对电文翻转不敏感的导航信号载噪比估计算法

对于导航接收机而言，获取通道信号载噪比可辅助其提升跟踪精度和定位速度。但在使用传统的宽窄带功率比值法做载噪比估计时，由于该方法对导航电文数据比特的符号翻转敏感，导致其估计精度较低且运算量大。针对这一问题，提出一种对电文翻转不敏感的导航信号载噪比估计算法，该算法立足于在通道稳定跟踪时信号能量集中在I路，且噪声能量均等分散在I、Q两路，使用I、Q路信号能量做载噪比估计。首先，通过公式推导得出其运算表达式，再经计算机仿真确定最佳的单次积分时长和运算组数。结果表明，相较于宽窄带功率比值法，虽然该算法总积分时间略长，但对导航电文翻转不敏感，估计精度可提升5.72 dB或更高。在总积分时间相等的条件下，算法运算量相较于宽窄带功率比值法降低了33.6%。所提算法不仅提高了估计精度，同时降低了运算量，在导航接收机中有一定的应用前景。

A navigation C/N0 estimation algorithm insensitive to message flipping

For navigation receivers, obtaining channel signal C/N0 can assist them to improve tracking accuracy and positioning speed. However, when the traditional wire-narrow-band power ratio method is used to estimate the C/N0, the estimation accuracy is low and the computation is large because the method is sensitive to the flip of navigation message. In order to solve this problem, this paper proposes a navigation signal C/N0 estimation algorithm which is insensitive to message flip. Based on the feature that the signal energy is concentrated in I channel and the noise energy is equally dispersed in I and Q channels, the algorithm uses the signal energy of I and Q channels to estimate the C/N0. In this paper, the calculation expression is derived by formula, and then the optimal single integration time M and the number of operation groups K are determined by computer simulation. Compared with the wide-narrow band power ratio method, the total integration time of the proposed algorithm is slightly longer, but it is not sensitive to navigation message flipping, and the estimation accuracy can be improved by 5.72dB and more. When the total integration time is the same, the computational cost of the proposed algorithm is reduced by 33.6% compared with the wide-narrow-band power ratio method. The algorithm proposed in this paper improves the estimation accuracy and reduces the computation, and has certain application prospects in navigation receivers.