Beidou signal capturing method in weak signal environment

Abstract

The invention relates to a Beidou signal capturing method in a weak signal environment. The method comprises the following steps: S1, arranging a down-conversion unit and carrying out down conversion processing on a received intermediate-frequency sampling signal; S2, carrying out NH code stripping on the received signal respectively, carrying out transformation into a frequency domain signal, carrying out multiplying with a multiplexing sum of a local code frequency domain value and then carrying out inverse transformation into a time domain; S3, carrying out conjugate multiplication on a coherent accumulation value at current time and a coherent accumulation value at previous time and carrying out summation; and S4, carrying out taylor series expansion on an amplitude difference value of two-side spectral lines of the peak value of the coherent integration result, deriving a quasi-linear relation of a frequency value and the amplitude difference value, and solving a frequency estimation value by using the linear relation. According to the invention, correlation calculation can be carried out on coherent values corresponding all code phases by one time; the signal to noise ratio is improved and the detection efficiency is improved; and the squaring loss of the non-coherent integration can be reduced. A problem of bit flipping caused by navigation data modulation can be solved, thereby improving the detection probability; the code phase and carrier wave frequency-offset estimation precision is enhanced; and the calculating speed and the calculating precision are guaranteed and the good stability and practicability are realized.

Description

technical field [0001] The invention belongs to the technical field of navigation signal detection, in particular to a Beidou signal acquisition method, which can be used for Beidou weak signal acquisition. Background technique [0002] The Global Navigation Satellite System (GNSS) signal is a spread spectrum signal that has been modulated by direct sequence spread spectrum. The acquisition of the satellite navigation signal that has been modulated by direct spread spectrum is the primary problem that the GNSS system needs to solve. When the signal conditions are not ideal, such as indoors, forests and urban environments, the phenomenon of occlusion, multipath and interference is more serious, the energy is more weakened and fading, and the receiving signal-to-noise ratio is deteriorated to a greater extent. Ordinary acquisition methods will be difficult to capture and track navigation satellite signals. At present, the main problem solved by serial / parallel algorithm, fast...

AI Technical Summary

Problems solved by technology

GNSS improves the signal-to-noise ratio by lengthening the time of coherent integration and non-coherent integration, thereby improving the sensitivity of signal detection.

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