Research Of Demodulation Technique For Leo Satellite Tdma/oqpsk Signal

This paper is devoted to research on demodulation technology in TDMA/OQPSK burst signal of low orbit satellite, including signal dopple frequency offset, signal detection, symbol timing estimation, and carrier frequency offset estimation, which is one sub-project of a key project in advance of author's work unit.This paper analyzes the features of signal to be demodulated, and presents an overview of theoretical basis of demodulation technology in burst signal, including signal detection, carrier frequency synchronization, and symbol synchronization. According to the features of signal and non-cooperation receiving, priority-to-the-easy strategy is determined, that is to complete the demodulation of single burst signal to clarify signal frame's unique word, with which continuous demodulation can be followed on the basis of burst detection.As to demodulation of single burst signal, decision-feedback loop and linear interpolation filter are used respectively to track carrier and adjust location reference to current demodulation theory, which provides quantitative analysis to dopple frequency offset of signal, maximum theoretical value of dopple frequency offset of plane signal in different orbit, and the basis for designing and selecting of loop filter.This paper analyzes common used bi-sliding-windows signal detection technology and makes simulation comparison to actual used technology of"unique word correlation + FFT detection", with which forward estimation to carrier frequency offset and symbol timing is carried through.