无线电工程

为满足VLBI等高精度空间测量技术对时间频率稳定度和准确度提出的更高要求,深空测控系统都配置了高性能的氢原子钟。但由于部件老化、环境变化等影响,氢原子钟输出频率会发生漂移变化,需要对此频移进行校准;同时备份原子钟需要追踪并保持与主钟的输出相位一致,必须进行相位的无损切换才能保障时频信号的连续性。分析了氢原子钟的工作原理和调频移相技术,设计了一种氢钟追踪外部授时系统进行频率漂移校准、主备钟相位无损切换的工程实施方法。应用结果表明,72 h测试时间内,与GPS相比,氢钟的稳定度由原来1.1×10-13提高到3.2×10-14,主备氢钟相位差由原来1.03o减小至0.08o,满足了VLBI长时间高精度测量的精度需求。

In order to meet the requirements of spatial measurement techniques such as Very Long Baseline Interferometry(VLBI) for high time-frequency stability and accuracy,the Telemetry Tracking and Command(TT&C) system for deep-space missions has been equipped with high-performance hydrogen-masers.Due to aging of components and environment changes,the output frequency drifts in the hydrogen-maser,which needs to be calibrated.In addition,the standby-clock needs to track the main clock and maintain the same phase.This paper analyzes technique of phase shift in frequency adjustment based on the working principle of the hydrogen-maser.A method of engineering implementation is designed for frequency calibration of the hydrogen-maser,which can track the external time system and switch phase with no loss between the main and standby clocks. As a result,compared with GPS,the stability of the hydrogen-maser is increased to 3.2 × 10-14 from 1.1 × 10-13 in 72 hours,and the phase difference in 72 hours is decreased to 0.08°from 1.03°between the main clock and standby clock,which satisfies the long-term stability requirements of VLBI.