Method and system for capturing weak GNSS (Global Navigation Satellite System) signal under condition of large-scale frequency deviation

Abstract

The invention discloses a method and a system for capturing a weak GNSS (Global Navigation Satellite System) signal under the condition of large-scale frequency deviation. The method comprises the following steps of: according to a pre-detection integration time, a carrier frequency and a sampling rate, determining a maximum carrier frequency searching step; dividing the whole frequency range to be searched into a plurality of carrier frequency units according to the maximum frequency searching step to realize rough search of the carrier frequency; mapping a received satellite signal onto each carrier frequency unit and regulating a local pseudo code rate according to the carrier frequency units so as to reduce the influence of code Doppler; calculating correlation in a flexible zero-padding mode through FFT (Fast Fourier Transform) / IFFT (Inverse Fast Fourier Transform) so as to realize code phase parallel search; and carrying out FFT operation on different correlation values corresponding to the same code phase so as to fulfill the aim of carrying out fine search on the carrier frequencies in the carrier frequency units. By the method and the system, a capturing speed and a capturing sensitivity of a receiver can be improved, so that the receiver completes the work of capturing a weak navigation signal pseudo code under the condition of the large-scale frequency deviation.

Description

technical field [0001] The invention relates to the technical field of Global Navigation Satellite System (GNSS), in particular to a weak GNSS signal acquisition method and system thereof under large-scale frequency offset. Background technique [0002] Global Navigation Satellite System (GNSS) mainly includes Global Positioning System (GPS) (United States), Global Navigation Satellite System (GLONASS) (Russia), Galileo Navigation Satellite System (GALILEO) (EU) and Beidou Global Navigation System (COMPASS) (China) ). These systems all broadcast satellite signals to users around the world by way of code division multiple access. In this way, the user must receive the satellite signal normally after completing the pseudo-code capture. In environments such as cities, mountains, and forests, satellite signals are often blocked by surrounding buildings, vegetation, etc., the signal will become very weak, and it will become very difficult to capture pseudo codes. Furthermore, ...

AI Technical Summary

Problems solved by technology

Code Doppler will cause relative slippage of the code phase between different signal segments, so that the correlation peaks of different signal segments cannot be accumulated on the same code phase, which will seriously affect the acquisition performance

Therefore, the above algorithm is not applicable to weak navigation signals, and it is urgent to study new methods

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