射频拉远系统中的时钟同步技术

Clock Synchronization Technology in Remote Radio System

针对射频拉远系统中基带控制部分和射频拉远单元之间的时钟漂移问题,提出了一种利用锁相环进行时钟同步的技术.该技术利用锁相环的特点,通过跟踪时钟漂移并对时钟信号进行预补偿来达到抵消时钟漂移的目的.分析了漂移的产生和影响以及补偿方案的可行性,设计并制作了集成在一块4层印刷电路板中的时钟同步模块.测试结果表明:加入时钟同步模块的时钟信号频率稳定度可达到1×10-12,较之无同步模块提高了4个数量级;对于10,km和100,km单程光纤链路,该方案能达到同样的效果.可见,采用该技术可以在较大的动态范围内补偿时钟漂移,从而提高时钟信号的频率稳定度.

A clock synchronization technology based on phase-locked loop was proposed to deal with the clock driftproblem that occurs between the radio server and the remote radio unit in remote radio system. The technology takesadvantage of the features of phase-locked loop and achieves the goal of cancelling out the clock drift by tracking theclock drift and pre-compensating the clock signal. The research into the generation and impact of the drift was fol-lowed by an analysis on the feasibility of the compensation plan. Meanwhile, the clock synchronization module inte-grated in a four-layer printed circuit board was fabricated. And it was proved in the experiment that the clock fre-quency stability could reach 1 x 10 12 with the functioning of synchronization module, achieving improvement of 4orders of magnitude. And the result was about the same for 10 km and 100 km one-way fiber link. Therefore, thistechnology is able to eliminate the clock drift in a large dynamic range, and enhance the clock frequency stability.