北斗/GPS伪卫星定位系统主要应用在卫星信号遮挡严重的区域,能独立或辅助增强北斗/GPS卫星定位.伪卫星信号的捕获跟踪是进行定位解算的前提,针对伪卫星信号存在跟踪不稳定的情况,在详细分析了伪卫星信号生成和捕获跟踪算法原理的基础上,基于模块复用思想,提出了一种捕获跟踪一体化方案.该方案中的捕获算法采用传统的滑动捕获算法,码跟踪算法采用Early-Late算法,在信号解调的过程中采用Costas PLL载波跟踪环路.通过采集的GPS卫星信号仿真可发现跟踪稳定后即时码的能量最大,即时码保持稳定表明进入稳定跟踪状态.在FPGA硬件平台验证了该方案,并对比分析了存在多普勒频偏和无频偏情况下的性能.仿真结果表明,该方案在多普勒频率偏移下依然能够有效、稳定地跟踪解调出导航信号.%Beidou/GPS pseudo satellite positioning system is mainly used in the area of satellite signal shielding seriously and it can be in-dependent or assistant enhancement of the Beidou/GPS satellite positioning. Pseudo satellite signal acquisition and tracking is the precon-dition of positioning solution. Aiming at the situation of tracking instability for pseudo satellite signal,after the pseudo satellite signal gen-eration as well as acquisition has been analyzed in detail,an integrated scheme of acquisition and tracking based on model reuse is pro-posed. The capture algorithm is adoption of traditional sliding capture algorithm and the tracking algorithm is the Early-Late in this scheme,and Costas PLL carrier tracking loop has been employed in the process of signal demodulation. Through simulation of the GPS satellite signal,it is found that the energy of the real time code is the largest after the instant code remains stable. Experiments for verifica-tion on this scheme on the FPGA hardware platform have been conducted as well as the contrast analysis on its performances on the con-ditions of Doppler frequency offset and non-frequency offset. The simulation results show that the proposed scheme in the presence of Doppler frequency offset has operated stably and effectively in signal tracking and demodulation.
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