测距码结构监测是信号监测系统的重要组成部分,但接收的信号往往淹没于噪声中,无法从时域中提取出测距码序列。推导了BOC信号的通用自相关与功率谱密度的表达式,并提出了一种适用于低信噪比下的BOC信号测距码解码方法。该方法利用导航信号的循环平稳特性与噪声的平稳特性,通过谱相关理论估计信号的多普勒和码速率,取小于一个码周期的数据与原始数据滑动相关去除电文的影响,然后剥离副载波恢复出测距码的时域波形,通过仿真分析BOC(1,1)信号验证了算法的有效性。

Ranging code monitoring is one of the most important functions of signal monitoring system. However, the received signal is often buried in noise, and the ranging codes are not visible in time domain. The autocorrelation and power spectral density functions of BOC signal were derived, and a BOC ranging code decoding method was proposed in low SNR. In this method, Doppler frequency and code rate were estimated by spectral correlation theory based on signal's cyclostationarity and noise's wide sense stationary. After wiping off the Doppler shift, navigation message bits were determined and removed by slide-correlating a small slice of itself with the whole data. The start of the code was determined by stacking multiple periods of the whole data into a code period, and then the whole data was shifted to the start of the PRN code, and was restacked. Then the individual period of PRN codes was estimated after wiping off subcarrier. This method was verified by simulating BOC(1,1) signal.