连续相位调制的定时-频偏联合估计方法

Joint timing and carrier frequency estimation algorithm for continuous phase modulated

针对连续相位调制信号的同步问题,研究了一种定时-频偏联合估计算法.算法分3步实现:(1)对接收基带信号差分并平方,得到四阶非线性变换值;(2)求其二阶统计量;(3)基于该统计量联合估计定时偏差和载波频偏.通过改变载波频偏值及参与二阶统计量计算的符号数,对定时同步及频偏估计性能进行研究.在加性高斯白噪声信道及Rice慢衰落信道下分别进行仿真.加性高斯白噪声信道仿真表明,算法在载波频偏达到15%符号率条件下仍有出色同步性能,当参与估计的符号数等于64时,定时偏差和频偏均方误差分别达到10-6及10-5以下;低信噪比不影响算法定时恢复性能.Rice慢衰落信道仿真表明,算法具有一定的抗衰落能力,适当改变Rice信道模型参数能提升其性能.算法采用非数据辅助方式及前馈结构,同步捕获快速,实现简单,适合于突发通信.

A joint estimation algorithm of timing nization problem of continuous phase modulated and carrier frequency was presented to solve the synchrosignals. The algorithm was divided into three steps.（1） perform a fourth-order nonlinear transformation by differentiating and squaring the received baseband signal; （2） Calculate the second-order statistics of the transform value; （3） jointly estimate the timing recovery and carrier frequency based on the calculated statistics. By changing the carrier frequency and symbol numbers required for estimation, the algorithm performance was investigated. Simulation under additive white Gaussian noise（AWGN） channel shows, that in presence of a frequency drift as large as 15% symbol rate, the timing recovery error and mean square error of frequency estimation can decrease to 10^-6 and 10^-5 separately when using 64 symbols for estimation; and that the algorithm is robust under low signal-tonoise ratio circumstances. Simulation under Rician slow fading channel shows that the algorithm can stand such fading and improve its performance by changing channel parameters. The algorithm features with quick synchronization and easy implementation with non data-aided method and feedforward structure, and suits well for burst mode communications.