Method for capturing full bit of GPS weak signal

Abstract

A whole bit acquisition method for GPS weak signals relates to the acquisition treatment of a receiver in GNSS, and solves the problems that the prior software receiver can not forecast the information bit reversal, thereby easily causing the failure of the acquisition, and the better acquisition effect is difficult to achieve by adopting the differential coherent cumulative method. 20 sequences which are compressed into 4096 sampling points are acquired after satellite signals are subjected to the treatments related to frequency mixing, sampling, quantifying and time-domain averaging; the IFFT calculation is carried out after multiplying the 20 sequences with the sequences which are conjugated with the local stored pseudo-code FFT sequences through the FFT calculation; the maximum value which is obtained by the extraction after the mod squaring of the 20 two-dimensional pseudo-code auto-correlation value matrix is compared with a threshold value sigma 1, if the maximum value is larger than the sigma 1, the acquisition is successful; if the maximum value is smaller than the sigma 1, the whole bit algorithm is utilized to seek a peak value of the extracted related values by carrying out the coherent accumulation and the non-coherent accumulation of the 20 two-dimensional pseudo-code auto-correlation value matrix after the information bit reversal, the peak value is compared with the threshold value sigma 2, if the peak value is larger than the sigma 2, the acquisition is successful; and if the peak value is smaller than the sigma 2, the re-acquisition is carried out.

Description

technical field [0001] The invention relates to the capture processing of receivers in GNSS (Global Navigation Satellite System), in particular to the weak signal capture technology of GPS (Global Positioning System) single-frequency civilian software receivers. Background technique [0002] At present, under the condition of low signal-to-noise ratio, the acquisition techniques for weak GPS signals mainly include A-GPS (Assisted Global Positioning System) and frequency-domain block acquisition methods based on FFT (Fast Fourier Transform). A-GPS uses cellular base stations to assist receivers to capture GPS signals; the frequency domain block capture method based on FFT mainly uses the principle that time domain convolution is equivalent to frequency domain product. The best method for receiving GPS signals is the matched filtering method, which is to convolve the received GPS signals with the local C / A code (pseudo-random code) sequence. It is too large, so use FFT to tra...

AI Technical Summary

Problems solved by technology

In order to further improve the signal-to-noise ratio, the current software receiver does not predict information bit flips, but directly predicts each The local C / A code period autocorrelation value matrix is ​​accumulated. If a bit flip occurs during the accumulation process, it will offset a lot of signal-to-noise ratio, resulting in capture failure.

In order to avoid the bit flip problem, the differential coherent accumulation method is used, but it is difficult to achieve a better capture effect when the signal-to-noise ratio is extremely low and the capture time is limited

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