Research On Spaceborne High Precision Ranging And Time Synchronization

The background of this thesis is a low-frequency interferometric satellite formation project flying around the lunar.Communication,Ranging & Synchronization(CRS)is a prerequisite for interferometric measurements of satellite formation,and is considered one of the key technologies in the field of payload coordination.According to the research work of this paper,there are many inter-satellite links to achieve the communication function,and there are many projects to achieve a very high precision(200km distance to 1 ~ 2mm accuracy)inter-satellite range,high precision time Synchronization(better than 1ns,now in the research phase).However,the realization of these functions,are still only a single function,not in a single RF link,while completing the whole CRS functions.In backgrond project,the size,weight,power consumption of the satellite have strict restrictions,meanwhile,CRS equipment is also subject to aircraft orbit,power and other restrictions,without GNSS timing,temperature control technology to imporve the measurement and post-processing accuracy.This paper focuses on the inter-satellite scheme of CRS integration which satisfies the above constraints.The CRS system of this project needs to reach the target for: within 1 to 10 km distance,while completing 1Mbps signal source rate for transmission,1m on ranging accuracy and 3.3ns for time synchronization accuracy.In this paper,we first study the signal system of integrated CRS technology: GMSK + PN(Gaussian Filtered Minimum Shift Keying + Pseudo Noise)modulation which can combine both communication and ranging.In this paper,I have studied the modulation parameters,the demodulation scheme,the ranging signal separation and the Pseudo Noise ranging signal capture and tracking.In this paper,the integrated CRS technology is proposed to provide a two-step strategy for measuring and time discipline in the process of providing synchronous and low-jitter reference clock sources.The accuracy of measurement is a prerequisite to meet the requirements of mission accuracy.This paper clarifies the principle of dual one-way range measurement(DOWR),modeling and analying the various error sources.Error elimination technology is analyzed and compared.The performance limitation of this technology has been studied in the existing conditions.The measure information of the distance and time difference,needs to be filtered by post-processing algorithm,and then output the final distance information through the Kalman algorithm,output high precision,low jitter reference clock signal by PI algorithm.In this paper,the post-processing algorithm have benn studied in-depth.