一种GNSS信号跟踪环路频相直调控制算法

全球卫星导航系统(Global Navigation Satellite System,GNSS)接收机信号跟踪环路正确地锁定导航信号的频率、相位是提取测量值以及导航星历的基础。传统的接收机跟踪环路采用调整频率的方式来调整相位,不能及时消除跟踪误差,并且在弱信号条件下容易受到噪声影响,难以对信号进行精确跟踪。针对这一问题,提出了一种基于非相干预滤波器的频相直调环路控制算法,采用非相干预滤波器提取跟踪误差,并且在本地信号生成阶段直接将载波相位差、载波频率差、码相位差进行消除。实验表明,与传统环路相比,频相直调算法对载波相位、码相位迁入速度分别提高了90%和95%,高动态、弱信号下多普勒估计精度分别提高了69.25%和61.37%,并且频相直调算法能够有效抑制环路参数调整、载体突然机动对载波相位锁定带来的扰动。

A Direct Frequency-Phase Adjustment Algorithm for GNSS Signal Tracking Loops

The phase and frequency lock for received global navigation satellite system(GNSS) signal is the pre-condition of measurement formulation and navigation data demodulation for GNSS receiver.The traditional GNSS signal tracking loop adjusts the phase of local signal through frequency adjustment(FA).This method cannot eliminate the tracking error timely and accurately.For this problem,this paper proposes a direct phase-frequency adjustment(DPFA) algorithm based on non-coherent pre-filter.The non-coherent pre-filter is employed to estimate the tracking error accurately,while the DPFA is exploited to eliminate the tracking error timely.Different experimental scenes are designed to show the advantages of DPFA over FA.Compared with traditional signal tracking loop,the DPFA can improve the carrier phase and code phase pull-in speed by 90% and 95%respectively,the Doppler estimation accuracy in high dynamic and weak signal scene by 69.25% and 61.37% respectively.The DPFA can also decrease the disturbance caused by coefficients adjustment of tracking loop,and abrupt maneuver of vehicle.