北斗二代B1信号载波精频捕获算法

Fine frequency acquisition algorithm of Beidou-Ⅱ B1 signal carrier

北斗卫星信号的捕获算法是北斗接收机的关键技术之一,针对北斗卫星捕获算法在提高捕获精度和降低捕获时间之间的矛盾,提出了一种在完成北斗卫星信号粗捕获以后利用载波相关得到载波精频的算法。该算法首先利用4 ms数据对卫星进行粗捕获,得到200 Hz的载波多普勒频率分辨率,然后利用本地复制伪码将载波中的伪码剥离,并且产生3个相位差一定间隔的本地载波,将这些载波与剥离伪码的本地载波进行相关运算,利用这些相关运算结果最终得到载波的精频。通过实验平台采集实测数据对算法进行验证,结果表明,该算法能够降低多普勒频率估计误差,提高捕获精度。

The signal acquisition algorithm is one of the key technologies of the Beidou satellite receiver. For the signal acquisition algorithm of Beidou satellite, there is a tradeoff between acquisition precision and time. In this paper, a new algorithm is proposed based on the carrier wave correlation to the cartier frequency after coarse acquisition of the Beidou satellite signal. In this algorithm, we first used the 4ms data to carry on the coarse acquisition to the satellite, so that the 200 Hz resolution can be obtained by the carrier Doppler fre- quency. Then the local copy of the CA code was applied to peel the CA code in the carrier and generate three phase difference of a certain interval of the local copy of the carrier. By the correlation operation of these carriers with the local carrier of the stripped CA code, the fine frequency of the carrier was calculated by using these correlation results. The simulation results show that the proposed algorithm can reduce the Doppler frequency estimation error. It also improved the acquisition accuracy.