| With the recent completion of the BeiDou constellation and forthcoming launches of Galileo satellites,the GNSS(Global Navigation Satellite Systems)industry is always evolving at a rapid pace,interoperable multi-gnss is the reality for the foreseeable future.The continued diverging needs of hundreds of applications drive the customisation of GNSS receivers with wide-ranging complexities,capabilities,and resource requirements.The expectations of users in different applications are often contradictory,but they do share some commonalities:The need for continuous and dependable PNT(position,navigation,time)services,and the quest for ever better performance at large,e.g.in terms of accuracy,cost,or autonomy.GNSS receivers across all domains now commonly feature multi-frequency support in order to deliver better performances to end users,primarily greater accuracy and robustness to interference.Dual-frequency receivers offer significant advantages over single-frequency receivers in terms of achievable accuracy.Compared with hardware receiver,software receiver realizes the performance of the receiver by software,and is suitable for developing new algorithms.Modern FPGAs(Field Programmable Gate Array)offer a cost-efficient alternative to ASICs(Application Specific Integrated Circuit),and provide the flexibility and scalability.To this end,this paper mainly studies the multi-frequency and multi-system gnss signal acquisition algorithm,and carries on the engineering implementation on the FPGA.This article first introduces the basic structure and system of GNSS navigation signals,reviews the status of satellite navigation now(as of October 2020),and discusses various global navigation satellite systems and regional satellite navigation systems.Next,this article compares several acquisition algorithms for GNSS signals,explores the specific principles of Squared Segmented Matched Filter-Fast Fourier Transform acquisition algorithms in detail.Finally,the FPGA platform verified the capture function of GPS L1C,BDS B1C&B2a,Galileo E1OS and GLONASS L1OC signals.The simulation results show that the algorithm proposed in this paper can effectively capture the signal,the implementation of hardware FFT can increase the processing speed by 20%,and the receiving device implemented in the receiver FPGA accounts for 40%of the total area of the FPGA,which can solve our country’s autonomous navigation chip to a certain extent.The single-function and GNSS high-precision,high-reliability location service system has long been constrained by complicated foreign issues. |
