Method for rapidly capturing weak signals of Beidou D1 satellite navigation system

Abstract

The invention discloses a method for rapidly capturing weak signals of a Beidou D1 satellite navigation system. The method comprises the following steps that S1, the satellite PRN numbers searched by channels are set from 1 to 6; S2, first sampling is carried out on received signals; S3, NH codes are selected for forming a matching filter to carry out relevance addition on resampling data of the received signals; S4, the results of the relevance addition in the step S3 are divided into N sections, and relevance addition is carried out on the results and local codes point by point; S5, M point FFT is carried out on the results of the relevance addition in the step S3; S6, the signal to noise ratio is calculated, whether the signals are captured or not is detected according to the threshold value of the signal to noise ratio, and if the signals are not captured, the phases of the NH codes are changed, and the step S1 to the step S6 are repeated. The method can peel NH secondary coding, achieve relevance addition of 20 ms, and improve the capacity for capturing the weak signals of the Beidou D1 satellite navigation system.

Description

technical field [0001] The invention relates to the capturing or tracking of system transmission signals, in particular to a fast capturing method for capturing weak signals of the Beidou D1 satellite navigation system. Background technique [0002] Spread spectrum communication technology is widely used in modern communication systems, especially in the field of satellite navigation. The Beidou satellite navigation system independently developed by China (hereinafter referred to as Beidou) has a signal system similar to the GPS system of the United States and the Galileo system of the European Union. For the Beidou system, in occasions with high signal-to-noise ratio (such as outdoor open environment), it is relatively easy to capture successful satellite signals and obtain information such as code phase and carrier frequency. However, in places with weak signals, such as indoors and urban streets under dense tree shade, the carrier-to-noise ratio of satellite signals is o...

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Problems solved by technology

[0003] figure 2 The method given is a time-serial frequency parallel search method based on matched filtering, which is widely used in the fast signal acquisition of satellite navigation, but because the satellite signal is modulated with a 50BPS navigation message, only 1ms correlation accumulation can be performed , the capture algorithm corresponding to this method is the common sensitivity capture algorithm. In order to improve the capture sensitivity, the core problem to be solved is to adopt the coherent accumulation of multi-ms data. Therefore, it is necessary to eliminate the influence of data bits. In 2013, Yuan Huoping proposed to use multi-ms non- Coherent accumulation is used to capture weak signals of Beidou and GPS signals. This algorithm solves the contradiction between data storage and acquisition speed, but because only 20ms non-coherent accumulation can be used, the effect on sensitivity improvement is not obvious

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