Analysis And Compensation Of Non-uniform Frequency Shift In Reverse Link Of TDRSS

Tracking and Data Relay Satellite System(TDRSS)is a system that uses geosynchronous satellites and ground terminal stations to carry out orbit measurement and control,data relay and continuous tracking for high and low orbit spacecrafts.It has very high strategic value and has become the focus of development.Therefore,the study of TDRSS is of great significance.Based on the TDRSS technology of DBF,the 30 channel array signals on the relay satellite are transmitted to the ground terminal station through the frequency division multiplexing through the frequency division multiplexing.Due to the relative motion between the earth and the ground,the use of high frequency carrier and multiple frequency conversion,there will be non uniform frequency offset in the 30 channel,which will seriously affect the performance of the DBF under the satellite.In view of this problem,this paper,based on the National Natural Science Foundation Project "Research on the performance degradation mechanism and upgrading technology of DBF under TDRSS reverse link",verified the existence of non uniform frequency offset between TDRSS reverse link channels through mathematical modeling and computer simulation,and analyzed the influence of inter channel non uniform frequency offset on DOA and DBF performance.The compensation method of frequency offset.The main contents of this paper are:(1)Using the orbit parameters in the satellite ephemeris and the geographic location of the ground terminal stations,the Doppler frequency shift mathematical model of the TDRSS reverse link channel is established by using the geometric vector method.The influence of other factors such as instability of frequency source in the frequency conversion process,the gravitational pull of the sun and the moon,and the orbital drift of relay satellites on the non uniform frequency offset are analyzed in depth.(2)The TDRSS reverse link structure using the satellite DBF system is studied.The influence of non uniform frequency offset on DOA estimation and DBF performance is analyzed by mathematical modeling and computer simulation.Theoretical and simulation results show that the non uniform frequency offset between channels can seriously affect DOA estimation and DBF performance,deteriorate system performance and present time cumulative effect.(3)The compensation measures for non uniform frequency offset are studied.An adaptive frequency offset algorithm based on steepest descent algorithm is proposed to compensate non uniform frequency offset,and variable step size is improved for the fixed step length of the algorithm.The simulation platform shows that the improved adaptive frequency offset compensation algorithm has obvious advantages in reducing the pointing error and reducing the number of iterations.The accuracy of the DOA estimation and the DBF pointing performance of TDRSS are improved obviously after the algorithm is compensated...