Research On Capture And Compensation Of Doppler Shift In TDRSS

The main tasks in this thesis focus on the capture and compesation of doppler shift in TDRSS, which is a part of digital receiver in TDRSS. It needs to research and develop the methods of capture and compesation.As a novel space-based tracking telemetering and command system, the Tracking and Data Relay Satellite System (TDRSS) represents a new direction in the international tracking telemetering and command field. Comparatively large doppler shift caused by high dynamic situation will do badly harm to communication capability, maximal doppler shift may be±100kHZ, so it is inacceptable for TDRSS. Due to spread spectrum communication used by TDRSS, Doppler shift has great influence to PN code, even PN code can't be demodulated correctly. So we should compensate it before demodulation. The thesis adoptes the methods with DMF and AFC loop to estimate and compensate doppler shift, which can not only achieve the desire of precision, but also can reduce capture time.The thesis firstly introduces the form and development of TDRSS, summarizes the signal format in forward and backward link. Then the conception of doppler shift .and influence to demodulation are offered. Traditional methods and characteristic of carrier recovery are following. At last the thesis offers the method and implement project by FPGA.