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

A technology of frequency offset and signal acquisition, which is applied in the field of global navigation satellite systems, can solve the problems of affecting the acquisition performance and the inapplicability of weak navigation signals

Active Publication Date: 2013-03-20
TSINGHUA UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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

Method used

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

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Embodiment

[0120] In this embodiment, the carrier frequency is 1575.42MHz, the sampling rate is 62MHz, the intermediate frequency frequency is 46MHz, the pseudo code rate is 10.23Mchip / s, the coherent integration time is 2ms, the number of incoherent accumulation times is 10, and the frequency range of the carrier to be searched is -5kHz. Taking 5 kHz as an example, the implementation steps of the weak GNSS signal acquisition method under large-scale frequency offset of the present invention are further described:

[0121] 1. According to the coherent integration time of the receiver, the number of incoherent accumulations, the carrier frequency, and the sampling rate, determine that the step size of the rough carrier frequency search is 1270Hz.

[0122] 2. With 1270Hz as an interval, divide the carrier frequency range to be searched into 8 carrier frequency cells. Let the frequencies of these carrier frequency cells be -5000+1270k (k=0, 1, 2, . . . , 7) respectively.

[0123] 3. Accord...

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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 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 broadcast satellite signals to users around the world in a code division multiple access manner. In this way, the user can receive satellite signals normally only after completing the pseudo code capture. In cities, mountains, forests and other environments, satellite signals are often blocked by surrounding buildings, vegetation, etc., the signal will become very weak, and pseudocode capture will become very difficult. Further, when the user's motion...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01S19/24G01S19/30
Inventor 李洪陆明泉冯振明
Owner TSINGHUA UNIV
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