无星历条件下的快速频差计算方法设计

Research on the Design of Fast Frequency Difference Calculation Method under Ephemeris-free Condition

在载波剥离前,需对卫星信号进行捕获,捕获后可得到卫星信号多普勒频移、伪码相位的估计值。快速频差获取方法使得在定位解算之前就能完成校频,并很大程度上缩小信号搜索范围,有利于捕获方法的快速收敛。本文设计了无星历条件下的卫星多普勒异常剔除方法,该方法考虑所有卫星载波多普勒都存在一个共同的频差特性,利用该特性可估算出所有卫星载波多普勒粗略值,从而缩小搜索范围,减少捕获时间。通过对本文算法的半实物仿真可知,该算法在无须预先获取卫星星历的条件下,相较于传统的定位后较频方法,算法收敛时间减少约25s,同时频差误差值在±5m/s以内。

Capturing satellite signals before carrier stripping can obtain estimates of Doppler shift and pseudo-code phase.The fast frequency difference acquisition method makes it possible to complete the frequency calibration before the positioning solution and to narrow the signal search range to a large extent,which is conducive to the fast convergence of the capture method.Accordingly,this paper proposes the design of a satellite Doppler anomaly rejection method under ephemeris-free conditions,which employs the common frequency difference property to estimate the rough value of all satellite carrier Doppler,thus narrowing the search range and reducing the capture time.The semi-physical simulation shows that compared with the traditional post-positioning frequency comparison method,the convergence time of the algorithm is reduced by about 25 s and the frequency difference error is within±5 m/s without obtaining the satellite ephemeris in advance.