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同步数字系列 ( SDH)指针调整给支路时钟带来了幅度很大的低频抖动 ,一般的时钟同步恢复方法 (如简单的模拟或数字锁相环 )已无法将其滤除 ,为恢复 SDH中基群时钟同步 ,提出了一种新的全数字化方法——统计预测法。该方法通过对一个统计周期内欲平滑时钟与参考时钟的差异的统计 ,在下一个周期内预测出支路时钟。从该方法的原理、抖动性能的分析以及给出的计算仿真结果和实验测试结果可知 ,该方法可以有效地平滑由于指针调整和码速调整产生的很大的相位跃变 ,恢复的时钟抖动很小 ,有很好的抖动转移特性和很大的捕捉范围 ,且不需要锁相环 ,系统便于集成 ,有利于设备的小型化。
Synchronous Digital Hierarchy (SDH) Pointer adjustment brings a large amount of low frequency jitter to the tributary clock, which can not be filtered by a common clock recovery method (such as a simple analog or digital phase-locked loop) Based on the synchronization of the basic group clocks, a new all-digital method, statistical prediction, is proposed. The method predicts the branch clock in the next cycle by counting the difference between the smooth clock and the reference clock in a statistical period. From the principle of the method, the analysis of the jitter performance and the given simulation results and experimental results, it can be seen that this method can effectively smooth the large phase jump caused by the pointer adjustment and the code rate adjustment. The recovered clock jitter is very good Small, good jitter transfer characteristics and large capture range, and does not require a phase-locked loop, the system is easy to integrate, is conducive to the miniaturization of equipment.