高动态GPS卫星信号混合载波跟踪算法设计

Design of High Dynamic GPS Signal Multi Carrier Tracking Algorithm

高动态运动环境会给GPS卫星信号带来很大的多普勒频移及其变化率,甚至产生频率的突变,单一的锁相环、锁频环、四象限鉴频器无法进行稳定跟踪。在对传统锁相环、锁频环原理及性能分析的基础上,设计了一种基于Costas锁相环(Costas-PLL)、叉积锁频环(CP-FLL)及四相鉴频器(FQFD)并能够智能切换的混合载波跟踪算法,该算法基于二阶FLL辅助三阶PLL的跟踪环路实现,依据不同的动态环境使FLL和PLL交替工作,以提高载波跟踪环路的动态适应性。通过固定频率、频率一次斜升、频率二次斜升和频率突变等4种不同动态条件下的实验,证明了该算法在高动态环境下的有效性和可靠性。

High dynamic environment bring with great Doppler shift and rate of change, even with frequency break to GPS signal. Therefore, single Frequency-Locked Loop （FLL）,Phase-Locked Loop （PLL） or Four-Quadrant Frequency Discriminator （FQFD） can not achieve steady tracking. Based on the analysis of the principle and performance of traditional FLL and PLL,a multi carrier tracking algorithm which is based on Costas-PLL,Cross Product FLL（CP-FLL）,as well as FQFD and can switch intelligently is designed. The proposed algorithm is implemented by the second-order FLL-assisted third-order PLL tracking loop,and drives FLL and PLL alternately according as different dynamic circumstance. So the dynamic adjustability of carrier tracking loop is impoved. By four different dynamic condition experiments of fixed frequency, first power ramp frequency, second power ramp frequency and breaking frequency,the validity and stability of this algorithm is proved.