Study On Group Delay Distortion Of TDRSS Reverse Link Channel

As a novel space-based tracking, telemetering and command system, Tracking and Data Relay Satellite System (TDRSS) represents a new direction in the international tracking, telemetering and command field. TDRSS plays an important role in increasing its coverage rate of the mediate/low orbit aircraft and decreasing the amount of ground telemetry stations in the satellite communication system. Therefore, it has a wide application prospect.In order to track and transpond multiple-targets, as well as reducing the complexity of relaying satellite, phased-array antenna based on beaming forming is applied in TDRSS, 30 helix antenna elements are used to receive spacecraft signal, each element signal will be transmitted to the Ground Terminal after being Frequency Division Multiplexing (FDM), and then the Ground Terminal make Digital Beaming Forming (DBF) on the basis of relative phase and amplitude difference of the 30 element signal. In order to eliminate adjacent channel interference, the 30-filter-group which are used to frequency-division demultiplexing are designed with sharp transition band. Because of the firlters'sharp transition band, group-delay will be exacerbated greatly, so the relative phase and amplitude difference of the each element are destroyed, which affect Direction-of-Arrival(DOA) estimation and DBF performance ,what is worse, it restricts the development and construction of the 2nd generation TDRSS.As far as the background,it is analyzed how group delay distortion affect DOA estimation and DBF performance by theoretical research and computer simulation in this paper.At the same time, Adaptive equalization was adopted to compensate group delay distortion.The main research contents and contributions are as follows:ⅠChannel characteristic of TDRSS reverse link was researched. Group delay distortion of TDRSS was analyzed, and the mechanism how inter-channel group delay mismatch of TDRSS comes was explored.ⅡThe mechanism how inter-channel group delay mismatch of TDRSS affect DOA estimation was explored, simulation model was set up in Matlab/simulink platform as well. And influence of DOA estimation due to inter-channel group delay mismatch of TDRSS was analyzed by computer simulation. ⅢThe mechanism how inter-channel group delay mismatch of TDRSS affect DBF performance was explored, simulation model was set up in Matlab/simulink platform as well. And influence of DBF performance due to inter-channel group delay mismatch of TDRSS was analyzed by computer simulation. Adaptive equalization was adopted to compensate group delay distortion which affects DBF performance of TDRSS.By analyzing the affection of DOA estimation and DBF performance due to inter-channel group delay mismatch of TDRSS's reverse link, significant conclusions have been drawn, which can lay the theoretical and technical basis for promoting the construction and development of TDRSS.