GNSS signal mixer-free parallel code phase capturing method

Abstract

The invention discloses a GNSS signal mixer-free parallel code phase capturing method. The method conducts FFT on signals received at N points, the transformed sequence is recorded as y1<right arrow>, and N is a power of 2. The method then conducts FFT of local code signals at N points, obtains a conjugated sequence of the transformed sequence and records the obtained sequence as y2<right arrow>. The method rotates the y2<right arrow> right for m bit positions, multiplies the y2<right arrow> with corresponding points of the y1<right arrow> and obtains a sequence y3<right arrow>, conducts inverse FFT on the y3<right arrow>, and outputs a sequence y4<right arrow>. The y4<right arrow> is rotated left for m bit positions, and an output sequence Sm<right arrow> is a coherent integration result of N different code phases at the mth frequency point. The maximum value of the envelope of the Sm<right arrow> is compared with a threshold. If the maximum value exceeds the threshold, a signal is considered to exist, and a corresponding code phase and Doppler frequency are output. The method can complete Doppler frequency searching with no need of frequency conversion of the signal first. Besides, the search precision is high, the calculation is simple, and the method is easy for implementation.

Description

technical field [0001] The invention relates to a GNSS signal frequency-mixing-free parallel code phase acquisition method. Background technique [0002] Common GNSS signal acquisition methods include: serial search method, parallel frequency search method and parallel code phase search method. The serial search method searches different code phases and Doppler frequencies in turn, which has low complexity, but requires a long search time; the parallel frequency search method uses FFT to complete the search in parallel, which is equivalent to using FFT to Spectrum analysis; parallel code phase search method, the coherent integration operation of different code phases is completed by the convolution theorem. The traditional code phase parallel search method needs to convert the frequency of the signal first to complete the Doppler frequency search, which has high computational complexity. [0003] The process of parallel code phase search can be expressed as figure 1 shown...

AI Technical Summary

Problems solved by technology

The traditional code phase parallel search method needs to convert the frequency of the signal first to complete the Doppler frequency search, and the computational complexity is high

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