Research and Relization on Fast Acquisition Algorithm of High Dynamic DSSS Based on PMF-FFT
|School||Graduate School , Chinese Academy of Sciences ( National Time Service Center )|
|Course||Communication and Information System|
|Keywords||PMF FFT Windowing Zeros Adding Probability of Detection AverageAcquisition Time|
It is a critical issue on ensuring the receiver’s high accuracy and real time in high dynamicsituation.The acquisition process of the spread spectrum signal need get both the pseudocodephase and carrier frequency.It’s is a two-dimensional acquisition process. Capture difficulty isincreased because that high dynamic spectrum spread signals have large carrier Doppler. offsetchange rate. Besides, the Doppler resolution the acquisition process get has direct relation withthe tracking speed of tracking loop, even with the successful tracking. Thus, this paper focus onthe successful acqusition and high Doppler resolution with large carrier Doppler.The acquisition algorithm based on PMF-FFT architecture used in this paper can get the carrierdoppler as well as pseudo-code phase simultaneously. This method converts two-dimensionalacquisition process to one_dementional. Acquisition time is greatly reduced.Windowing andzeros-adding is used to improve acquisition performance.This paper firstly introduced the acquisition algorithm based on PMF-FFT architecture,analyzed two ways, zero-padding and windowing, used to reduce Scallops Loss, reformedwindow construction and simulated improved acquisition algorithm, and then comparedacquisition performance of improved algorithm with before algorithm. In addition, this paperanalyzed variable step search method as well as the influence of PMF parameters on captureperformance. Moreover, it used adaptive threshold technology to improve the acquisitionperformance. Finally, based on the theoretical analysis of algorithm, FPGA implementation ofthe GNSS receiver acquisition algorithm was researched. The design method of receivermodule is detailed. Finally, the top-level module was simulated.