基于FPGA的BOC(1,1)信号捕获技术

Technique of BOC(1,1) Signal Acquisition Based on FPGA

关键词:  BOC调制  ASPeCT技术  信号捕获  FPGA

Key words:  BOC modulation  ASPeCT  Signal acquisition  FPGA

摘要:

BOC调制是新一代卫星导航系统中广泛采用的调制方式,在时域上具有多峰值特性,副峰的存在增加了捕获的难度。采用自相关副峰消除技术(ASPeCT）在原有的BOC码相关支路的基础上增加一条伪码相关支路,可以有效削弱码相位检测函数的副峰,避免误捕获,是一种性能良好的BOC信号捕获技术。提出一种采用二维并行快速搜索的在FPGA芯片中实现ASPeCT捕获技术的方案,可以显著缩短捕获时间。在理论分析和仿真验证的基础上,采用Verilog硬件描述语言在接收机FPGA+DSP平台上编程实现,在露天测试中,成功捕获到Galileo E1B卫星导航信号,并对ChipScope采集的数字中频信号的多普勒频率和码相位静态捕获结果进行验证,与同一段信号的Matlab仿真结果一致,证明所提出的技术方案正确合理可行。

Abstract:

BOC modulation will be widely adopted in new satellite navigation system. The signal has multi-peaks in time domain. The existence of side-peak increases the difficulty of acquisition. Autocorrelation side-peak cancellation technique (ASPeCT) is good in performance as it can effectively weaken the side-peak of code-phase detecting function and avoid false lock by adding a pseudo-code detecting branch on the basis of one BOC-code detecting branch. An implementation project of 2-D parallel fast search for ASPeCT on the FPGA chip is put forward which can significantly cut the acquisition time.On the basis of theoretical analysis and emulation verification, the acquisition algorithm is realized by Verilog HDL programing on FPGA+DSP receiving platform. The Galileo E1B satellite navigation signal is successfully acquired in the open air test. The Doppler frequency and code phase static acquisition results of the digital IF signal captured by ChipScope fall in line with the Matlab simulation results of the same signal, which proves the validity and feasibility of the project put forward