导频脉冲载波频率的快速捕获与跟踪

针对短时导频脉冲载波频率的同步问题,提出一种快速捕获和跟踪方法.该方法采用相位推算法进行快速载波频率初估计,完成频率的捕获.相位推算法首先利用最小二乘法估计实采样点的相位,再应用相位解卷、一元线性回归和最小二乘法拟合求取信号频率的估值,其测频精度优于常用的Prony算法,在高信噪比情况下逼近实正弦信号的Cramer-Rao界.应用数字下变频和Kay算法实现频率的跟踪,通过建立仿真模型,验证其跟踪精度优于叉积自动频率控制环.在给出的设计实例中,对于脉宽为1ms的导频脉冲,在信噪比大于13dB的情况下,环路频率跟踪的最大误差小于3Hz. 

Rapid frequency acquisition and tracking for pilot pulse carrier

To aim at short-time pilot pulse carrier-frequency synchronization,a rapid acquisition and tracking approach was proposed.In this approach,a phase deduction frequency estimator(PDFE) was employed to perform initial carrier-frequency coarse estimation and accomplish frequency acquisition in short time.The PDFE obtains the phase angle estimation of real signal samples by least square method,and then computes the frequency value by phase unwrapping,unary linear regression and least square fitting.Its estimation accuracy exceeds Prony's method and its estimation error normalized variance approaches the Cramer-Rao bound of real sinusoid signal at high signal-to-noise ratio.Digital down conversion loop and Kay's method were adopted to perform frequency tracking,its performance exceeds cross product automatic frequency control(CPAFC) loop.The tracking accuracy was evaluated by simulation.An example was given,its maximum frequency tracking error is not more than 3 Hz at input SNR above 13dB for 1ms pilot pulse width.