一种基于非线性差分运算的MSK定时同步环路

针对最小频移键控系统,首先介绍了一种基于四阶非线性运算的定时同步环路工作原理;该环路首先对信号进行非线性统计相关运算,然后计算出相关值的梯度,从而提取出时延的误差极性;接着针对该环路,结合Gardner定时同步算法提出了一种数字化定时同步环路结构;该环路分别利用差分与时间平均运算来代替求导和统计平均运算;最后针对GMSK调制系统进行了仿真验证,仿真结果证明该环路具备较好的收敛性能,并且环路不受相偏影响,能容忍的频偏范围随着信噪比的增加而变大。

A Digital Timing Tracking Loop Based on Nonlinear Differential Principle for MSK Modulations

A digital timing tracking loop for MSK （minimum shift keying） modulations is presented based on four order nonlinear operation of signal and employing the architecture of Gardner timing recovery loop. The loop first obtains a nonlinear signal by passing the received signal through a nonlinear statistical differ ential module, and then calculates the gradient of the nonlinear signal to extract the timing error polarity. In order to reduce the complexity of the loop, digital differential and time average operations are implemen ted. At last, the performance of the proposed loop is verified by means of simulation using GMSK signal. Simulation results show that the loop is not affected by phase offset, and frequency offset range that the loop can deal with would improve as the signal to noise ratio increases.