航天GPS接收机信号搜索捕获策略

航天GPS接收机的无辅助冷启动时间是一项重要指标,研究近地轨道应用的12通道C/A码导航型接收机减小冷启动时间的方法.分析GPS信号的多普勒频率和伪码相位搜索方法、捕获检测器及其参数选择、多普勒频率搜索步长和伪码搜索速率, 得到多普勒频率搜索步长为500?Hz,伪码搜索速率为475码元/s.研究轨道倾角、轨道高度、GPS天线仰角和轨道偏心率等因素对多普勒频率搜索范围的影响.阐述根据GPS卫星间夹角的统计信息选择合理的卫星分配方法.分析和仿真结果表明,根据GPS卫星间夹角的统计信息选择合理的卫星分配方法,可将冷启动时间减少25%~30%,影响多普勒频率搜索范围的因素按程度依次为:轨道倾角、轨道高度、GPS天线仰角和轨道偏心率,再考虑这些因素时可将冷启动时间减少25%~40%.

Strategy of signal search and acquisition in spaceborne GPS receiver

Unaided cold start time is an important performance of spaceborne global position system(GPS) receiver. Reduction of cold start time was developed for C/A code navigation receiver on low earth orbit(LEO). The search method of frequency and code phase, signal detector and parameters select, doppler bin, and code search speed were analyzed. Doppler bin of 500?Hz and code search speed of 475 chips/s were obtained. The orbital inclination, orbital altitude, elevation of GPS antenna and orbital eccentricity were researched as the influential factors to doppler range. GPS satellite allocation according to statistical information of angle between GPS satellites was discussed. Analysis and simulation shows that the cold start time is reduced by 25%~30% through this GPS satellite allocation method, the influential factors of doppler range are orbital inclination, orbital altitude, elevation of GPS antenna and orbital eccentricity in regular order with an effect, the cold start time is reduced by 25%~40% farther considering these influential factors of doppler range.