基于MBOC调制的北斗导航信号的多径误差分析

Multipath error analysis of the COMPASS navigation signal with MBOC modulation

为了定量地分析MBOC(Multiplexed binary offset carrier)调制的北斗导航信号的多径误差,在分析MBOC调制信号原理的基础上,建立了相应的多径信号模型,利用超前减滞后功率鉴相器和反正切函数鉴相器,推导了多径效应导致码相位跟踪误差和载波相位误差的表达式.对不同的多径直达幅度比(Multipath todirect ratio,MDR)、相关器间隔、前端带宽时MBOC调制信号的多径性能进行了仿真,并针对存在噪声干扰时的码跟踪误差进行了仿真分析.仿真结果表明,多径直达幅度比由-3 dB减小到-6 dB时,所产生的多径误差包络也相应地减小.在多径直达信号幅度比(MDR)一定时,采用窄相关技术和较宽的接收机前端带宽均能很好地抑制多径误差.存在噪声干扰时,码跟踪误差随着载噪比(Carrier to Noise Ratio,CNR)的增加逐渐减小为0.

In order to quantitatively analyze the multipath error COMPASS navigation signal with MBOC modulation,this paper introduces the principle of the multiplexed binary offset carrier（MBOC）,establishes the corresponding multipath signal model,and achieves the formulas of the code tracking error and carrier phase error due to multipath signals using early minus late power（EMLP） discriminator and arctangent discriminator.The multipath performance of MBOC modulated signal is simulated under different multipath-to-direct ratio,correlator spacing,front-end bandwidth,and code tracking error is analyzed in the presence of noise interference.The simulation results demonstrate the corresponding multipath error envelope decreases with multipath to direct ratio decreasing from-3 dB to-6 dB.When MDR is a constant,the multipath error can be well suppressed by applying narrow correlator technology and wider receiver front-end bandwidth.Code tracking error decreases to 0 as the carrier to noise ratio increasing in the presence of noise interference.