飞秒稳定度事件计时器设计及激光时间比对应用

Design of Event Timer with Femtosecond Stability and Its Application in Laser Time Transfer

事件计时器可实现输入事件时刻的高精度、高稳定测量,且工作频率不受测量间隔限制,是星地激光时间比对中不可或缺的设备.为满足飞速发展星载原子钟的评估要求,对星地激光时间比技术中激光发射、到达和返回时刻的测量提出亚飞秒稳定度和皮秒精度需求.采用FPGA配合计时芯片THS788开发了高精度事件计时器,测量精度约8 ps,非线性误差皮秒级,测量频率大于10 kHz;将基准时钟分频后作为校准信号,实现时延漂移的实时标校,时刻测量稳定性提升5倍以上.将该计时器应用在星地激光时间比对载荷,载荷测量稳定性(Time DEViation,TDEV)优于0.07 ps@300 s和0.84 ps@1 day.计时器达到国际主流产品A033-ET水平,既满足10-18量级准确度原子钟的时频传递需求,又可用于毫米级精度卫星激光测距,具有较好的推广应用价值.

The event timer can realize high-precision and high-stability measurement of the input event time,and the operating frequency is not limited by the measurement interval.It is an indispensable device for satellite-to-ground laser time transfer.In order to meet the evaluation requirements of the rapid development of spaceborne atomic clocks,sub-fem⁃tosecond stability and picosecond accuracy are proposed for the measurement of laser emission,arrival and return epochs in the laser time transfer technology.A high-precision event timer is developled by using FPGA and timing chip THS788.Its measurement accuracy is about 8 ps,the nonlinear error is less than 1 ps,and the measurement frequency is greater than 10 kHz.The reference frequency divided signal is used as the calibration signal to realize the real-time calibration of the delay drift and 5 times of improved measurement stability,so that the time deviation(TDEV)is better than 0.07 ps@300 s and 0.84 ps@1 day which applied in payload of China space station.The performance of the developed event timer reaches the level of the international mainstream product A033-ET,which not only meets the time-frequency transfer requirements of atomic clocks with 10-18 level accuracy,but also can be used for millimeter-level precision satellite laser ranging,which has good promotion and application value.