The Research Of Carrier Synchronization And Signal Demodulation In New Generation Space TT&C System

Space TT&C system is an essential part of space technology. It plays an important role in science research and national economy development. With the rapid progress of space technology, old space TT&C system take on much shortage and new generation space TT&C technology is developing towards digital way. Digitalizing includes modulation mode digitalized and equipment all digitalized. Aiming at this characteristic, this thesis research in carrier synchronization and signal demodulation of new generation space TT&C system.Down link channel of new generation space TT&C system generally select QPSK as its modulation mode. Firstly, carrier synchronization of QPSK is studied in the thesis, and then the key question-carrier synchronization in low SNR and severe Doppler frequency shift is systemic analyzed. In addition, different existing project are analyzed and compared. Based on this, the thesis brings forward the design project of carrier acquisition in severe Doppler shift. Automatically scan, decision feedback loop and Costas loop combined together are adopted. Simulation proved the performance accord with system need. Further more, a synchronization project using error function linearization as the core is brought forward. It used to improve carrier synchronization performance in low SNR. Following this, the thesis research digital demodulation of QPSK and analyze the digitalizing means of key module. Digitalizing demodulation arithmetic is given. The thesis also researched in phase ambiguity of coherent demodulation, and then brings forward a new method for settling phase ambiguity. Furthermore, in order to supplement multi-object TT&C capability of new generation space TT&C system, GMSK modulation is recommended by CCSDS because of its preferable frequency speciality and miscode performance. The thesis analyzed characteristic and demodulation realized of GMSK signal. Attempting to design a universal multi-mode demodulator of BPSK, QPSK and GMSK, the thesis studied modulation identification technology. The identification means of three kinds of modulation types based on theory decision-making is analyzed. Finally, identification means of modulation types based on ANN is advanced.The thesis based on theory analysis has done corresponding simulating. It proves the feasibility and validity of arithmetic.