Research On The Fast Acquisition Algorithm Of High Dynamic GNSS Signal

In recent years, with the rapid development of global navigation satellite system(GNSS), the demand for navigation service has been rising fast. The client has moreand more high demand for the precision of navigation. The speed of acquisitionprocess under high dynamic accuracy is a crucial problem of ensuring the receiver’shigh accuracy. The acquisition process of navigation signal is essentially atwo-dimensional search of the PN code phase and carrier wave Doppler frequencyshift. Under high dynamic situation, the Doppler frequency shift of the received signalis so large that it’s not conducive to rapid acquisition. In this paper, we study theacquisition algorithm based on PMF-FFT in order to solve the problem of acquisitionunder high dynamic situation of high Doppler frequency shift.Firstly, this paper analyzed the composition, signal structure and features, thepositioning principle, the basic structure of the receiver of GNSS system, and theinfluence of GNSS signals under high dynamic situations. In this part, we mainlyfocused on the analysis of the generation and the related features of GPS C/A code.Secondly, this paper analyzes the basic principle of the acquisition of GNSSsignal. it has analyzed and compared two traditional acquisition methods, thetime-domain siding correlation algorithm and the acquisition algorithm base on FFT.Then it mainly studied the matched filtering algorithm, having a detail derivation ofthe acquisition theory and analyzed the performance of the acquisition algorithm.Then it points out the defects of large Doppler frequency shift. the PMF-FFTalgorithm based on the matched filtering algorithm uses FFT method to compensatethe attenuation if the matched filter in large Doppler frequency shift. Mathematicalmodel the basic principle of the algorithm is given in this paper, and its amplitudefrequency response characteristics is derived and analyzed.For the problem of the selection of partial matched filter length of PMF-FFTsystem, this paper gives the impact of changing the length to some performanceindicators, and then gives the guiding ideology of selection of the filter length. Then itdiscussed the defects of scalloping loss of PMF-FFT and mainly adopted two ways,zero padding and windowing for improvement. Zero padding can increase theresolution of FFT processor without increasing the bandwidth. And this paper studiedand compared the various ascending cosine window, then improve them. Furthermore, it proved the superiority of the algorithm by analyzing its acquisition performance.