基于实时调节GPS射频前端采样周期的INS辅助GPS组合导航方法

INS-aided GPS navigation methods based on real-time adjustment of sampling-period of GPS RF front-end

为了提高GPS卫星接收机在高动态环境下的跟踪能力,提出了一种基于GPS射频前端采样周期实时调节的INS辅助GPS组合导航方法。首先通过组合滤波器将INS导航信息和GPS导航信息进行融合,修正INS导航信息误差。然后利用修正后的INS导航信息和GPS导航电文,实时计算出载体相对于每颗卫星的多普勒频移,并将得到的多普勒频移换算为GPS中频信号载波的波长变化。最后根据载波的波长变化实时调节GPS接收机射频前端ADC的采样时间间隔,补偿因为多普勒频移导致的中频数字信号采样点变化,隔离多普勒频移对GPS接收机跟踪环路的影响。仿真结果表明,此方法可以在不改变传统GPS接收机跟踪环路结构的前提下,显著提升GPS接收机的高动态性能,即使在多普勒频移变化率为5000 Hz/s的情况下,GPS跟踪环路仍能可靠工作。

A novel INS-assisted GPS navigation method based on real-time adjustment of the sampling-period of GPS RF front-end is developed to improve the tracking performance of GPS receiver in high dynamic condition. At first, a loosely-coupled INS/GPS integration system is used to correct the navigation errors of INS. Then, the Doppler shifts of each satellite channel are calculated with corrected INS navigation information and GPS ephemeris. After that, the Doppler shifts of each satellite channel are converted to the corresponding wavelength variations of IF (Intermediate Frequency) carrier wave. And a control signal is generated according to the variations of wavelength to control the sampling frequency of ADC in RF front-end. At last, the variations of sampling points due to Doppler shift in digital intermediate-frequency signal are removed by adjusting the ADC sampling frequency. Simulation results show that this INS/GPS integration method could improve the high-dynamic performance of GPS receiver, and does not need to do any modification to traditional GPS tracking-loop structure. The tracking-loop could track the carrier wave closely even if the rate of Doppler shift is as high as 5000 Hz/s. ©, 2015, Editorial Department of Journal of Chinese Inertial Technology. All right reserved.