扩频信号捕获过程中信息比特跳变对载波频率估计的影响

扩频信号捕获过程中，信息比特跳变会使积分增益下降，载波频率估计出现偏差，导致捕获概率降低，捕获时间增长。分析了在码相位对齐的情况下，信息跳变发生在不同位置时，积分结果最大点处对应的载波频率与实际载波频率的差值。分析结果表明，信息跳变位置确定后，频率的差值与积分时间T成反比，最大可以达到0.75/T Hz，可能超出载波跟踪环路的牵引范围，进而导致环路不能入锁。针对此问题，提出了一种简便的解决方法。

Influence of Reversal of the Information Bit on the Impact of Carrier Frequency Estimate During the Acquisition of Spread Spectrum Signal

During the acquisition of spread spectrum signal, integration gain would be reduced and estimate of the carrier frequency would be mistaken, if reversal of information bit was met. As a result, probability of acquisition will fall and longer time will be taken. Error in the carrier frequency estimate is analyzed, on the assumption that the local code phase is right. It is shown that the error lies in inverse proportion to the integration time T, when the position of the reversal is acknowledged. In the worst case, it can reach 0.75/T Hz, and the tracking loop can not begin to work. In the end, an easy way to solve this problem is brought forward.