基于带宽调整的两种混合载波跟踪环路研究

Research on Two Kinds of Hybrid Carrier Tracking Loop Based on Bandwidth Adjustment

针对高动态导致载波复现频率与实际载波频率相差较大的问题,锁频环和锁相环已无法满足环路的跟踪需求,依据频率判决因子实现三阶锁频环辅助四阶锁相环和四相鉴频器之间相互切换的2种混合载波跟踪环路算法;在三阶锁频环辅助四阶锁相环的基础上,通过相位判决因子完成对载波环带宽的动态调整。结果表明,在动态为5000/150 g/120 g、载噪比为42 dB/Hz、跟踪初始多普勒为300 Hz时,基于带宽调整的2种混合载波跟踪环路能准确地剥离出电文信息,而单一的三阶锁频环辅助四阶锁相环载波跟踪环路不能实现;当跟踪初始多普勒为0时,环路稳定跟踪后加入25/20 g/20 g的动态,基于带宽调整的2种混合载波跟踪环路可以重新完成稳定跟踪并剥离出电文信息,而三阶锁频环辅助四阶锁相环载波跟踪环路直接失锁;低载噪比下的基于带宽调整的2种混合载波跟踪环路的跟踪相位误差方差相对较小、跟踪精度较高。

In view of the fact that the carrier reproduction frequency is different from the actual carrier frequency due to high dynamic,the frequency-locked loop and the phase-locked loop can’t meet the tracking requirements of the loop.According to the frequency decision factor,two kinds of hybrid carrier tracking loops that are switched between third-order frequency-locked loop assisted the fourth-order phase-locked loop and the four-phase frequency discriminator are realized.On the basis of the third-order frequency-locked loop assisted fourth-order phase-locked loop,the bandwidth of the carrier loop is dynamically adjusted by the phase decision factor.The simulation results show that when the dynamic frequency is 5000/150 g/120g,the carrier-to-noise ratio is 42 dB/Hz and the initial Doppler of tracking is 300 Hz,the two hybrid carrier tracking loops based on bandwidth adjustment can accurately strip out the message information,while the single third-order frequency-locked loop assisted the fourth-order phase-locked loop can not.When the tracking initial Doppler is 0 and 25/20 g/20g dynamic is added after the loop is stably tracked,the two hybrid carrier tracking loops based on bandwidth adjustment can re-complete the stable tracking and strip off the message information,while the third-order frequency-locked loop assisted the fourth-order phase-locked loop carrier tracking loop would directly loss lock;Moreover,the tracking phase error variance of the two hybrid carrier tracking loops based on bandwidth adjustment under low carrier-to-noise ratio is relatively small and the tracking accuracy is high.