| Satellite navigation technology is widely used in transportation,logistics,agriculture,aerospace,homeland security,land planning,basic surveying,geology and earthquake disaster monitoring.Because of its extraordinary technical significance,China must vigorously develop BeiDou satellite navigation technology in order to prevent it from being manipulated and ensure national security.Since satellite signal search acquisition time determines the performance of GPS/Beidou receivers,capturing satellite signals quickly and accurately has always been a primary issue in satellite navigation technology research.The acquisition of satellite signals is the first step in satellite navigation technology.GPS/Beidou receiver signal tracking and demodulation of navigation data bits all depend on the capture of satellite signals.In satellite acquisition,each satellite in the GPS/BeiDou constellation needs to complete two key tasks simultaneously: one is the carrier Doppler frequency shift search,and the other is the initial phase search of the spreading code.In existing capture algorithms,in order to cover all Doppler frequency ranges expected in high-speed mobile satellites,traversal searches are usually performed within 10 kHz,and parallel code phase search of GPS/Beidou satellite signals is applied,and a large number of Fast Fourier Transform(FFT)operation.Under the current commercial application of satellite navigation technology,the acquisition algorithm is basically stipulated,and coupled with the superior performance of the Fast Fourier Transform(FFT)does not seem to need improvement and improvement.In recent years,breakthroughs have been made in Sparse Fast Fourier Transform(SFFT),and its performance surpasses that of Fast Fourier Transform(FFT).Therefore,whether the global satellite navigation technology's capture algorithm can use this new technology to achieve faster capture of satellite signals has become the main research content of the paper.The following major work was completed.The first is the research phase of technical literature: First,study the composition and parameter characteristics of GPS/BeiDou satellite signals,then build a GPS/BeiDou digital IF signal source,provide the software to simulate the digital IF signal,and then perform the Matlab simulation on the SS code.Study the correlation of spreading codes.Followed by the traditional GPS/Beidou capture algorithm research phase: Study three traditional GPS/Beidou capture algorithms,including serial capture algorithm,FFT-based parallel frequency acquisition algorithm and FFT-based parallel code phase capture algorithm,and analyze its performance..Finally,we study the phase of SFFT algorithm applicable to the phase capture of GPS/BeiDou satellite signal parallel code.Firstly,we study the history and principle of SFFT algorithm.Secondly,we analyze the common techniques of SFFT algorithm,then combine the frequency domain of satellite signal with sparse characteristics and based on FFT satellite signal parallel code phase acquisition algorithm,proposed a satellite signal based on SFFT parallel code phase capture algorithm.The algorithm adopts sampling ideas with different modulus calculations and different remainders.First,the IF signal and the local code are down-sampled to obtain a subset of the IF signal and the local code.Secondly,a down sampling of the Doppler shift amount is performed to obtain A subset of the Doppler shift amount;then use the frequency domain binary search algorithm to obtain the best subset,and finally complete the parallel code phase capture of the satellite signal in the best subset.Theoretically,it is 22.91 times lower than that of FFT-based capture algorithm.Finally,Matlab simulation is performed on the algorithm using the actual satellite signal,which is 16.8598 times faster than the FFT-based parallel signal phase acquisition algorithm for satellite signals.It is proved that the proposed algorithm has low computational complexity and fast capture speed. |
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