Research Of Satellite Signal Synchronization Technology For High Dynamic And Low SNR

With the rapid development of the Global Navigation Satellite System, it plays a more and more important role in people’s life, and has been used more and more widely.The first step of navigation and positioning is to realize the synchronization of navigation satellite signal.To realize the synchronization of signals,it has to achieve the acquisition of navigation signals.Due to the particularity of the navigation satellite channel,the received signal will be affected by high noise and large Doppler frequency offset.The normal navigation signal acquisition algorithm can not adapt to the low SNR and high dynamic environment.Therefore, it is a very important problem to study how to acquire the navigation signal in low SNR and high dynamic environment.This thesis investigates this problem. Firstly the problem of long coherent integration being limited by the affecting of navigation signal bit sign transition is studied. On the problem of extending the the coherent integration time, aiming at the deficiency of the traditional half-bit method and full-bit method, the thesis proposes the improved half-bit method and this method can avoid the impact of bit transition and extend the integration time. The proposed progressive all-bit method is a compromise between the halfbit method and the all-bit method, which can reduce the computation complexity while keeping the detection performance. Afterwards,based on the insufficient of Time Parallel Acquisition Algorithm with Transition Detection(TPATD) algorithm can only extend the integration time to 20 ms, this thesis puts forward the improved TPATD algorithm, which can make the coherent integration not affected by bit transition, and extend the coherent integration time to 40 ms. The improved algorithm can improve the detection performance of 3dB. Last, aiming at the problem of large Doppler frequency offset in high dynamic environment, a parallel frequency algorithm based on block average preprocessing is proposed, which combines the block averaging method and the Partial Matched Filter and Fast Fourier Transform(PMF-FFT) algorithm. The algorithm extends the search range of frequency, and can realize the frequency parallel search and achieve the fast acquisition of signal in high dynamic environment.Simulation results show that the algorithm can effectively reduce the computational complexity, and has a better performance than the traditional parallel frequency acquisition algorithm.