Long code capture system and method based on partial matched filtering FFT algorithm

Abstract

The invention discloses a long code capture system and method based on a partial matched filtering FFT algorithm. The system comprises a signal receiving and storing module, a local pseudo code storage module, a partial matched filtering module, a single code element accumulated value buffer module, an FFT module, a two code element direct coherence accumulation module, a two code element processing coherence accumulation module, a cell incoherence accumulation module, a peak value comparison module and a judgment module. The method comprises the steps of obtaining baseband signals, conducting partial matched filtering operation, conducting FFT, conducting coherence accumulation on different weights of two code elements, conducting cell incoherence accumulation, comparing peak values and judging whether the peak values exceed a judgment threshold. By means of the long code capture system and method, the long code capture performance of satellite navigation signals in an environment with a large Doppler shift and a low signal to noise ratio is improved; hardware resources captured by long codes are saved.

Description

technical field [0001] The invention belongs to the field of communication technology, and further relates to a long code acquisition system and method based on a partial matched filter fast Fourier transform (Fast Fourier Transformation FFT) algorithm in the field of satellite navigation technology. The invention can be used to realize the long code capture of the satellite navigation signal in the weak signal environment, and improve the long code capture performance of the satellite navigation signal in the weak signal environment. Background technique [0002] With the improvement of the navigation and positioning system, the application range of the navigation and positioning system is also becoming wider and wider. It is very difficult to correctly capture the long code of the satellite navigation signal in China. In this context, how to improve the long-code acquisition performance of satellite navigation signals in weak signal environments has become an increasingly...

AI Technical Summary

Problems solved by technology

The method of this patent application is mainly to perform fast Fourier transform FFT on the down-converted and sampled navigation signal and the local pseudo-code, perform frequency-domain correlation calculation, differential coherent integration and peak detection of the satellite navigation signal and the local pseudo-code, and Perform frequency compensation through circular shift search, detect and record the maximum peak value, and compare the obtained peak value with the detection threshold, so as to realize the correct capture of code phase and frequency. The disadvantage of the method disclosed in this patent application is that the calculation amount of circular shift Large, under the condition of Doppler frequency shift, the success rate of signal acquisition is low

The system of this patent application includes a digital down-conversion module for realizing digital down-conversion operation of satellite digital intermediate frequency signals, an average sampling and block accumulation module for averaging satellite data and completing block accumulation functions, and an FFT module for realizing code phase frequency domain search. Doppler circular shift search replaces the circular shift module of frequency compensation to store and store the local PRN code FFT conjugate memory of the local PRN code FFT conjugate result, the complex multiplier module to realize signal despreading, and calculate the phase correlation results of different codes The IFFT module, the differential coherent integration module for differential correlation energy accumulation of despread satellite signals, the peak detection module for signal capture and output, and the timing control module for controlling the timing of each module in the system. The functions of these modules are limited to navigation Signals and local pseudo-codes use linear frequency-domain correlation operations and linear differential coherent integration, and matrix operations of frequency-domain correlation and linear differential coherent integration cannot be realized. The disadvantage of the system disclosed in this patent application is that satellite navigation signals and local pseudo-codes The code uses linear frequency domain correlation operation and linear differential coherent integration, resulting in slow data processing speed for satellite navigation signals captured in long codes

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