The missile's velocity,acceleration and jerk are quite high,and the linear and quadratic variation rates of Doppler frequency shift are great.Conventional carrier tracking loop can lose lock,and stable carrier tracking is a key factor for the GNSS receiver to work under high dynamic environment.Based on the conventional FLL-assisted PLL tracking loop,a weighting factor carrier tracking method is proposed,which is assisted by Four-Quadrant Frequency Discriminator.Firstly,frequency offset of the received signal was drawn to the lower range by using the nonlinear characteristic of the FQFD.Then,the weights of FLL and PLL were adjusted by weighting factors,and the relevant parameters were determined.This weight adjustment can perform a better integration of FLL and PLL in the tracking process.The thermal noise error,the dynamic adaptability and the appropriate bandwidth were analyzed.The capability of the new carrier tracking was simulated and the result proves that whatever the time function of the Doppler frequency is,the carrier can be tracked by using the new carrier tracking loop.It can be concluded that the new carrier tracking is valid.%由于导弹的速度、加速度和加加速度都较高,多普勒频移一次变化率、二次变化率很大,常规载波跟踪环路将会失锁.稳定的载波跟踪使导航(GNSS)接收机在高动态环境下正常工作.由于常规锁频环(FLL)辅助锁相环(PLL)的跟踪环路引起失锁问题,提出一种采用四相鉴频方法辅助的加权因子载波跟踪方法.上述方法首先利用四相鉴频的非线性特性将信号的多普勒频偏快速牵引到较低的范围,然后利用加权因子调整FLL&PLL的权重,理论分析了热噪声误差、动态应力误差以及最优带宽问题,并确定环路相关参数,从而使锁频环和锁相环达到最优配合.采用数字仿真,结果表明,根据上述方法设计的载波跟踪环路在多普勒频偏为常值、阶跃函数、一次斜升函数和二次斜升函数时均能进行准确跟踪,验证了所提方法针对导弹载波信号跟踪的有效性.
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