Since the global positioning system began to operate, it has become more and more close to people’s lives, and has been applied to various fields now. In order to track and decode GPS signals, GPS signals need to be captured first. The necessary parameters of the captured GPS signal are immediately transmitted to the tracking process, and then the navigation message of the satellite can be obtained by tracking process. In this paper, the basic contents related to the signal structure of GPS system are briefly described. Then, the traditional GPS signal acquisition method based on time domain correlation method is introduced, and the GPS signal acquisition method based on FFT cyclic correlation method is discussed in this paper. By comparing the simulation results, two kinds of GPS signal acquisition methods are compared with the calculation time according to the method of controlling variables. For the two GPS signal acquisition methods, the variation of time delay error with SNR is simulated in this paper.

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Fast Acquisition Method of GPS Signal Based on FFT Cyclic Correlation

The method changing non-coherent integration to coherent integration is proposed to increase the sensitivity of signal acquisition. A phase jump occurs between the consecutive blocks when the carrier frequency is circularly shifted and this leads to the problem of direct accumulation. A compensation factor is exploited to solve the problem. Monte Carlo simulation results show that the method can improve the sensitivity of acquiring weak signals.

High-sensitive acquisition of signals for inter-satellite links of navigation constellation

This paper analyzed the influence of the bit transition to acquire the weak GPS signal. To improve the acquisition performance, an algorithm based on the differential coherent and half-bit algorithm was proposed. The proposed method involves a differential correlator and the half-bit coherent operation to eliminate the attenuation brought by the bit transition, and a frequency domain technique is also introduced to reduce the computational complexity. The theoretical analysis and simulation results show that the detection sensitivity is improved about 1.7dB compared with the FMDBZP method, and 1.9dB compared with the DCC method.

A high performance weak-GPS-signal-acquisition technique based on half-bit method

Acquisition module is an important part in GPS receiver. Three current acquisition methods are introduced, and on the basis of parallel frequency search, a new algorithm that changing step length and quadratic curve fitting in frequency domain is given to improve the precision of acquisition. At the same time, parallel frequency search and parallel code phase search are combined to implement code phase acquisition and the high precision of acquisition on Doppler frequency offset. The simulation result shows that the acquisition error can be controlled in a smaller scope at different SNRs through the method given in this paper.

A high precision acquisition algorithm of GPS based on parallel frequency search

On the basis of average periodogram algorithm in this paper proposes an improved algorithm towards implementation in deep space. By changing the sample length in FFT calculation, the improved algorithm weakens the inuence of symbol overturn and corrects the procedure of parameter design. The simulation result denotes: when Eb=N0is 1.5dB, dopper frequency in (-300, 300)kHz, Doppler frequency gradient in (-800, 800)Hz/s the improved algorithm can make sure the acquisition propability reaches 90% with the cost of increasing calculation quantity. Copyright © 2015 Binary Information Press.

http://ir.nssc.ac.cn/bitstream/122/5266/1/201511217993-8001.pdf

The coarse carrier synchronization algorithm used in deep space communication

To improve speed and accuracy of the GPS signal acquisition,a new parallel acquisition algorithm based on FFT is proposed.The new algorithm only takes one time of FFT and multiple times of IFFT to complete the two-dimensional search,and operation time reduces the half as compared with that of the traditional algorithm based on FFT.A new algorithm based on polynomial interpolation is proposed to improve the precision of the acquisition accuracy after the coarse acquisition.Simulation results prove it well.

X Chen

Papers

A new rapid acquisition algorithm based on FFT for GPS signals