Abstract
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.
Highlights
Using GPS system for positioning and navigation, we need to capture the GPS signal at first
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
When the starting position of the C/A code of the GPS signal is 1234 and the carrier frequency is 1,255,123 Hz, setting the signal-to-noise ratio to −10 dB, the simulation results of the acquisition of the No 1 satellite signal are shown in Figures 2-4 : 5 7
Summary
Using GPS system for positioning and navigation, we need to capture the GPS signal at first. This method is simple, but the search time is too long. The subscript s represents the satellite number, Cs is the C/A code of the satellite S, fi = 1250 − 10, 1250 − 9, ···, 1250 + 10 kHz. The local signal must be digitized at a 5 MHz sampling rate to produce 5000 data points. The above 21 sets of data (only corresponding to a satellite C/A code) represents 21 frequencies at intervals of 1 kHz. If the C/A code and the frequency of the local signal are correct, and the C/A code phase is aligned, the output is maximized. The flow chart of the acquisition process is as shown in Figure 1: Input Data
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