采样频率偏移对卫星导航接收机的影响

Effects of sampling frequency offset on satellite navigation receivers

为避免采样频率偏差给卫星导航接收机带来的符号位滑动、伪随机噪声码相位移动和载波相位偏差等问题,提出了一种改进的频率偏差估计方法.接收机的码跟踪环路以码速作为时间基准,对采样频率实际值与标称值之间的偏差进行跟踪,环路稳定后得到该偏差的估计值,其采样频率的准确度可提高到10-7量级.将该估计值补偿到载波锁相环中,可减小由采样频率偏差带来的相位误差和多普勒频移偏差,从而使得导航接收机能正确解调信号,进一步提高了输出载波相位的准确度,为实现更高精度的定时和定位提供了可能性.

In order to avoid such problems as symbol sliding, phase shift of pseudorandom noise code and carrier phase offset, an improved method of frequency offset estimation is proposed. By adopting code rate as timing benchmark, the code tracking loop in the receiver tracks and calculates the sampling frequency offset between the actual and nominal values. By compensating the offset to the carrier phase lock loop, it is possible to reduce the phase offset and Doppler deviation, correctly demodulate in the navigation receivers and enhance the accuracy of the timing and position determination.