Assessment And Verification Of Code-Carrier Coherence On BDS

Pseudorange and carrier phase are two basic observations generated by Global Navigation Satellite System(GNSS)receiver for each satellite.Because of the effects of ionosphere delay,multipath,or the unsatisfactory performance of satellite emission source,the ranging code and carrier of navigation signal have different transmission characteristics resulting in non-coherence of the distance code and the carrier.That is the increment of the code pseudorange of adjacent two epochs is not equal to the increment of the carrier pseudorange of the same adjacent two epochs at the same frequency for the same satellite.The evaluation of code-carrier coherence is critical to monitor the satellite signal quality and then to meet the navigation positioning accuracy and reliability requirements.Aiming at the problem,evaluation and verification process of code-carrier coherence on Beidou Satellite Navigation System are carried out in this paper.The main contents are as follows:(1)The overall scheme of evaluation of code-carrier coherence is designed firstly and operational ideas of Code-Carrier Divergence are specially analyzed.Based on the composition of CCD model,the mathematical descriptions about the monitoring value and detection threshold of CCD are provided.The experimentally detection results are given by using the original observation data of the Beidou Satellite Navigation System received by the multi-system multi-frequency receiver on point positioning.(2)Based on the method of multi-frequency combination observation,the original observation data of Beidou Satellite Navigation System are processed,which the ambiguity is determined and the cycles are also detected and repaired successfully.The effectiveness of multi-frequency combination observation method and the correctness of theoretical analysis are verified experimentally.(3)The hardware delay deviations of the satellite and receiver are estimated by using the Kalman filter method.Also,the hardware delay deviation results of each satellite are given experimentally.(4)According to different states of the ionosphere,two different methods are selected to evaluate the code-carrier coherence on Beidou Satellite Navigation System.It is verified that the deviation of the code-carrier coherence at different frequencies for each Beidou system satellite meets the requirements of the International Civil Aviation Organization.