空间相机集成测试系统的时钟同步

Time synchronization of integrated testing system of space camera

为实现空间相机地面集成测试系统中各专用设备精确时钟同步的要求,提出了一种以GPS卫星同步时钟为时钟源,将时间报文和脉冲信号相结合的综合对时方法。采用FPGA和VHDL设计了时间报文接收、脉冲对时、内部守时时钟及PCI本地控制逻辑等模块。利用Windows2000/XP下的WDM框架开发了PCI总线驱动程序,实现时统卡与专用设备之间时间信息的实时传输。设计了微秒级延时的秒脉冲作备用秒输入,解决了系统工作时因GPS卫星同步时钟意外断电引起时间信息中断的技术问题。示波器测试结果表明,专用设备之间的同步时间精度≤10μs;时间准确度≤10μs。半年运行测试验证表明,精确时钟同步系统稳定、可靠,满足空间相机集成测试系统的实时对时需要。

In order to improve the precision of time synchronization between the appropriative apparatuses of integrated testing system of a space camera,a means was designed.Based on the GPS satellite synchronous clock,it combined the serial time message and the second-pulse to adjust the time of appropriative apparatuses.The serial time message taken,second-pulse capture,internal punctual clock and the PCI local control logic modules were designed with the Field Programmable Gate Array （FPGA） and VHSIC Hardware Description Language （VHDL）.Using the WDM based on Windows 2000/XP,the PCI driver was explored to communicate the time message in FPGA to the appropriative apparatus synchronously.A microsecond-delayed second-pulse was designed to serve as a substitute to prevent the time discontinuity caused by the power broken of GPS satellite synchronous clock when it was working.The test and experiment show that both the precision and accuracy of time synchronization have reached the microsecond range,which totally satisfies the requirement of the integrated testing system of space camera for adjusting time in real time.