Method Study And Test Of C-band Common-view Time Transfer System With Transfer Mode

China Area Positioning System(CAPS)is the only Chinese satellite navigation comprehensive testing system,which has undertaken multiple experimental tasks of BeiDou satellite navigation system(BDS).CAPS have significantly contributed to the development of Chinese satellite navigation course.The main features of forwarding system compared to the straight system is payload placed on the ground,has the characteristics of flexible satellite change,frequency change,code change,in navigation war with strong survivability,may serve as an effective means to solve the needs of navigation and positioning applications in complex electromagnetic environment.Common-view time transfer system with transfer mode(TCV)is proposed based on CAPS,which is the development and application innovation of its navigation and positioning.This paper is mainly based on TCV thinking,studied the key technology and breakthrough,design and test verify the function and performance of TCV,which lays the foundation for the construction and application of the subsequent forwarding common TCV system.The current work includes:(1)The data fusion ionosphere correction method was proposed.Ionosphere dual-frequency correction method of Beidou GEO satellite was deloyed to correct the ionosphere delay of C-band TCV main station.The rental GEO communication satellite can’t provide real-time the function of C-band dual-frequency emission.To solve this issue,the ionosphere TEC value was calculated for the nearest BDS GEO satellites to the CAPS GEO satellite.The TEC value of CAPS GEO satellite links was then obtained by fitting the TEC value of the previously mentioned two satellites to CAPS GEO satellite links using linear interpolation.The correction amount of C-band CAPS GEO satellite can further be estimated.The efficiency of ionosphere dual-frequency correction method can theoretically reach 99%.Our current work also yields efficiency above 90% using data fusion.Both cases are above the efficiency 80% given by IGS ionosphere network products.Finally,the above experiments of TCV proved that the correction accuracy can be improved by the method proposed in the current work.(2)The performance of TCV testing platform was estimated using tri-station closure sums.TCV testing platform needs to be tested before using.Not only TCV experiments but also C-band TWSTFT experiments can be performed on the TCV testing platform.In the current work,the results of TWSTFT experiments were the reference for the TCV testing platform.In addition,the performance of C-band TWSTFT was verified using tri-station closure sums.Three groups of satellites with each group containing two satellites were tested using TWSTFT.The TWSTFT results of the first two groups were used to derive the results of the third group.The deviation between the derivation results of the third group and the as-obtained experimental results of the third group reflected the TWSTFT.The tri-station closure sums RMS data obtained from three ground stations: Xi’an,Kashgar and Sanya were all better than 0.5 ns,which reached the expected performance of TWSTFT.The designed performance of the TCV testing platform was also realized and further research of TCV can be conducted.(3)The TCV experiments were performed.The 3.7 m parabolic antenna with strong anti-multipath effects raised the accuracy of the TCV,which led to the conclusion that the TCV testing platform can be applied to verify the performance of TCV.After the analyzing the error source and the correction method for the TCV,long-term TCV and TWSTFT experiments were conducted among ground stations in Xi’an,Kashgar and Sanya.Clock differences were calculated by means of two methods,mutual differences were further obtained.The resulted mutual-different STD value between Xi’an and Kashgar and the mutual-different STD value of between Xi’an and Sanya were both lower than 1 ns.In this work,the operation method and the main error source of the TCV were investigated.The results proved that the STD value of the mutual difference between the TCV and the TWSTFT reached 1 ns,which was a better performance than the conventional GNSS,and a slightly worse performance than the TWSTFT.In terms of stationary users,the TCV was more promising,because the instruments of the TCV was much more cost-effective compared to the TWSTFT.