Research And Implementation Of Beidou B1 Frequency Signal Acquisition Algorithm

With Beidou satellite navigation system successfully being put into use,it's more and more important to develop Beidou navigation receiver.Signal acquisition is the key technology of BeiDou navigation receiver,the acquisition algorithm used by navigation receiver directly determines the performance of navigation receiver.So it is of great significance to study the acquisition algorithm.This paper mainly studies the Beidou signal acquisition algorithm,and implements the module of Beidou satellite signal acquisition.In the research of this paper,we firstly introduce the theory of satellite navigation and the structure of Beidou satellite navigation system B1 frequency point signal,as well as analyze the related characteristics of pseudo-random code and the composition of navigation message.The theory of signal acquisition is studied based on the above.The satellite signal acquisition algorithm such as the signal acquisition algorithm based on matched filter,the signal acquisition algorithm based on FFT and PMF-FFT(Partial Matched Filters combined with FFT)algorithm are analyzed in detail.The performance of the above three algorithms is analyzed by Matlab simulation.Secondly,this article discusses the effect of navigation message bit-flipping on signal capture.Simulation results show that the performance of three traditional algorithms is not satisfactory for capturing signals with bit-flipping.Aiming at the problem of bit-flipping affecting the acquisition performance,two improved algorithms are proposed in this paper.The first algorithm improves the acquisition algorithm based on matched filter.It is a signal acquisition algorithm based on the separation of code phase and Doppler frequency.This algorithm uses the delay differential operation and the bipolarity of the pseudo-random code to process the signal respectively,and eliminates the influence of the bit-flipping.Based on this,the code phase and the Doppler shift are separately captured.The second algorithm improves the FFT-based acquisition algorithm,uses the compensation sequence to segment the signal to be captured,weakens the effect of bit-flipping on the signal acquisition.It is a acquisition algorithm based on bit segment compensation.In this paper,several algorithms are compared in terms of capturing sensitivity and computational complexity,and the performance of the algorithm is analyzed by using Matlab.The simulation results show that the algorithm can successfully capture the frequency signal of BeiDou B1 under the condition of bit-flipping.Finally,the algorithm based on bit segmentation compensation is realized by FPGA according to the actual engineering requirements.This article divides the whole design into carrier NCO module,digital mixing module,low-pass filter module and related accumulation module.Each module has been implemented in the ISE development environment and functionally simulated by Modelsim to verify that each module is functionally correct.Then all the modules are integrated through the top module,and the whole acquisition module is simulated.The simulation shows that the module can successfully capture the frequency signal of BeiDou B1.The research provides a theoretical basis for solving the bit-flipping signal acquisition and provides the technical basis for engineering application.