Synchronization Algorithm For High-order BOC Modulated Signal & Performance Optimization

With the development of satellite navigation technology, several new signals adopt BOC modulation in order to achieve the goal of spectrum separation and compatibility among GNSS. However, high-order BOC signals bring difficulties in signal processing because of its wide spectrum and large number of side-peaks with its auto-correlation function. Concentrated on this, the study of this paper contains the following aspects:First, this paper gives an overview of the signal structures of different satellite navigation systems, summarizes the research states of the acqusition and tracking technology for high-order BOC signals, makes a comparision among several navigation signals and points out that there are better properties for high-order BOC signals in code tracking accurancy and anti-jamming.Second, in order to improves the acqusition speed and achieves a more accurate result of the time-delay of the input high-order BOC signal, this paper proposes a fast acqusition method which consists of two steps: BPSK-like coarse acqusition and parallel match fine acqusition. In terms of serial search acquisition, this paper makes a parameter optimization which based on the assumption of a biggest bias between the local signal and the received signal while the mean acquisition time to be the minimum, and gets the results that for BPSK-like coarse acqusition, the optimal search step is a half code chip, and testifies that multiple dwell serial search can have a significant reduction on the mean acqisition time. Meanwhile, this paper makes an analysis on the central peak acquisition probability of parallel match fine acqusition, gets the conclusition that the extension of the coherent integration time and the addition of the non-coherent number can reach a higher central peak acquisition probablity, and the simulation proves that the central peak acqisition probablity could have a promotion for about 0.3dB by make a linear combination of the adjiacent detection results.Third, as for the problem that the combined time-delay estimation is unstable when using Double Estimator method tracking high-order BOC signal, this paper shows that the affect factors are the carrier-noise ratio,the dynamics of signals,the interference and the multipath. Analysis and simulation proves that the reduction of the delay between early and late of DLL and loop noise bandwidth can reduce the leap probablity which related to thermal noise, the reduction of the delay between early and late of DLL and a proper choice of loop noise bandwidth can reduce the leap probablity which related to thermal noise as well as dynamic stress.