the beginning of the development of GPS in the 1970 s,the global positioning system represented by GPS has developed very powerful functions.Provide 24-hour and global coverage of service has been deeply into the modern industrial production and life,in the pedestrian navigation,car navigation,surveying and mapping,played a key role in precision agriculture and other areas.The modern satellite system is equipped with multiple frequency bands and has done a lot of research on the joint positioning of multiple systems.However,in some places that cannot be reached by satellite signals,such as indoor,tunnel,underground garage,etc.,how to ensure the provision of traditional and effective navigation and positioning services has become a new hot issue.The work of this paper is mainly divided into three aspects:1)This paper attempts to improve the success rate and accuracy of system initialization by using multi-frequency combination based on the difficulty of system initialization exposed in past tests.Based on threefrequency combination,the application and improvement of traditional TCAR algorithm in ground navigation system are explored.The fixed ground-based pseudolite station leads to the poor geometric diversity,which may not provide the redundancy required when using Least-squares Ambiguity Decorrelation Adjustment(LAMBDA)algorithm to solve the ambiguity.In contrast,in the surface environment,the ionospheric errors in atmospheric errors can be ignored,and the difference of observations can be made through the bidirectional time synchronization principle,which is a great advantage for the use of TCAR algorithm.The experimental results show that the ambiguity can be determined after the combination of the three frequencies by using cascading ambiguity resolution,which can reduce the computation amount,reduce the operation time and improve the efficiency.2)Based on the present situation of the foundation pseudolite,combined with domestic and foreign research carried out on the foundation of pseudolite system architecture research.As a derivative of the traditional satellite navigation system,the ground-based pseudolite sets up the "satellite" on the ground,that is,the ground base station transmits the navigation signal to realize the traditional positioning service.The experimental data of this paper were collected from the test experiments carried out in the research process of the industry-university-research project.The experiment was carried out in the port,and the dynamic positioning,static positioning and anti-interference performance of the ground-based pseudolite were tested in the field by setting up the navigation system.The hardware composition of the system construction platform is given in this part,and a transceiver based on software radio architecture is built.3)After the algorithm principle is verified by MATLAB simulation,download the algorithm program to the software receiving machine platform for field test and verification.After the initial value is calculated and input into the system,the moving trajectory of the receiver is described and the dynamic positioning performance is demonstrated by the error analysis of the positioning results of the receiver at each point.It is verified that the tri-frequency resolution fuzziness can give a high precision positioning value,and then the positioning system can be initialized to achieve high precision positioning.The long-wavelength characteristic of three-frequency combination can improve the ambiguity resolution speed and success rate,so as to achieve the ambiguity resolution and improve the positioning accuracy under multi-path interference.Experimental results show that the improved TCAR tri-frequency combination positioning algorithm can achieve the positioning accuracy of cm level.