一种基于频率补偿的GPS位同步方法

GPS bit synchronization method based on frequency compensation

针对GPS接收机在跟踪过程中由频率误差引起的位同步概率下降问题,提出了一种基于频率补偿的GPS位同步方法.分析了环路中频率误差引起相干积分累加值衰减的机理,利用不同频率的复信号分别对相干积分结果进行补偿,计算出20个候选位置的值,最大值对应的位置即为数据边界位置.该方法有效减少了由频率误差导致的相干累加损耗,提高了位同步的概率.在弱信号情况下,使用非相干积分方法可进一步提高信号增益和位同步概率.与其他位同步方法相比,所提方法可容忍更大的频率误差,即使跟踪环路处于失锁状态也能准确实现位同步,且在频率误差小于25 Hz的情况下表现出更优的位同步性能.

In order to cope with the degradation of the bit synchronization probability of GPS （global positioning system）receivers caused by frequency deviation during the tracking stage,a bit synchro-nization method based on frequency compensation is proposed.The attenuation mechanism of the ac-cumulation of coherent integration caused by frequency deviation is analyzed.By compensating the coherent integration results with complex signals of different frequencies,20 candidates are calculat-ed,and the maximum is on the data edge.This method can effectively reduce the attenuation of co-herent accumulation caused by frequency deviation and improve the probability of bit synchroniza-tion.In the weak signal environment,non-coherent integration is used to further improve the signal gain and synchronization probability.Compared with other bit synchronization methods,the pro-posed method can tolerate larger frequency deviation and achieve bit synchronization even if the tracking loop is in unlocked status.Besides,it shows better bit synchronization performance when the frequency deviation is less than 25 Hz.