MLE辅助PLL的高动态GPS载波跟踪

MLE Assisted PLL Based High Dynamic GPS Carrier Tracking

针对传统锁频环(FLL)鉴别器存在一步延迟效应和近似误差的问题,提出一种基于极大似然估计器(MLE)辅助锁相环(PLL)的高动态载波跟踪环路。该方法从极大似然估计理论入手,构造多普勒频移的非相干极大似然代价函数,采用非迭代估计方法求取各通道多普勒频移偏差的极大似然估计,与PLL进行融合滤波并计算频率修正量,进而控制本地数控振荡器(NCO)完成载波跟踪。仿真结果表明:在同等环路阶数和滤波器带宽条件下,新方法的响应速度、动态忍受力优于基于FLL辅助PLL的方法,可以跟踪加加速度达到100g/s的超高动态信号。

To reduce the one-step delay effect and approximation error caused by the conventional frequency lock loop（ FLL） discriminator,a new tracking loop integrated Maximum Likelihood Estimation（ MLE） with phase lock loop（ PLL）is proposed. To begin with the principle of MLE,this algorithm firstly establishes a non-coherent maximum likelihood cost function to produce the MLE of Doppler frequency error for each channel,and then the frequency error is added to a PLL to get precise frequency estimation through a loop filter. Lastly,the numerical controlled oscillator（ NCO） is used to adjust the local carrier frequency to accomplish the carrier tracking. Simulation results show that compared with FLL assisted PLL tracking loop,the new method performs well in response time and dynamic stress under the condition of the same filter bandwidth and loop order,and is capable of tracking extremely high dynamic signal with a sudden jerk up to 100 g / s.