Research On The Fast Acquisition Algorithm Of High Dynamic GPS Signal

Possessing the largest number of users and having the advantages of high accuracy,high university,as well as the simple receivers for users,the Global Positioning System is the most popular and perfect system worldwide.It has been applied in many areas such as positioning and navigation,basic mapping,precision orbit determination.Currently,the way how to improve the performance of GPS receivers to ensure high-precision and real-time is the research hot spot.The key technologies are rapid and efficient signal acquisition and tracking.This paper studied primarily on the problem of rapid acquisition for high dynamic signals in GPS receiver.Through a detailed analysis on the principle of acquisition algorithm and the structure of hardware implementation representatively,a new improvement scheme was presented in order to reduce the computing volume and the complexity of implementation.This paper simulated a kind of satellite signal,which can describe each satellite signal transmitting in different environment with separate SNR,on the basis of understanding the GPS signal forming principle. These simulation signals were used to provide necessary support for acquisition algorithm verification.The advantages and disadvantages about sliding correlation method and FFT capture algorithm were analyzed in the paper.A novel method of capturing the GPS signal based on the theory of spectral correlation is presented.The cyclic spectrum of GPS IF(intermediate frequency) signal is estimated by means of frequency-domain smoothing symmetrical periodogram.Through analyzing the magnitudes,phases and positions information of cyclic spectrum,an estimation of carrier frequency,chip rate and initial phase is complemented.This estimation method,which can weaken the affection of stationary noise and interference,is suit to the situation of low-SNR.Moreover,it is computationally efficient due to avoiding multi-dimensional search and has a high estimating accuracy.The FFT acquisition method in frequency domain with less computing volume and more difficult implementation was studied in this paper and the top level implementation scheme was provided,as well as the frameworks of sub-modules.A reasonable quantify method was designed and a sampling and averaging device was introduced.Through synthesis and simulation processed by Quartusâ…¡8.1 and Modelsim-Altera6.3g,the simulation results verified the functional efficiency.This scheme simplified the hardware and accelerated the processing speed,thus achieve a faster signal acquisition.