Research On Key Technology Of FY-2 IF All-Digital Demodulator

Firstly, this paper indicates the background and source of the project, and briefly introduces the developing situation of the digital down conversion and the timing synchronization. Then, based on the overall structure of the IF all-digital demodulator for FY-2 meteorological satellite, the digital down conversion and the timing synchronization are deeply researched. Through the analysis of the digital down conversion principle, the selection of the sample rate is discussed on emphasis, and the proper sample rate for the project is determined in which many various factors are considered. Then according to the request of down-speed signals processing, the extraction scheme and the detailed half band filter design are provided. In the timing synchronization, the principles and functions of every part in the overall module design are introduced and analyzed. In the loop filter design, the steps of getting loop filter parameters at the Simulink platform are researched, and a method of switching loop bandwidth combined with the karam lock algorithm is provided. In the end, the simulation of QPSK demodulation system and the implementation of the digital down conversion and the timing synchronization in FPGA are given.