Galileo系统L1P与L1F信号间干扰的分析

Interference Analysis between L1F Signals and L1P Signals of Galileo System

在L1频段上,Galileo系统的授权服务信号L1P和开放服务信号L1F共用中心频点1 575.42 MHz,它们的功率谱部分重叠,相互之间存在干扰。通过仿真研究L1P和L1F信号间的干扰,对它们的干扰系数、载噪比衰减值进行了详细分析,找出了决定这两种信号间干扰大小的主要因素。仿真结果显示,L1P信号受到来自于L1F信号的最大干扰为0.002 dB,来自于CDMA干扰的最大值为0.26 dB;L1F受到来自于L1P信号的最大干扰几乎为0 dB,来自于CDMA干扰的最大值为0.604 dB。这表明,CDMA干扰是主要干扰源,L1P和L1F信号间的干扰可以忽略。这主要受益于L1P信号采用余弦相位的BOC调制,L1F信号采用CBOC调制,使这两个信号的功率谱重叠部分大大减少,从而干扰系数很小,大大减小了它们间的干扰。

The Galileo system transmits L1P signal （for public regulated service） and L1F signal （for open service） at a center frequency of 1 575.42 MHz in L1 band. The interference between each other is inevitable due to power spectrum overlap. In this paper, the interference between L1F and L1P signal is researched, the interference coefficient and the CNR（ Carrierto- Noise Ratio） degradation are analysed, and the main factors determing the strength of the two types of signal are found out. Simulation results show that, the L1P sign~ suffers about O. 002 dB the maximum interference created by the L1F signal, and about 0.26 dB by the maximum Code Division Multiple Access（CDMA） interference; the L1F signal suffers almost negligible interference from the LIP signal and about 0.604 dB the maximum CDMA interference. The result indicates that, the CDMA interference is preponderant and drives the total degradation of intra-system degradation, and the interference between LIP and L1F signal is almost negligible. This mainly benefits from L1P signal using cosine phase of Binary offset Carrier（BOC） modulation, and L1F signal using Composited Binary offset Carrier（CBOC） modulation, so that the power spectrum of the two signals overlap greatly reduces, the interference coefficient is very small, greatly reducing the interference between them.